Carbide inserts

[Gordon]

I have a lathe tool holder which came with TCMT32.51 yellow inserts. Amazon offers these as well as TCMT32.52 Brozen. Not sure what Brozen is but as I read it the 2 at then end is the tip radius. 1=1/64 radius and 2=1/32 radius. Would the larger radius give a smoother cut? My problem with breakage is when facing if the cutter is just slightly above center it tries to jump under the nib it breaks the tip off. Not sure if a larger radius would help that. I know that many of you will tell me that I should buy from better sources but so far I have been happy with the results for the last 2 or 3 years and $2/piece against $20/piece does not seem to be worth it. I am building model engines, not parts for the space station.

Thanks

 

[mu38&Bg#]

Inserts are fairly complicated and there is tremendous selection in edge geometry. Increased tip radius theoretically gives better surface finish for a given feed rate, at a cost of increased tool pressure. This means you need a rigid machine. If you're already pulling the tool under the work, I doubt larger radius will help.

Links to the actual tools in question could be helpful depending on how much detail they offer. I have to say though, that I've never purchased no-name or fake inserts as there is no telling what you're actually getting.

With all that said, is there a reason the center height is not checked? Some of this comes down to technique and machine capability. Is there a reason you don't face with 80° rhombic inserts? How deep is a facing cut?

 

[Gordon]

The problem with being off center is that there is enough spring in the machine that it is forced below center. I am taking about .015" per cut. The lathe is a 13" South Bend of 1940's vintage so it is fairly robust but was never a high precision machine and has had quite a bit of use. This is a hobby and I am 82 years old so I have no intention of doing a lot of upgrading. I probably could afford to spend more for machines and tooling but it just is not worth it to me. I can purchase 10 inserts for $20 or spend $20 each. Like I said there is a limit to something which is just a hobby. The reason that I am using those inserts is because that is what the holder that I have will accept. I think that I will probably just buy 10 inserts with the larger radius and see what happens. I will only be out $20 for 10 inserts.

 

[Vietti]

Gordon, The price of inserts bothers me too. I've been completely satisfied with the quality and price of carbide inserts from Bangood. Tooling is good too.

John

 

[Richard Hed]

The problem with being off center is that there is enough spring in the machine that it is forced below center. I am taking about .015" per cut. The lathe is a 13" South Bend of 1940's vintage so it is fairly robust but was never a high precision machine and has had quite a bit of use. This is a hobby and I am 82 years old so I have no intention of doing a lot of upgrading. I probably could afford to spend more for machines and tooling but it just is not worth it to me. I can purchase 10 inserts for $20 or spend $20 each. Like I said there is a limit to something which is just a hobby. The reason that I am using those inserts is because that is what the holder that I have will accept. I think that I will probably just buy 10 inserts with the larger radius and see what happens. I will only be out $20 for 10 inserts.

What kind of tool holder do you have? I ussed to have a SB 1918 model with a rocker style tool holder. I used it a few years till I discovered the Square tool holder. Used that for a while but kikt and kurst it. finally I managed to get a QCTP with a few extra QCs. Stopt the kursing and my toes healed.

Point is, those rockers are notorious for flopping about and getting out of center.

 

[animal12]

Bottom of this link has a chart on inserts that may be of some help . Those folks also sell HSS inserts that will fit your tool holder . I've been using them for years with no complaints .
https://www.arwarnerco.com/category-s/142.htmanimal

 

[johnmcc69]

Theres always HSS blanks.
Get a good grind on them, learned that in trade school. Watch your speed & feed.
Carbide seems to work on the higher HP production machines, flooded with coolant. Hobby machines may have a problem pushing carbide, Needs a lighter chip load.

What kind of material are you trying to cut?

 

[ajoeiam]

I'm wondering if your tool nose breakage is because your tool is off center.

I was taught to find the center height but using a short rule (any piece of thin STRAIGHT material will do).

1. move the slide up to the work placing the rule between the tip of the tool and the work
found that having the rule about half up and half down worked well
2. move the tool to where the tip of the tool touches the rule which then touches the work
careful - - - use just enough pressure to hold the rule - - - - no more or you break the tip whilst trying to figure out why the tip is breaking!
3. look at the rule carefully (!!!!!!!!!!!!)
is the rule vertical??
4. adjust your tool height (back off the work first (catch the rule too))
if the top of the rule is further to the work you're too high
if the top of the rule is away from the work you're too low
don't adjust much - - big movements are NOT your friend
5. check using the rule

A simple method that is doable in a very short time with almost nothing for equipment. (I didn't even use a rule - - - just needs to be something straight)

If your tool tips continue to break off then you likely have too much flexure in your tool holding system.
That will cost you some $$$.

Had occasion to use really cheap inserts - - - - thought that they were a false economy.
Found that buying at least good quality tooling paid dividends (in a lot of ways).

From an unrelated enterprise (logic is similar - - - feeding livestock) "You can't starve in a profit!".

 

[stanstocker]

I have a lathe tool holder which came with TCMT32.51 yellow inserts. Amazon offers these as well as TCMT32.52 Brozen. Not sure what Brozen is but as I read it the 2 at then end is the tip radius. 1=1/64 radius and 2=1/32 radius. Would the larger radius give a smoother cut? My problem with breakage is when facing if the cutter is just slightly above center it tries to jump under the nib it breaks the tip off. Not sure if a larger radius would help that. I know that many of you will tell me that I should buy from better sources but so far I have been happy with the results for the last 2 or 3 years and $2/piece against $20/piece does not seem to be worth it. I am building model engines, not parts for the space station.

Thanks

To answer your specific question, odds are a 322 or 32.52 insert has enough radius to give a good finish. One heads up is that a 32.52 is just a wee bit thicker than a 322, so interchanging them can lead to thinking your tool tip height is good while it is in fact slightly high.

If you mount a nicely ground HSS cutter in the same tool holder, at the correct height, does the problem go away? If so, blame the cheap carbide insert or the tool holder. Otherwise read on and hopefully something will apply...

If the cutter is jumping under the nib I'd suggest getting the tool height dialed in. Minimize overhang of the tool, the more rigid the entire setup the happier the world becomes. You might check for any play or flex in the tool post and compound as well, certain machines like the ubiquitous Chinese sourced 9X20 lathes are notorious for the compound mount flexing. Try to avoid advancing the compound any further than required. The goal is to have a close to a straight line from the cutting tip down through machine rather than air to the carriage, and to have that line within the lathe bed.

I've seen folks with two inches of tool out in the breeze, compound advanced way out in space, machine chattering away no matter what oil or speed / feed they try. Pulling the tool in close to the tool post and the compound back so the tool post is centered over the compound base can work wonders in these cases.

One spot often overlooked is the surface quality of the insert pocket in the tool holder. It must be flat, and the insert should nicely fit. Sometimes a very brief bit of work with a stone will show easily removed high spots. If not flat, the insert can rock or vibrate even with the screw or holding clamp tight. Broken insert to follow.

You might try buying just a couple of name brand inserts once the above is done. Good carbide does cut better and tends to last quite a bit longer. At least you will then know rather than wonder if the lower cost inserts are OK or the source of your problems. Not all cheap carbide is swill, and not all expensive carbide is glorious, but most of the no name import carbide I've seen has been variable in quality. I threw out the 221 "carbide like" inserts that came with some 1/4 inch tool holders from a name brand retailer, while some of Travers house branded stuff years ago was excellent Kyocera made stuff.

Too much material projecting from the chuck or a loose spindle in the head stock can also allow the work to flex and ride up over the insert as you approach center. Work riding up or cutter diving down tends to give the same sort of bad results.

Best of luck with it,
Stan

 

[Steamchick]

I assume the gib strips are correctly taken up to minimise slack / chatter in the slides and carraige? On worn old machines I was taught to tweak to "right, at the cutting position". Even if the slides went tight at the less worn ends of travel.
K2

 

[Steamchick]

BROZEN is a brand name for Boron Nitride... the common stuff used to make Carbide inserts. I think?
Another point. These inserts tend to be blunt. Because they work on high contact pressure. Small and old, worn lathes (my life!) cannot always develop the pressure of contact for carbide tip geometry, simply because the small or worn parts are not stiff enough. A good cause of tool "diving under"! Big industrial strength machines are very stiff, and can take the machining forces without distorting.
Sharp HSS tools will solve the problems, or did for me. Now I have a diamond hone to sharpen inserts and they work fine as well, when often new inserts are not happy.
Have fun experimenting.
K2

 

[RM-MN]

BROZEN is a brand name for Boron Nitride... the common stuff used to make Carbide inserts. I think?
Another point. These inserts tend to be blunt. Because they work on high contact pressure. Small and old, worn lathes (my life!) cannot always develop the pressure of contact for carbide tip geometry, simply because the small or worn parts are not stiff enough. A good cause of tool "diving under"! Big industrial strength machines are very stiff, and can take the machining forces without distorting.
Sharp HSS tools will solve the problems, or did for me. Now I have a diamond hone to sharpen inserts and they work fine as well, when often new inserts are not happy.
Have fun experimenting.
K2

Boron nitride is a special case of carbides used for its superior hardness but a carbide is defined as a metal and carbon like iron carbide or tungsten carbide. The advantages to these is their hardness which makes them wear longer but the tradeoff is that being that hard makes them brittle and easy to chip. In industry the carbide isn't necessary to be so sharp as the machines are large and have sufficient horsepower to keep working and making big chips. With home shop machines these carbides are a bad choice....except that there are inserts that are made sharper for cutting aluminum. These cut steel very well at the reduced depth of cut that the lower power home shop machines normally have. HSS isn't as hard so it isn't so brittle and can have a very sharp edge but it wears quicker and needs to be resharpened. Not every home shop machinist can reliably make them sharp enough so a carbide insert tool makes a very good substitute as they will come at the appropriate shape and will be appropriately sharpened.

 

[Steamchick]

Aha! I have some "aluminium" inserts, and have used them on steel successfully. I didn't know why they were so good! I do prefer them to "steel" inserts, except for cast or sintered iron or steel materials, that can be horribly abrasive with the wrong speed/cut/feed. Thanks for the correction as my knowledge was innadequate (as usual?).
K2

 

[mu38&Bg#]

Are we assuming all carbide inserts have negative rake? There is a large selection of positive carbide tooling available. You just have to study the catalogs, if available. Brand name tools with specs are available and do maintain a level of quality.

Anyone actually look at catalogs for edge geometry and edge prep? Or is everyone hoping they get something useful for 2$/insert?

Brozen turns up exactly nowhere on google. Cubic Boron Nitride? That's CBN used for cutting hardened steels. Common, but not in 2$ inserts. Brozen is actually a typo on the amazon listing for bronze, which is used to describe the color of the insert, which is somehow important.

Is everything a guessing game?

Regardless, it's quite obvious OP wasn't looking for input or discussion, but confirmation of the decision he already made. But it's just a hobby so flushing a 20$ down the toilet is a good a time as any.

 

[L98fiero]

Brozen turns up exactly nowhere on google. Cubic Boron Nitride? That's CBN used for cutting hardened steels. Common, but not in 2$ inserts. Brozen is actually a typo on the amazon listing for bronze, which is used to describe the color of the insert, which is somehow important.

Borazon however is the trade name General Electric gave to cubic boron nitride (CBN) when they first produced it in 1957

 

[Apostle]

Unless your job calls for carbide tooling, due to speed of completion, hardness, etc., why not just use good old tool steel shaped according to basic principles? Tool steel cuts great and leaves a wonderful finish on most materials. Just my 2 cents worth. Best, Mike DiGirolamo, Charlottesville, VA

 

[Shopgeezer]

I have to admit that despite my original preference for tool steel my current carbide cutters work so well my tool steel collection is gathering dust. I did put some serious money into the carbides. The only tool steel I use now on occasion is the diamond tool holder from Eccentric Engineering. It does a great job and the tool is very easy to sharpen. Using a round cutter in that tool holder produces a mirror finish in brass.

 

[Gordon]

I have to admit that despite my original preference for tool steel my current carbide cutters work so well my tool steel collection is gathering dust. I did put some serious money into the carbides. The only tool steel I use now on occasion is the diamond tool holder from Eccentric Engineering. It does a great job and the tool is very easy to sharpen. Using a round cutter in that tool holder produces a mirror finish in brass.

A couple of thoughts: I also have been very satisfier with the carbide cutter that I have been using almost exclusively for the last few years. I can get a HS tool to cut and cut well but it gets dull much sooner than the carbide. Once you remove a HS tool to resharpen you have to compensate for the amount ground off. In spite of all of the remarks about carbide only working with deep cuts and heavy feed that has not been my experience. I just was looking at Blondihack's You Tube channel and she also is using carbide and her equipment is lighter than mine. If it works don't fight it. One thing that I did learn is someone suggested that they use a diamond file to resharpen and I tried that and it does help. Obviously for special shapes etc. HS is the only way to go. For the most part the problems that I have had with the carbide cutters has been because of something that I did wrong. I have used the same carbide insert for extended periods of time and even the cheap ones can last a long time.