# Are lathe tool carbide inserts supposed to be sharp?



## m12lrpv (Oct 30, 2021)

I've got a tu2004v lathe inbound (they're on backorder) and it's my first lathe. I'm a hobbyist and not a trained machinist so I've never been educated in any of this stuff. I suppose you could say I'm somewhat of a stereotypical newbie having sat through a ton of you tube videos trying to learn all I can. I do however have a lot of grey in my beard and a shed full of tools that do get used so to my credit I'm smart enough to have not killed myself doing something stupid using them. I would like to continue that pattern 

Following that stereotypical newbie process I've bought one of the typical carbide insert tooling sets that you get from the usual chinese import sites.  (And for those that always choose to chime in about HSS I have some of that also and will grind it up when I get to it).

Back to the carbide inserts though, I'm genuinely surprised at how blunt most of the inserts are. I can easily push my finger onto the cutting edge without cutting myself. Except for the threading inserts and the grooving tool which do feel a bit sharp.

My past experience tells me that blunt tools can dangerous tools so I want to make sure that this is normal before I try and turn some steel with them and potentially do some damage.

I do understand that different materials require different insert types/grades/sharpness. I have a small cnc and all the milling cutters i have for it (even the carbide ones) are extremely sharp.
From the CNC I know that Aluminum, plastic and wood need sharp cutters and from drilling I know that steel likes sharp drill bits but maybe that's a HSS drilling thing only. I've never drilled steel with a carbide.

So are these cutter inserts meant to be sharp (drill bit sharp) or is the rounded looking top of the cutting edge actually normal? Am I worrying over nothing?

I know straight up that I wouldn't go near aluminum with these. Plastic I expect will be safe to try it on because failure there won't damage anything other than the plastic. I expect that blunt inserts on steel are probably just going to chatter and/or screech loudly, like trying to drill with a blunt drill bit or a drill on reverse.

If there's anything I think that the typical youtubers who have machinist backgrounds and training leave it's it's the really simple stuff like the answers to questions like these


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## Zeb (Oct 30, 2021)

Carbide inserts do tend to feel that way. You should have zero problem with aluminum and you can push them much harder than HSS, as the heat won't touch them. Just make sure the inserts are secure but not overtorqued.


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## m12lrpv (Oct 31, 2021)

Thanks. I'll give it a shot as is and see how they go.


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## Mechanicboy (Oct 31, 2021)

If you want a fine and detailed work at material who are not possible with insert carbide tool, use HSS tool who are easy to form with bench grinder and keep sharp with hone stone. To keep "long life" of tools --> select cutting speed depending om which material and diameter.


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## Jasonb (Oct 31, 2021)

Most generic sets tend to have a general purpose insert with a code **MT Where the ** refers to the shape and the M the tolerance. For fine work on steel,  and all work on brass, bronze, stainless, plastics and Aluminium you would do well to get some **GT inserts which have a higher tolerance that is achieved by grinding or polishing and typically have a bright "chrome" look rather than the golden colour of the **MT. This makes them much sharper so they cut better without loading up the small hobby machines and less likely to weld aluminium to the edge. A 0.4mm tip radius will do for most things.


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## Richard Hed (Oct 31, 2021)

There are many different shapes of carbide bits.  I generally use the long-nosed diamond shape for a lot of cutting but there are other shapes I also use.  Triangle, square, rectangular and even round ones for certain -purposes.  You should try different types for different purposes/materials.  Also, many peeps recommend giving the carbides a touch up with a hand stone.  I find this helps with difficult materials, other wise , I don't bother.  Also, it really IS a necessity that the cutting speed is much higher or you can easily crack the carbides.  Also NEVER turn your chuck backwards with the carbide touching the work--you are almost guaranteed to break it.  I know, I've done it too many times and am sure I will do it again.  

Oddly, I just was reading a perfect beginner book, thimpfking it might have somethign useful for me in it but it didn't.  It's a great book, but told me nothing new for myself.  Horribly, I went to look for it on my computer and can't find it.  However, there are lots of places to get good books on the subject.

this is Z-library:  [Magazine] Scientific American Mind. Vol. 19. No 6 |  | download

Here is Archive . org:  Free Books : Download & Streaming : eBooks  and Texts : Internet Archive

and also PDF drive:  The Gospel of Barnabas by Lonsdale Ragg - PDF Drive

These all just happen to be on subjects I was interested in, you can do your own searches, of course.  There are others too, but I thimpfk these three are the best.

HSS bits might be a better general usage for you if you have a small lathe.  I don't know waht a tu2004v is.  Do you have a photo?  be sure to get a cou0ple sets of protective eye-wear.  It's the num,ber one essential safety tool.  Also, you can read about various of us who have NOT LOST THEIR FINGERS yet! but have had various accidents that it is a good thing to learn from.  Don't wear baggy long sleeves particularly on yuour left arm.  Never leave the chuck key in the chuck unless you want it as a decoration stuck in your head.  

What kind of hobby work do you intend?


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## barryc43 (Oct 31, 2021)

Might I suggest that you buy a bit of nylon bar for your first turning adventures?  It will allow you to see how the lathe and various tools function without danger of doing any damage to yourself, the lathe and of course the tooling?


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## Bushranger (Oct 31, 2021)

Just my 2 bobs worth, but I'm using a 1970 Hercus 9AR most of the time now.  Shop made toolholders with no built-in back rake.  Sick of grinding the rake into HSS bits, bought some brazed carbide tools to run on the lathe.  They had to be sharpened before use, but work a treat.  Might be worth considering something similar.  Again, just my opinion.


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## simonbirt (Oct 31, 2021)

I would echo what has been said, inset tooling is really not intended for hobby lathes. Watching YouTube videos can be helpful, but there is an awful lot of bad practice being proglamated. Inset tooling is intended to be used on rigid machines using high rates of feed and speed together with flood coolant; all difficult to achieve for hobbyist. 

You say that you have some HSS to experiment with, I would make that my starting point, once you understand the geometry and can grind it into a working tool you will have a much better understanding of machining. It is easy to grind, in fact a 1” belt sander is great for shaping HSS, better in many ways to a bench grinder. 

Brazed carbide tooling is a good option, but it is hard to grind and easy to chip. 

Have a look at some of the books by the likes of George Thomas, what you will see is simple tooling producing outstanding fits and finish. It is also very satisfying to see a tool you have made moving metal.


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## Jules (Oct 31, 2021)

Carbide tends to be used on large rigid machines. They are designed to remove metal at high rates and just bulldoze there way into the material and break nice chips. 
Most hobby lathes aren’t really rigid or heavy enough but you can still turn metal with them. 
I tend to use inserts designed for turning aluminium because they are much sharper and load the machine less. 
You can also try a smaller radius tip as that will increase the effective cutting pressure. 
stay safe and have fun.


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## clockworkcheval (Oct 31, 2021)

Cutting metal is in close-up not really cutting but a discontinuous rip-off proces. The sharper the tool the finer the rip-offs, the lower the forces and the smoother the resulting surface. The cutting speed of carbide inserts is roughly up to three times the cutting speed of high speed steel HSS. And this higher speed gives a much smoother rip-off proces. Compare with plowing snow at low speed and high speed. So the sharpness of the insert will not affect the process much, and a slightly less sharp cutting edge is stronger and more wear resistant and thus allows for bigger chips, that produce higher cutting forces. For small precision parts it is however beneficial to give the insert a really sharp cutting edge using a fine diamond grinding/honing wheel.
The use of carbide inserts depends fully on those higher cutting speeds. Your lathe tu2004v has I believe a maximum spindle speed of 2500 revs. This means that you have a good carbide cutting speed for steel down to diameter 20 mm, and for brass and aluminum down to diameter 40 mm. For diameters smaller than this you would be well advised to switch to HSS tooling. The HSS cutting speed for steel is OK down to diameter 6 mm and for brass and aluminium down to diameter 12 mm. Several members of my horological society use a small second lathe capable of high revs like up to 15.000 - 20.000 revs for the small parts with diameters to be cut say from 1 mm up to 10 mm.
In my own workshop I have pampered myself with a Schaublin 102 VM lathe which goes up to 3000 rpm with a frequency controller, a Myford Super Seven of similar size which also with a frequency controller goes up to 5000 rpm and a TAIG with a DC motor and DC control that goes up to 18.000 rpm spindle speed.
Overall it is my strong believe that the hobby machinist and the hobby equipment reflect the workshop practices of 60 years ago. So it is very helpful if you have acces to a workshop engineering manual of about the 1960's.


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## Ken I (Oct 31, 2021)

Carbide inserts almost never have "razor sharp" edges as they chip too easily then - they are even rumbled after sintering to remove sharp edges.
The cutting edge radius is obviously going to "rub" but as the depth of cut becomes bigger, this become less of an issue.






So insert tools require greater depths of cut, higher speeds and much greater machine power and rigidity to get good results. Hobby machines often don't have the power or rigidity to drive insert tools very well.

https://www.researchgate.net/figure...ed-cutting-edge-images-of-edge_fig1_257336237

Light "finishing" cuts with carbide insert tools generally doesn't work - you need to work your way down to size taking cuts that develop a good finish and your last two passes must be at the same depth of cut (let's say 0.5mm) - such that when you are aiming for Ø25mm diameter you need to go to Ø27 then Ø26 and finally to Ø25 - this is so you get to size with the same reaction forces and cutting dynamics. Change depth of cut on your last pass and you are almost certainly going to get it wrong.

Imagine you aimed for Ø 27.00 but got Ø 27.05 - dial in Ø 0.53 depth of cut and you get (say) Ø 26.02 - so for the final cut dial in 0.54 depth and you should come out at Ø 25.00.

Hobby machining often requires light finishing cuts and for that you need "razor sharp" edges - use HSS or brazed carbide properly sharpened and polished.

Regards, Ken


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## m12lrpv (Oct 31, 2021)

Thanks guys.
I'm fully expecting that I'm going to end up with a draw full of different cutters. After all that's what hobbies are all about. Filling your shed with stuff.
I had actually been somewhat dismissive about the brazed carbide cutters but i've seen a few references to them being able to be sharpened so I'll probably get some of them too.
At the moment though I was just wanting to get a handfull of tools to enable me to get started with a few small cuts while I worked out what it was i really needed. Buying the insert holder kits is really just buying the holders with a couple of inserts thrown in so it's a safe option because even if the inserts that come with it are garbage they're only temporary.

I've been looking at lathes for a long time but have never been able to justify it. I've been able to make enough $$$ from other hobbies to justify the spend so I'm finally making the leap. I could never justify buying the lathe i really want (a gunsmithing lathe) but this will do to get me started.


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## Jasonb (Oct 31, 2021)

I find I can take of a 0.001" depth of cut with a DCGT in steel. I could not easily do that with a DCMT or CCMT particularly on long slender work like crankshafts or valve stems where the "blunter" carbide tends to deflect the work or cause chatter when the required deeper cut is taken.

Probably best on full screen


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## clockworkcheval (Oct 31, 2021)

Asking about the economic justification of hobby machinetools is asking the wrong question, as I often have to explain to my resilient wife Eleonora.


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## Steamchick (Oct 31, 2021)

I like the expression "resilient wife"... we all need one of those!
I sometimes wonder at the motivation of these girls to remain wives of hobbyists and engineers... But understanding sub-nuclear particles and black-holes is easier than delving into the minds and motivation of Wives and Girlfriends.
K2


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## Steamchick (Oct 31, 2021)

Bucket-loads of information here... a lot I was never taught. 
But I was taught in the 1960s, on machines that had home-ground "tool-steel" tools and speeds in the hundreds, not thousands. For machine stiffness versus size of cut, it was always the workpiece that was least stiff, so cuts were adjusted to stay below distortion limits of the workpiece.
That is not appropriate training for HSS or carbide tool use.
Also the huge lathes that I used as an apprentice (biggest was a 16 ft long bed, 18" swing) do not compare to hobby lathes that you can twist round your little finger with a heavy cut... so cuts are often limited by the combined machine and work-piece distortion that causes inaccuracies as explained by Ken - post #12 above.
Thanks all. Education comes every day...
K2


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## L98fiero (Oct 31, 2021)

Ken I said:


> Carbide inserts almost never have "razor sharp" edges as they chip too easily then - they are even rumbled after sintering to remove sharp edges.
> The cutting edge radius is obviously going to "rub" but as the depth of cut becomes bigger, this become less of an issue.
> View attachment 130441
> 
> ...


Typically with carbide you shouldn't take a cut less than the insert tip radius though if you are finishing with the xxGT inserts intended for non-ferrous metals, because of the sharpness and high top rake you can take smaller cuts.


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## Steamchick (Oct 31, 2021)

I have also used a diamond disc or hand dresser to put an edge on carbide tips for finer machining and finishing cuts. (But didn't know the "Why?"!).
K2


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## ChazzC (Oct 31, 2021)

barryc43 said:


> Might I suggest that you buy a bit of nylon bar for your first turning adventures?  It will allow you to see how the lathe and various tools function without danger of doing any damage to yourself, the lathe and of course the tooling?



I suggest Delrin™ (Acetyl) rod for first attempts, Nylon can be gummy.


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## ChazzC (Oct 31, 2021)

There is a supplier here in the U.S. that manufactures T-15 HSS inserts that work beautifully for aluminum and steel on a 7" x 12"/14"/16" mini-lathe:

Standard and Specialty Inserts

When the inserts get dull, they can easily be sharpened by rubbing them upside-down on an oil stone. They also offer high quality holders:

Tool Kits

You will still want to have HSS blanks so you can grind special tool bits if the need arises, but their #8 3/8" kit will take care of 90% of your needs:

Kit #8 3/8 inch Turning (C) Right Hand Left Hand and Boring Bar














m12lrpv said:


> I've got a tu2004v lathe inbound (they're on backorder) and it's my first lathe. I'm a hobbyist and not a trained machinist so I've never been educated in any of this stuff. I suppose you could say I'm somewhat of a stereotypical newbie having sat through a ton of you tube videos trying to learn all I can. I do however have a lot of grey in my beard and a shed full of tools that do get used so to my credit I'm smart enough to have not killed myself doing something stupid using them. I would like to continue that pattern
> 
> Following that stereotypical newbie process I've bought one of the typical carbide insert tooling sets that you get from the usual chinese import sites.  (And for those that always choose to chime in about HSS I have some of that also and will grind it up when I get to it).
> 
> ...


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## Makerphil (Oct 31, 2021)

m12lrpv said:


> Thanks guys.
> I'm fully expecting that I'm going to end up with a draw full of different cutters. After all that's what hobbies are all about. Filling your shed with stuff.
> I had actually been somewhat dismissive about the brazed carbide cutters but i've seen a few references to them being able to be sharpened so I'll probably get some of them too.
> At the moment though I was just wanting to get a handfull of tools to enable me to get started with a few small cuts while I worked out what it was i really needed. Buying the insert holder kits is really just buying the holders with a couple of inserts thrown in so it's a safe option because even if the inserts that come with it are garbage they're only temporary.
> ...


I use carbide insert on my mini lathe without any problems, just try them and gain some confidence. It’s a better use of your time rather than grinding tools for your lathe.


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## Mechanicboy (Oct 31, 2021)

Makerphil said:


> I use carbide insert on my mini lathe without any problems, just try them and gain some confidence. It’s a better use of your time rather than grinding tools for your lathe.



Are you sure we can get rid of the HSS tool? Nope..


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## Richard Hed (Oct 31, 2021)

Generally,. I use carbides but often I have to have a specially shaped tool, so naturally, it's HSS and if it's particularly difficult material, I might silver solder a shaped carbide to do the job.  I do, however, have a machine that is large and heavy enough to do heavy jobs for amateurs.  I can also do pretty small jobs like threading a 6-32 specialty bolt.  Very nerve wracking, however.  I have an Enco 9/20 which simply does not go slow enough to cut tiny threads like that--I cannot shut it off fast enough.  The Grizz G4003G is nice enough to go 70 rpms, wish it were 50, but this is slow enough to cut tiny threads and be able to switch the threading lever to off.  Yeah, yeah, I know, turn the thread tool over and go in reverse.  Haven't got around to that, and, of course, this will take a specially ground HSS bit.


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## Zeb (Nov 1, 2021)

I work exclusively in HSS/W1 for that reason. I want to shape all my stuff (gear cutters, graving chisels, etc) and all my cuts are light.


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## Makerphil (Nov 1, 2021)

Mechanicboy said:


> Are you sure we can get rid of the HSS tool? Nope..
> 
> View attachment 130450


I wasn’t suggesting that HSS tools should never be used but for most of the time carbide tools work just fine especially when you are just starting out machining for the first time.


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## Richard Hed (Nov 1, 2021)

Makerphil said:


> I wasn’t suggesting that HSS tools should never be used but for most of the time carbide tools work just fine especially when you are just starting out machining for the first time.


On my Enco (really just a toy), HSS workt better than carbides but I used both.  It sitsoff to the sidenow as I blew the half nut trying to cut 8 TPI for the nose on the spindle.  Well, I have a better lathe now.


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## Jasonb (Nov 1, 2021)

Mechanicboy said:


> Are you sure we can get rid of the HSS tool? Nope..



One can usually find what is wanted in carbide 





HSS and carbon steel does still have its uses but I would not write off Carbide completely and still use both where it's the better option for the job in hand.

The other big advantage of using carbide on the hobby machines is that the variable speed does not work so well at the very low speeds needed as the diameter of work goes up as they runs out of guts so using carbide allows the motor to run faster and stay in it's power band and the cooling fan can keep a decent air flow. Typical example if I were turning say a 9" cast iron flywheel it would stall the spindle at HSS speeds but happy to run at 300rpm with carbide and a fine feed with the added bonus of not worrying about the skin or hard spots taking the edge straight off HSS.


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## GrahamJTaylor49 (Nov 1, 2021)

ChazzC said:


> I suggest Delrin™ (Acetyl) rod for first attempts, Nylon can be gummy.


Picked up a length of Delrin at a boot sale. The bloke selling it didn't know what it was. It was 2 1/2" diameter by 4 foot long and even after telling him what it was he wouldn't take more than £3.00 for it. I ended wandering around Ashley Heath boot sale for about 2 hours carrying this lump around. Still was a great buy.


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## ajoeiam (Nov 1, 2021)

Makerphil said:


> I use carbide insert on my mini lathe without any problems, just try them and gain some confidence. It’s a better use of your time rather than grinding tools for your lathe.



You CAN use carbide insert tooling without any problems. 
If you understand what you're doing you can grind tools for your equipment that are quite expensive to buy - - - - if you can. 
Understanding how to grind tools also allows you to modify existing. 
I've cut a number of different plastics (generic term use) using carbide - - - - its a lot easier to do so using ground cemented carbide. 

For one, I would not want to relinquish my self developed tooling. 
(There comes to be a lot of freedom with being able to make your own tooling. 
That freedom becomes very very useful when you start workikng with 'interesting' materials (ones that most 'hobbyists' don't touch.)


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## Ozwes007 (Nov 1, 2021)

Just get some carbide tips to suit plastic and aluminium mate, they are extremely sharp and cut aluminium and plastics like butter. Use them all the time.


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## Makerphil (Nov 1, 2021)

ajoeiam said:


> You CAN use carbide insert tooling without any problems.
> If you understand what you're doing you can grind tools for your equipment that are quite expensive to buy - - - - if you can.
> Understanding how to grind tools also allows you to modify existing.
> I've cut a number of different plastics (generic term use) using carbide - - - - its a lot easier to do so using ground cemented carbide.
> ...


I think we were responding to someone who has very little experience of machining.


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## minh-thanh (Nov 1, 2021)

Personally, I prefer using HSS
I bought some carbides, but rarely used, only 1-2 times
Sometimes I  use broken drills or taps as turning tools
   An interesting video :


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## Mechanicboy (Nov 1, 2021)

minh-thanh said:


> Personally, I prefer using HSS
> I bought some carbides, but rarely used, only 1-2 times
> Sometimes I  use broken drills or taps as turning tools



I used old drills, carbon steel,  old files and some broken screwdriver who are hard enough for aluminium and softer metals when I can shape the tool that is not available in carbide tools. Jigsaws that contain HSS used as parting tool. 

Look at the photo in my comment # 24: 4 mm drill that I shaped to make ring grooves for locking ring for piston bolt and the other is a 6 mm D-bit reamer to smooth out the hole. Also the homemade tools are "universal" tool to form what one want to form the product in the lathe. But I'm use carbide tools too if I need to make coarse work to nearest measure before finished to right measure with other tools, some time if cast iron has hard spots who are impossible to work with the tools than carbide tool.


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## awake (Nov 1, 2021)

For me, it comes down to cost - I've done nearly all my hobby machining with HSS simply because it is so much cheaper. I do have a little bit of carbide tooling, but I use that primarily for machining hardened materials.


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## SmithDoor (Nov 1, 2021)

I agree 

Dave 



minh-thanh said:


> Personally, I prefer using HSS
> I bought some carbides, but rarely used, only 1-2 times
> Sometimes I  use broken drills or taps as turning tools
> An interesting video :


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## wazrus (Nov 2, 2021)

Carbides are great for high stock removal rates and are, I think, a commercial proposition. Having said that, I have lots of 'em, both insert types and brazed, many of which I've brazed myself. But I also have heaps of HSS and wouldn't be without it. Using carbides dictates a much higher load on your machine, so if carbides are necessary - particularly the inserts - I switch to a much heavier machine. The little 7"x14"s really aren't robust enough to 'load' carbides and make 'em cut the way they should. I haven't used carbides at all on the little ones. Early in the piece, grinding tooling was one of those things I did plenty of. HSS holders are a bit of a rarity these days, but they are still available. I have solid HSS bars up to 20mm square and some of the profiles I've ground are really finicky. I regularly 'touch up' carbide inserts when they get duller than as supplied, for this, I use a 'green grit' wheel. Putting on a really keen edge often does the goods, as carbides seem never to be as 'sharp' as it's possible to grind HSS. The load differences are readily 'feelable', through the saddle handwheel. With HSS, it's all a function of the tool rakes, which may be generous. Carbide rakes are pretty much non-existent, although negative rake tooling can be very useful. With my heavier machine, cuts of .25" are commonplace, both with carbide and HSS: sometimes, I push HSS to the limit and it still cuts when red hot. Enough!!


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## Makerphil (Nov 2, 2021)

I think you will find that carbide tools work fine on a mini lathe especially if you use the ones for non ferrous materials. You should give it a go.


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## Bazzer (Nov 2, 2021)

m12lrpv said:


> I've got a tu2004v lathe inbound (they're on backorder) and it's my first lathe. I'm a hobbyist and not a trained machinist so I've never been educated in any of this stuff. I suppose you could say I'm somewhat of a stereotypical newbie having sat through a ton of you tube videos trying to learn all I can. I do however have a lot of grey in my beard and a shed full of tools that do get used so to my credit I'm smart enough to have not killed myself doing something stupid using them. I would like to continue that pattern
> 
> Following that stereotypical newbie process I've bought one of the typical carbide insert tooling sets that you get from the usual chinese import sites.  (And for those that always choose to chime in about HSS I have some of that also and will grind it up when I get to it).
> 
> ...



My experience is that the smaller the machine tool the more critical having good cutting tools is to getting good results.

Don't believe any of the hog wash you hear about carbide only being for production machining, it is just about the most ingenuous advice that is pushed around on model engineering forums.

You say that you are a beginner, the last thing you need is doubts that your cutting tools are wrong, buy a decent tool holder and buy a few known quality inserts for general use. Buy the biggest and stiffest tool holder that will fit in the tool post, ridgity (or lack of) is the enemy in small machine tools, do everything you can to win back ridgity.

HSS definitely has a place as you can grind custom tools, but you can pick up this experience once you have gained confidence of machining in general. HSS although is truly useless on some materials such as abrasive composites or some metals (high silicone aluminium being one that springs to mind)

B.

PS when looking for the spec. on your lathe I found this quite interesting site.

The Optimum D180 / TU2004V Mini Lathe Blog is here!


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## Makerphil (Nov 2, 2021)

Bazzer said:


> My experience is that the smaller the machine tool the more critical having good cutting tools is to getting good results.
> 
> Don't believe any of the hog wash you hear about carbide only being for production machining, it is just about the most ingenuous advice that is pushed around on model engineering forums.
> 
> ...


A very sensible and balanced view on carbide tooling. Of course many of the replies on this thread are assuming that a first time lathe buyer has a grinding wheel available.


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## ajoeiam (Nov 2, 2021)

Makerphil said:


> I think we were responding to someone who has very little experience of machining.



Without the backstory - - - - well your post reads as though you 'are' suggesting against using one's own developed tooling. 
Dunno how many times I've read on this forum of people muttering about sharpening tooling. 

Machining is not a solitary skill. 
It is necessary to combine a bunch of other skills (likely also new) together to effectively practice machining.


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## Shaun free (Nov 2, 2021)

As far as tooling goes the Carbide inserts generally have a radiused nose and specific angles for different types of material and as mentioned earlier are generally used on CNC machines that have much tighter tolerances and are more rigid allowing for deeper more controlled cuts with feeds and speeds calculated with the surface feet per minute adjusted with the diameter changes. For a home manual lathe you will get better results cheaper with the brazed carbide and high speed steel. 

I really suggest getting the Machinist handbook. It will have any information you may need and then some. Its the bible for machinist and I use mine all the time.


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## Ozwes007 (Nov 2, 2021)

Shaun free said:


> As far as tooling goes the Carbide inserts generally have a radiused nose and specific angles for different types of material and as mentioned earlier are generally used on CNC machines that have much tighter tolerances and are more rigid allowing for deeper more controlled cuts with feeds and speeds calculated with the surface feet per minute adjusted with the diameter changes. For a home manual lathe you will get better results cheaper with the brazed carbide and high speed steel.
> 
> I really suggest getting the Machinist handbook. It will have any information you may need and then some. Its the bible for machinist and I use mine all the time.


Shaun, I would have to disagree on this whole heartedl, at least in Australia. I have been a machinist for close on 50 years and in the last 15 to 20 years I can count on one hand the number of times I have used HSS at home or in a workshop. In CNC always carbide, in piece work lathes always carbide, on my little TAiG always carbide. You get 6 to 8 hours of cutting from the correct grade and type of tip on 90% of work in a mill, lathe, CNC machine. Consider that you have 3 to 6 minimum tips per insert, that equates to 18 to 48 hrs of cutting per insert. If you buy the best quality at $21 per insert! (Not talking diamond or super inserts) it works out pretty cheap. I have probably used silver steel more often then M2, M35 or M45 HSS. Just my humble opinion. And yes, get a copy of the the Machinist Black book, or download an app. I use FSWizard ( Pro Version) , there are many others.


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## wazrus (Nov 2, 2021)

Depending upon the insert, the cost of replacements can be more than 'a factor', especially for amateurs. Then there are inserts and 'other' inserts. There are very clear quality issues. Insert clamping should also be considered. With my larger lathe, I couldn't find an negative rake insert holder SMALL enough for the centre height and I had to make one. Not a huge issue, but it sure held up the works. If you're OK with paying for inserts, then go for it: as I said, I do use BOTH carbides and HSS and, BOTH have their place. Grinding wheels/grinding machines? Cheap as chips on the 'net and usually come with a couple of wheels. Not necessarily a 'green grit' wheel, but they're not at all pricey, either. Practice is the key: experiment with reliefs and rakes until you arrive at the stock removal/finish you want. Other than some very specialised and expensive insert types, why is it that most drills are made in HSS? And I'm far from being opposed to carbides, but am very aware of the costs and benefits of one vs the other. The 'throw away' bit, for a hobbyist, isn't all that appealing.


----------



## Richard Hed (Nov 2, 2021)

wazrus said:


> Depending upon the insert, the cost of replacements can be more than 'a factor', especially for amateurs. Then there are inserts and 'other' inserts. There are very clear quality issues. Insert clamping should also be considered. With my larger lathe, I couldn't find an negative rake insert holder SMALL enough for the centre height and I had to make one. Not a huge issue, but it sure held up the works. If you're OK with paying for inserts, then go for it: as I said, I do use BOTH carbides and HSS and, BOTH have their place. Grinding wheels/grinding machines? Cheap as chips on the 'net and usually come with a couple of wheels. Not necessarily a 'green grit' wheel, but they're not at all pricey, either. Practice is the key: experiment with reliefs and rakes until you arrive at the stock removal/finish you want. Other than some very specialised and expensive insert types, why is it that most drills are made in HSS? And I'm far from being opposed to carbides, but am very aware of the costs and benefits of one vs the other. The 'throw away' bit, for a hobbyist, isn't all that appealing.


On my small Enco, I broke a lot of carbides, but on the much larger, sturdier Grizzly, I hardly ever break a carbide.  Also, I still use HSS on the Grizz for certain operations, esp. tiny threads which I have made quite a few for small bolts on the Coles/Ray Corliss.  I ruined the half nut on the Enco when cuttin 8TPI which were just too much for that Enco.  The enco just could not go slow enough to cut threads, at least for me.  The slowest speed is 130 rpm.   The Grizz gets down to 70.  For some operations, I wish it was 50.   What a bear (not a Grizzly) to get at the half nut to remake the it.  If Enco were still in biz, I could probably buy one.


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## Bazzer (Nov 3, 2021)

Different cutting tools as much as anything else have their place, I was taught in a formal apprenticeship how to sharpen HSS and I still do this on custom tools but given the choice I go carbide inserts every time.

My lathe is an EMCO 5, I am the only owner from new and it is nicely setup, recently I had a job where PCD inserts were recommended, so I bought one off insert at £30 (approx $42), this insert has taken the lathe into areas of accuracy and capability that I never thought possible, this insert cuts so well that it has for all intents and purposes removed spring back, I am able to wind on 2 micron cuts and see the tiny amount of material being removed - quite incredible.


----------



## Jasonb (Nov 3, 2021)

Richard Hed said:


> The enco just could not go slow enough to cut threads, at least for me.  The slowest speed is 130 rpm.   The Grizz gets down to 70.  For some operations, I wish it was 50.



have you tried threading away from the chuck, speed can be a lot faster as you start from the shoulder and don't have the worry of stopping before you hit it.

The internal threading insert tools are ideal for this as you can easily reach around the back of the part being threaded with the added bonus of correct angles and tip & root radius if you use a full form insert.

Other option is to turn the spindle by hand as many do.

Barrie, I've not had need to try the PCD inserts but I see quite a few of the performance engine makers using them, I assume that piston has quite a bit of Silicon in it.


----------



## Bazzer (Nov 3, 2021)

Hello Jason

Yes the piston is 30% silicon, it is RSA444 material, although the setters were done from regular aluminium 6082 T6 more than likely and this machined equally well with the same characteristics from the lathe, you may notice that the compound slide is canted around at 1 degree to get micron level advances of the tool. 

The finish is phenomenal, I was really surprised the inserts came from APT, they have an online store.

B.


----------



## Steamchick (Nov 3, 2021)

Just looked-up PCD inserts... I didn't understand the jargon... The "D" stands for "Diamond"... but my wife would not wear this one!




__





						PCD Turning Inserts | Cutwel - Lathe Tool Specialist
					

Shop online today for PCD Turning Inserts. Designed for turning high silicon aluminium, carbon fibre, glass fibre and abrasive plastics. UK next day delivery!




					www.cutwel.co.uk
				



This page explains the quality, applications and costs.
You pay your money, and never get more than you pay for...
K2


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## Bazzer (Nov 3, 2021)

DCMT 070202 PCD 1500 Diamond Turning Insert for Aluminium Alloys with >12% Si content Associated Production Tools (shop-apt.co.uk) 

The best improvement I have ever made to any machine tool I have ever owned and all for £30.00 worked the same on 6082 T6 as well.

B.


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## mu38&Bg# (Nov 3, 2021)

Bazzer said:


> The finish is phenomenal, I was really surprised the inserts came from APT, they have an online store.



I'm surprised you get usable pistons with the standard bearings in that spindle.


----------



## Jasonb (Nov 3, 2021)

I might just have to put one on my next APT order, tend to use them for most of the carbide milling cutters for the CNC.


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## Richard Hed (Nov 3, 2021)

Jasonb said:


> have you tried threading away from the chuck, speed can be a lot faster as you start from the shoulder and don't have the worry of stopping before you hit it.
> 
> The internal threading insert tools are ideal for this as you can easily reach around the back of the part being threaded with the added bonus of correct angles and tip & root radius if you use a full form insert.
> 
> ...


On the enco, it would have undone on the spindle if it stuck.  I tried that at an earlier date.  On the Grizz, I could do that but all I have to do is pay close attention to doing it the regular way.  Pluss I don't have the set up for it yet.  I'll get around to it some time


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## Bazzer (Nov 3, 2021)

dieselpilot said:


> I'm surprised you get usable pistons with the standard bearings in that spindle.


Who said they were standard bearings?

No all joking aside, I have changed the bearings but they are only SKF Explorers with a slightly better than normal precision, I think they cost about £28.00 each. The lathe is turning super well, it is difficult to tell the pistons from MB supplied ones.

Ovality in the piston is sub 2 micron and it certainly feels very good in the bore, no cogging as it is rotated and the band forms up perfectly evenly. Malcolm Ross saw a piston cylinder set a couple of weeks ago and he said that is definitely going to run well.

The lathe is well setup and I am very crafty

B.


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## willray (Nov 4, 2021)

Bazzer said:


> Who said they were standard bearings?
> ...
> The lathe is well setup and I am very crafty



You did say the lathe was an Emco, yes?  I would not have expected it to have particularly poor bearings in the first place.


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## Bazzer (Nov 4, 2021)

Agree, but it did have a poor spindle from new, kind of looked like a cam, I bought another off of Ebay which was really nice and changed the bearings at the same time.
Good bearings are very cheap now.
B.


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## mu38&Bg# (Nov 4, 2021)

The Compact 5 uses standard grade deep groove bearings. They are not super precision spindle bearings. This is also the case for some of the small mills. Emco does make premium product, but these were built to a price. Taig and Sherline do the same with bearings, and people do get great parts. The mystical precision required for this specific application is what made me comment.


----------



## Bazzer (Nov 4, 2021)

Maybe you summed it up as mystical precision and with care and good feeling/mechanical sympathy the mystique is smashed !!


----------



## willray (Nov 4, 2021)

Bazzer said:


> Agree, but it did have a poor spindle from new, kind of looked like a cam...



That makes me sad.  Beancounters _are_ the most corrosive force in the universe, and I realize that the smaller Emcos aren't Hardinge Super-Precisions, but it's still disheartening to see a good manufacturer choose to cut corners on quality control.


----------



## Bazzer (Nov 4, 2021)

I think it was one of the last Compact 5's made and was probably done from the parts bin, excepting the spindle issue it is great. I paid £30 for a second hand spindle on Ebay.

The other spindle was fine if you were working down  to 0.00075" (3/4's of a thou) but not finer as I always got foxed by the out of round.


----------



## Bentwings (Nov 4, 2021)

Bazzer said:


> Different cutting tools as much as anything else have their place, I was taught in a formal apprenticeship how to sharpen HSS and I still do this on custom tools but given the choice I go carbide inserts every time.
> 
> My lathe is an EMCO 5, I am the only owner from new and it is nicely setup, recently I had a job where PCD inserts were recommended, so I bought one off insert at £30 (approx $42), this insert has taken the lathe into areas of accuracy and capability that I never thought possible, this insert cuts so well that it has for all intents and purposes removed spring back, I am able to wind on 2 micron cuts and see the tiny amount of material being removed - quite incredible.
> 
> ...


For our small 10” lathe I hone the edges of carbide inserts sharp with a small radius hone on the leadin point this usually gives a pretty good finish however a sharp high speed steel does just about as well . Under microscope carbide is slightly porous or rough. It is a sintered powder so sharp edges break down under heavy cuts .  The chip breakers are there to allow heavier cuts with the chip being s chip rather than a string. I also use some tempered steel shims for lack of a word that are ground and positioned as chip breakers as I don’t like stringy stuff flying around. It takes a little monkeying around to get these to work but once it’s working fine cuts are much easier. I save most carbide for the heavier cuts. Our 10” has a 3 phase motor that’s very powerful so even tough steel like 4140 cuts easily. I suppose one day a gear is going to strip or the lead screw will fail . We have given thought to converting to ball screws but I’m more interested in making a reverse for the lead screw. It a grizzly 602 spin off but has a totally different gear train . Leave it to grizzly yo come up with this system. So far I have not seen another lathe or eve one of grizzly lathes that I could use the gear trains from without a lot of work . If some one has a solution I sure would like to know.
Thanks 
Byron


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## DavidBC (Jul 28, 2022)

I served my time at an Australian company that manufactured sintered carbide tip tools. All the brazed tip tools were finished with diamond wheels with a positive rake and all the sintered tips were left as they were after the sintering process. Considering that they require a small increase in power all carbide inserts that we used were all negative rake as when required you just turned the insert over and you had virtually a new insert, so we got double the use out off a negative rake insert compared to a positive rake. Even though we had a never ending supply of tipped tools to use we still favored the finishing cut to be done with a well ground and honed HSS tool bit on some machined items.

Regards
DavidBC


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## Ozwes007 (Jul 28, 2022)

DavidBC said:


> I served my time at an Australian company that manufactured sintered carbide tip tools. All the brazed tip tools were finished with diamond wheels with a positive rake and all the sintered tips were left as they were after the sintering process. Considering that they require a small increase in power all carbide inserts that we used were all negative rake as when required you just turned the insert over and you had virtually a new insert, so we got double the use out off a negative rake insert compared to a positive rake. Even though we had a never ending supply of tipped tools to use we still favored the finishing cut to be done with a well ground and honed HSS tool bit on some machined items.
> 
> Regards
> DavidBC


In essence carbide doesn’t lend itself to particularly sharp edges, however with todays coatings and superfine structure they do make “sharps”. They are a honed edge tool designed for aluminium or plastic. I have used them for over 10 years now and they are as good as any other for there purpose. I generally work on 6 to 8 hours cutting time for a tip edge. So most carbides are extremely economical to use.


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## Richard Hed (Jul 28, 2022)

Bentwings said:


> For our small 10” lathe I hone the edges of carbide inserts sharp with a small radius hone on the leadin point this usually gives a pretty good finish however a sharp high speed steel does just about as well . Under microscope carbide is slightly porous or rough. It is a sintered powder so sharp edges break down under heavy cuts .  The chip breakers are there to allow heavier cuts with the chip being s chip rather than a string. I also use some tempered steel shims for lack of a word that are ground and positioned as chip breakers as I don’t like stringy stuff flying around. It takes a little monkeying around to get these to work but once it’s working fine cuts are much easier. I save most carbide for the heavier cuts. Our 10” has a 3 phase motor that’s very powerful so even tough steel like 4140 cuts easily. I suppose one day a gear is going to strip or the lead screw will fail . We have given thought to converting to ball screws but I’m more interested in making a reverse for the lead screw. It a grizzly 602 spin off but has a totally different gear train . Leave it to grizzly yo come up with this system. So far I have not seen another lathe or eve one of grizzly lathes that I could use the gear trains from without a lot of work . If some one has a solution I sure would like to know.
> Thanks
> Byron


just exactly what is the prob with the gear train?  What is the center diameter of your gears?  What is the size of the teeth?  Maybe you could send a photo


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## Steamchick (Jul 28, 2022)

Re #63. I have a few odd bits from a plastic machining job, which were supposed to be cutting angles and sharpness for aluminium. I just use them on everything and touch up edges (diamond hone or stone) if cast iron or something takes off the edge.
K2


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## clockworkcheval (Jul 29, 2022)

The slow turning diameter 250 mm wet grinder of Tormek is very good and outrageously expensive. A couple of years ago I could convince the powers to be that one had to be purchased because it is very good at razor-sharp grinding of kitchen knives. The first few times the enclosed band-aids proved to be not a luxury, because we just were not used to handle this sharp equipment. I used it otherwise mostly for larger drills and for wood-working chisels.
Recently Tormek brought out a set of very nice diamond cutting wheels of 250 mm diameter. I found that their Extra Fine diamond cutting wheel with a little water-dip will sharpen to a fine polish both carbide tips and inserts. And the nice thing is that you can also use the huge flat side of the wheel utilizing the standard Tormek tool positioning equipment. Tormek states that with careful use the diamond wheel will last a lifetime. And all of a sudden I use carbide inserts for all regular work, also very fine finishing work. For all special forms I stick with HSS tools. See enclosed pictures.


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## Bentwings (Jul 30, 2022)

clockworkcheval said:


> The slow turning diameter 250 mm wet grinder of Tormek is very good and outrageously expensive. A couple of years ago I could convince the powers to be that one had to be purchased because it is very good at razor-sharp grinding of kitchen knives. The first few times the enclosed band-aids proved to be not a luxury, because we just were not used to handle this sharp equipment. I used it otherwise mostly for larger drills and for wood-working chisels.
> Recently Tormek brought out a set of very nice diamond cutting wheels of 250 mm diameter. I found that their Extra Fine diamond cutting wheel with a little water-dip will sharpen to a fine polish both carbide tips and inserts. And the nice thing is that you can also use the huge flat side of the wheel utilizing the standard Tormek tool positioning equipment. Tormek states that with careful use the diamond wheel will last a lifetime. And all of a sudden I use carbide inserts for all regular work, also very fine finishing work. For all special forms I stick with HSS tools. See enclosed pictures.
> 
> View attachment 138877
> View attachment 138878





DavidBC said:


> I served my time at an Australian company that manufactured sintered carbide tip tools. All the brazed tip tools were finished with diamond wheels with a positive rake and all the sintered tips were left as they were after the sintering process. Considering that they require a small increase in power all carbide inserts that we used were all negative rake as when required you just turned the insert over and you had virtually a new insert, so we got double the use out off a negative rake insert compared to a positive rake. Even though we had a never ending supply of tipped tools to use we still favored the finishing cut to be done with a well ground and honed HSS tool bit on some machined items.
> 
> Regardsinserts usually have some sort of chip breaker built in if you look closely the cutting edge is kinda dull. If you are taking light cuts the tool sorta just pushes a crumpled chip leaving a relatively full surface . The inserts are made to get into the metal . For fine finishes and light cuts I tune the edges and diamond hone to high speed steel sharpness radius the  nose a little carbide is a sintered product so by nature not especially sharp grinding and honing does make very sharp edges but you also sacrifice strength of cutting edge so I you suddenly want a heavier cut you need to go back to  un tuned insert for edge strength. It may cost you one or more sides of the insert but that’s the trade off . A brazed tool is the same way make it razor sharp but it can micro chip and mess up the finish. So you can see why cutting tools are made for the job . HS steel holds the edge longer I think  but you still have to keep it tuned.  It’s possible to grind in chip breakers in HS  but some times you can just add a blocker bar that curly the smaller chip. I’ve don this a lot over the years but it’s often hit or miss.  Grinding in chip breakers can mak the tool a one time use or project specific tool.  Either way costs start entering the picture.
> When youbhavectobfootvthevtool bill yourself you get more choosey
> DavidBC


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## Steamchick (Jul 30, 2022)

Diamonds are forever?
I use a 3in cup diamond "stone"... - replaced a green grit cup stone.tool rest is a few degrees over 90deg. So I naturally grind some relief. Fine for sharpening carbine tips and inserts, for brass n aluminium.
K2


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## Richard Hed (Jul 30, 2022)

Steamchick said:


> Diamonds are forever?
> I use a 3in cup diamond "stone"... - replaced a green grit cup stone.tool rest is a few degrees over 90deg. So I naturally grind some relief. Fine for sharpening carbine tips and inserts, for brass n aluminium.
> K2


When I first got a green stone wheel, I thot it was going to be the stone to end all, use it exclusively for carbide grinding.  However, the stone is so flaky that it grinds away too quickly.  Recently got some diamond embedded grinders which are much better in that way, however is very slow grinding.  When I workt in industry, we had a different kind of grinder, diamond embedded which you put in a mill or drill.  This too was very slow but did excellent work.  Those type are quite expensive:  100USD.  I have been wanting one for years.  Maybe get one this year.


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## Vietti (Jul 30, 2022)

Being cheap I have used diamond discs from China at around $11 ea.  The finer grits work best.  Glue to a substantial steel disc, and away you go.  

Google them

Amazon.com/JOINER-Diamond-Coated-Grinding-Polishing/dp/B01GU3427M/ref=asc_df_B01GU3427M/?tag=hyprod-20&linkCode=df0&hvadid=475864565960&hvpos=&hvnetw=g&hvrand=6923605640146496464&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9029304&hvtargid=pla-1028197055182&th=1


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## Richard Hed (Jul 30, 2022)

Vietti said:


> Being cheap I have used diamond discs from China at around $11 ea.  The finer grits work best.  Glue to a substantial steel disc, and away you go.
> 
> Google them
> 
> Amazon.com/JOINER-Diamond-Coated-Grinding-Polishing/dp/B01GU3427M/ref=asc_df_B01GU3427M/?tag=hyprod-20&linkCode=df0&hvadid=475864565960&hvpos=&hvnetw=g&hvrand=6923605640146496464&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9029304&hvtargid=pla-1028197055182&th=1


Have you tried coarser stuff?  I would thimpfk that coarser would rough grind faster.  doesn't mean I'm right.  What do you grind?  I intend to sharpen carbide bits and carbide end mills (that have broken) into cutting shapes.


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## Steamchick (Jul 31, 2022)

I have a 3" version of this:








						75mm Diamond Grinding Wheel Cup Abrasive Disc For Carbide Metal Cutter Grinder  | eBay
					

Find many great new & used options and get the best deals for 75mm Diamond Grinding Wheel Cup Abrasive Disc For Carbide Metal Cutter Grinder at the best online prices at eBay! Free delivery for many products.



					www.ebay.co.uk
				



Perfectly adequate..? - Replaced the green grit and doesn't wear away. But very slow to remove any quantity of metal, however, I use it for sharpening existing shaped tools, not creating new shapes.
Or this?








						1PCS Diamond Grinding Wheel Sharpener Grinder For Cutter Tool Carbide Metal  | eBay
					

Find many great new & used options and get the best deals for 1PCS Diamond Grinding Wheel Sharpener Grinder For Cutter Tool Carbide Metal at the best online prices at eBay! Free delivery for many products.



					www.ebay.co.uk
				



K2


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## clockworkcheval (Jul 31, 2022)

The only set-back of diamond grinding wheels compared with CBS is, as I understand, that CBS is very heat-resistant but a bit less hard than diamond whereas diamond is very hard but not really heat-resistant. If diamond gets too hot it will crack and pulverize. So a slowly revolving wheel touching water is a good formula for a long live of your diamond grinding wheel. Just putting a diamond wheel on your high-revs bench grinder may be disappointing, but putting a CBS wheel on it works fine. Basically using diamond for finishing and CBS for shaping seems to be the right choice.


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## Vietti (Jul 31, 2022)

Richard,

I find the coarse discs are too coarse for most work and the diamond density isn't very good so the diamonds tend to get knocked off?

I have one of those Leonard grind/laps, 5".  the same machine was sold by other companies with different names.  The factory sells diamond discs but last I looked they were over $160, better quality no doubt.  I bought a bunch of 5" dia,/1/4" thick drops and glued the discs to them.  Need to cut a hole in the center.

I tend to use the diamond discs for all hard materials including carbide.  Tried to sharpen carbide tool inserts-not too good!  Works really nice on cutoff tools.  I never loved the green wheel for a variety of reasons.

John


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## Richard Hed (Jul 31, 2022)

clockworkcheval said:


> The only set-back of diamond grinding wheels compared with CBS is, as I understand, that CBS is very heat-resistant but a bit less hard than diamond whereas diamond is very hard but not really heat-resistant. If diamond gets too hot it will crack and pulverize. So a slowly revolving wheel touching water is a good formula for a long live of your diamond grinding wheel. Just putting a diamond wheel on your high-revs bench grinder may be disappointing, but putting a CBS wheel on it works fine. Basically using diamond for finishing and CBS for shaping seems to be the right choice.


Can you remind me what CBS means?  I thot that was a broadcasting monopoly.


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## Steamchick (Jul 31, 2022)

Cubic boron silicate at a guess? (Whatever that really is!) I must have heard the phrase somewhere....?
K2


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## Richard Hed (Jul 31, 2022)

Steamchick said:


> Cubic boron silicate at a guess? (Whatever that really is!) I must have heard the phrase somewhere....?
> K2


there is a CBN--Cubic Boric Nitride which is used as an abrasive second inhardness to diamond.  But I haven't found any tool bits made of it yet.


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## clockworkcheval (Jul 31, 2022)

My mistake: it is indeed CBN - Cubic Boron Nitride. Hardness only second to diamond. Rpm for a 200 mm CBN wheel 1400 - 3000. The base of the CBN wheel is a steel disc or drum, so no distortion or explosion, and no dressing.
Diamond wheel 200 - 250 mm rpm 90 - 100. The base of the diamond wheel is also a steel disc or drum, so no distortion or explosion, and no dressing.
Both CBN and diamond wheels are expensive, but a one-time investment. They really last extremely long, if well done at least 20 - 30 years. Both should only be used on hard tool materials, not on regular soft steel.


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## davesmith729 (Jul 31, 2022)

Grinding steel on diamond disks can ruin the disks.  Yes, diamonds are the hardest thing but when grinding steel the carbon in the hot diamonds can migrate to the steel and cause many problems which why you should only grind carbide on diamond wheels.


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## ajoeiam (Aug 1, 2022)

Richard Hed said:


> there is a CBN--Cubic Boric Nitride which is used as an abrasive second inhardness to diamond.  But I haven't found any tool bits made of it yet.


Sorry - - - need to look a little further. 
Greenleaf Crop is one name that I remember for such tooling. 
Used on hardened materials and really tough as used (IIRC for the second). 
Didn't use them often but when you drop an insert made of CBN into the lathe and you're turning 4140 - - - - wow - - - feels like race car time!!!!!
(That was the demo in my training.)


----------



## awake (Aug 1, 2022)

davesmith729 said:


> Grinding steel on diamond disks can ruin the disks.  Yes, diamonds are the hardest thing but when grinding steel the carbon in the hot diamonds can migrate to the steel and cause many problems which why you should only grind carbide on diamond wheels.


A very important word of warning. There is a caveat - as I understand it, at least one company sells a diamond grinding setup that 1) runs slowly enough not to build up a lot of heat, and 2) is water-cooled - and as a result they advertise it for use with steel or carbide.

*note that I'm going on the basis of fuzzy memory, so I may not have the details just right ...


----------



## timo_gross (Aug 1, 2022)

Richard Hed said:


> there is a CBN--Cubic Boric Nitride which is used as an abrasive second inhardness to diamond.  But I haven't found any tool bits made of it yet.


CBN wheels can usually be bought from the same companies that also make diamond grinding wheels or other grinding wheels. 
Not as difficult to find as they are difficult to pay for.... haha.
If you want to grind HSS CBN is the way to go.


----------



## SteveM (Aug 2, 2022)

Stefan Gotteswinter is a fine engineer who generally uses carbide for his lathe tooling and has produced some interesting videos on the subject. In one (link below) he regrinds carbide inserts, producing a sharp edge and demonstrating that the results in cutting steel, brass and aluminium are outstanding. In another he brazes used carbide endmills onto cold rolled steel for use on his small lathe.

Here's the one about the inserts:   Regrinding Carbide Inserts


----------



## Nerd1000 (Aug 2, 2022)

ajoeiam said:


> Sorry - - - need to look a little further.
> Greenleaf Crop is one name that I remember for such tooling.
> Used on hardened materials and really tough as used (IIRC for the second).
> Didn't use them often but when you drop an insert made of CBN into the lathe and you're turning 4140 - - - - wow - - - feels like race car time!!!!!
> (That was the demo in my training.)


You can pick up Chinese CBN tipped inserts on eBay. One insert will cost you the price of an entire box of carbide tips, but on the other hand it's possible to turn heat treated HSS with them.


----------



## william_b_noble (Oct 9, 2022)

what I will add to the carbide discussion is I have what is a "small not rigid" lathe by industrial standards, but it weighs about 1200 pounds and is massive by the standards of these little lathes you can lift with one arm.  I use carbide a lot, it will cut though mill scale and surface hardning where HSS won't, I can run it making beautiful bright blue chips - and I  can get a glass like finish with the right materials.  But carbide is supremely brittle - I don't think I've ever worn out a carbide tip but many have failed with a broken tip - if the material is softer or you aren't taking massive cuts, then I think the recommendation to stick with HSS mostly is a good one.


----------



## Bentwings (Oct 9, 2022)

william_b_noble said:


> there is nothing wrong with using carbide as long as you understand how they work. You can hone them to a razor sharp edge and they will cut nice but as soon as that edge chips even slightly  everything can go down the drain in a hurry . There are some incredibly tough HSS tools that don’t dull easily and if you make proper chip breakers they cut nice and clean  you can even get stringy materials the chip nice.  We probably have several hundred dollars of broken carbide tools in the lathe cutter box   I have a few really high quality HSS tools that are my own carefully stashed.   I don’t see well or hear well and I’m not supposed to even be in the shop  but I still sneak in for that special thing I need made  the little lathe can’t handle heavy cutting on alloy steel like 4130 or 4150  the same with the small mill it’s not a series 2 Bridgeport or big Cincinnati   .   But I still can bore a hole to a pretty exact size  using the right tools   I don’t make much out of hot rolled anymore I don’t even like welding it
> 
> So each to their own. What ever works for you is good.
> what I will add to the carbide discussion is I have what is a "small not rigid" lathe by industrial standards, but it weighs about 1200 pounds and is massive by the standards of these little lathes you can lift with one arm.  I use carbide a lot, it will cut though mill scale and surface hardning where HSS won't, I can run it making beautiful bright blue chips - and I  can get a glass like finish with the right materials.  But carbide is supremely brittle - I don't think I've ever worn out a carbide tip but many have failed with a broken tip - if the material is softer or you aren't taking massive cuts, then I think the recommendation to stick with HSS mostly is a good one.


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