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Thread: Lathe carbide tool geometry
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1st Sep 2021, 10:45 AM #76Most Valued Member
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Something is definitely not right if you are getting sparks when rough machining castings, you will need to change your current machining parameters, shouldn't get sparks with cast iron on those types of lathes.
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1st Sep 2021, 02:09 PM #77Diamond Member
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Cast iron, and probably too fast. I can't remember if it was the top surface (which might have had slag, but should have been ground off), or was the sand moulded surface (which might still have some sand in it?).
Either way, was probably blunt tool. (I would never start with a sharp one on something rough )
That, and the negative geometry, is just pushing material into a little hot spot
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1st Sep 2021, 07:52 PM #78Diamond Member
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Those inserts you bought are probably counterfeit, it happens a lot from china. We buy very similar inserts from Sumitomo and they are $18-22 each insert.
The hardness of the toolsteel you machined with the WNMG wouldn't have changed, all the heat of the cut should have been transferred into the chip not the part, same concept as hard milling. the harder grades of carbide (P10) will turn up to 45Hrc pretty well, i have gone up to 50Hrc put tool life is pretty poor.
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1st Sep 2021, 08:30 PM #79Diamond Member
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If the price is too good to be true ...
Yes, I expect they are not real Mitsubishi,
although the company does have some non-domestic carbide plants:
Manufacturing Plants | MITSUBISHI MATERIALS CORPORATION
(TianJin China, Taipei Taiwan, Ayutthaya Thailand, java barat Indonesia, Maharashtra India)
so you never know what falls off the back of a truck,
or gets raided from the reject bin,
and sold on AliExpress etc.
TNGG with nice positive top rake will be an improvement on what I currently use, even if they are not actually ground.
Remains to be seen if they are actually ceramic. I'm guessing Cermet.
As an aside, the last two boxes of threading inserts I got;
https://www.aliexpress.com/item/4000297806132.html
https://www.aliexpress.com/item/4000305516087.html
were meant to be generic, but were actually shipped with Mitsubishi stickers, and have been really good.
I think the second set was even a beautifully moulded chip breaker - like the first - instead of the flat rake in the picture.
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1st Sep 2021, 10:20 PM #80Diamond Member
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They wont be ceramic, ceramic inserts are only for hard turning and cant have a positive rake. They will be cermet and they will be ground. I have tried a couple of knock off inserts, they are generally, dimensionaly good, but the quality of the carbide and coating is sub standard.
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