at work we are making about 100 1in dia 6in long 12pt screws for military application out of inconel 718. they are forged and then machined. we are using tungaloy TNMG 432 AH120 (inconel grade) inserts. i am facing .083 off of the head height and chamfering. i am using a g71 roughing cycle. i am running these on a haas tl1 with coolant. i asked my boss if he had used ceramic inserts before and he said he had but that they wouldn't work because it is an interrupted cut. need feeds and speeds and depth of cut. tried every thing from 250sfm to 90sfm, .0035f to .006f, and .010doc to .025doc. my inserts are lasting 1 to 1.5 parts and are screaming. i also have to cut .030 off the other end so they will be in tolerance. HELP.

bookwurm99

P.S. btw 1k$ per part.

It's just about right.... Inconnel will eat your insert like crazy, so buy more insert for the job.

Look into greenleaf carbide reinforced ceramics. There is an article in Modern Machine Shop that dealt with ceramics and interupted cuts. Instead of slowing down, you gotta speed it up. Because ceramics work by melting the material and moving it away. with an interupted cut, the material never has a chance to heat up, unless you increase your surface speed.

Try filling it with wax. We use a product called Rigidax here for machining impeller contours. it really helps to soften the blow of the interruption It won't make the material any softer but it may get you some better tool life.

:cheers:

Try filling it with wax.
cdlenterprises:take a look at a 12pt socket wrench. the id is the shape of the head. i don't think the wax idea will work on that shape.

. There is an article in Modern Machine Shop that dealt with ceramics and interupted cuts.
big mac: any idea on the time frame of that article? would make it easier to find.

cdlenterprises:take a look at a 12pt socket wrench. the id is the shape of the head. i don't think the wax idea will work on that shape.

Than I guess it won't work. Sorry to bother you, pal.

http://www.mmsonline.com/articles/049903.html

Here is the link to the article online!!!!!

Cheers

Another thing to try is to use a button shaped insert for as much as you can, and take out any corners with a pointed insert after!!!!