carbide wear

[Rich L]

I just got through turning a bunch of rectangular 1.5 foot acrylic blanks into round blanks using a carbide insert tool. This is a rare occurrence! I estimated that the lathe went round about 230,000 times turning this roughly 5/8 stock. I thought, for fun, I'd take a picture of the insert to see if there was any appreciable wear and ask if others have found the same or similar result. This insert has been used before on some metal cutting - steel and brass so there is some initial wear. The insert type is TNMG221 with a 1/4" inscribed circle. The corner radius is 1/64". It boiled down to about 4.5 hours of constant turning and I see nothing significant to report from the acrylic.

If this is a yawner, I apologize. I think a lot of you use HSS tooling but mine are all either indexable or solid carbide. Do you find that your carbide lasts forever in this stuff? I would not expect much wear but just checking.

Cheers,
Rich

 

[randyrls]

Rich; I use flat topped inserts and when they become dull I just sharpen them with a diamond hone. Work like new. I don't have to sharpen too often, about 5-10 pens depending on the material. Some of the Trustones are hard on cutters.

 

[Rich L]

Rich; I use flat topped inserts and when they become dull I just sharpen them with a diamond hone. Work like new. I don't have to sharpen too often, about 5-10 pens depending on the material. Some of the Trustones are hard on cutters.

Thanks, Randy. That's a great idea for touching up both the inserts with chip-breakers and flat-topped ones. I'll have to do that. I'll probably even try touching up the relief, too.

Cheers,
Rich

 

[Dalecamino]

Yes, I like them really well.

 

[robutacion]

There are far too many types on materials used on these inserts and some are a lot better than others. So far, any of the inserts that I purchased from well know quality blanks, have proven a better investment than many that are now appearing on the market made in China.

Quality brand ones are more expensive to buy but, they are a better investment in the end, for many reasons and while carbide inserts can be re-sharpen, a top quality insert will never need re-sharpening. They are made to brake the edge when its cutting edge has reached in life expectancy, as nothing re-sharps them, I know I tried with quality diamond tools...!

Carbide tipped inserts are no doubt, one of the best inventions man as created...!:wink:

Cheers
George

 

[Rich L]

Did some on-line research and found that regrinding carbide and ceramic inserts is not uncommon. If they are coated, they can be recoated and some shops offer cobalt enrichment. The downsides mentioned are keeping them separate from ones of original size since both the thickness and the inscribed circle will decrease (from grinding the relief sides); the fuss of packaging used inserts up and sending them off to the regrinder; and tool offset resetting for CNC machines.

There's always the cost/benefit analysis about whether or not to regrind or buy new but I saw no technical materials-based reason behind not to regrind other than not grinding away the chipbreaker. A severely chipped, spalled, cratered, or thermally cracked insert is trash but one with just a worn edge (abrasive flank wear) or light chipping can be reground. Even the best stuff will wear.

Of course, cheap stuff will still perform like cheap stuff.

Here are a few shops that do it. That's not evidence in itself that it's a good way to go but the professional discussion forums (fora?) don't discount it. Some of the proof for me will be in my pudding.

Regrinding Inserts & Downsizing Inserts provides efficient carbide insert recycling for standard & specialty tooling.
performance carbide regrinding inserts downsize
Madill Carbide, reground insert, reground inserts,regrind insert,Carbide resizing, Carbide regrinding, Sharpening in Wichita, Kansas
... you'll find more

I just never thought of it so I''ll put the diamond lapper to some additional use. Probably just take the insert and take just a thou or two off and then take some diamond lapping film to round off (hone) the edge. I don't want it sharp.

IMHO inserts are the cat's meow!

Cheers,
Rich