Are lathe tool carbide inserts supposed to be sharp?

[ChazzC]

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

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

 

[Makerphil]

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.

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.

 

[Mechanicboy]

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..

 

[Richard Hed]

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.

 

[Zeb]

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.

 

[Makerphil]

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.

 

[Richard Hed]

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.

 

[Jasonb]

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.

 

[GrahamJTaylor49]

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.

 

[ajoeiam]

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.)

 

[Ozwes007]

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.

 

[Makerphil]

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.)

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

 

[minh-thanh]

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 :

 

[Mechanicboy]

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.

 

[awake]

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.

 

[SmithDoor]

I agree

Dave

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 :

 

[wazrus]

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!!

 

[Makerphil]

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.

 

[Bazzer]

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

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!

 

[Makerphil]

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!

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.