jeff

Finish turning Inconel 718 40-44Rc

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We have a couple of parts where we have to finish an interrupted face in the lathe. 

We have carbide and CBN and the face has a tight tolerance on flatness, location and some other stupid callout.

The interruptions keep chipping the cbn,and the carbide pushes off .001" when it hits the holes.

Have tried cbn at 150-350 sfpm, and carbide at 50sfpm.

Any suggestions will be appreciated.

Parts are about 6" dia 1" long.

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Best inserts I've run on that evil material were the Walter inserts, I cant tell you which ones though, long time ago and about 4 jobs ago.

Can you drill the holes after the facing?

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3 minutes ago, AMCNitro said:

Best inserts I've run on that evil material were the Walter inserts, I cant tell you which ones though, long time ago and about 4 jobs ago.

Can you drill the holes after the facing?

The holes are already in the part. 

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Our Sandvik rep just happened to be on his way over and solved the issue. Was it a perfect fix? No, but we just used a grade 1150? 1105? cnmg 200 sfpm .006 ipr. 

The deflection from the holes is now at the high limit of .0003" so we're calling it good.

This material sucks balls.

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Jeff,

I like the Walter inserts also, been using them for quite a few years on 718 and Vanadis 4 materials. Initially had issues with coolants being on the lean side, this causing heat and then catastrophic insert failure .

Depending on the nose rad you can use, I typically stick with the CNMG120408-MM5 WSM10S series. The 10s is pretty tough carbide.

Found down cutting the faces w/in .0005 and then finish turn the entire profile to size seems to keep the faces w/in tolerance.

SFM was right around 60/70ish. Depending on your D.O.C, FRates around .0075...

Part quantity was alway low numbers (4-6), so i'm unsure how any long any insert would do in long run cases.

From some of your prev posts, I'm sure you've about tried all variations of Feed/speeds.

Hopefully that can help.

Rob

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I've had similar situations to this.  Is there any way you can mill the face?  That has worked for me a few times where the appearance didn't matter.  Milling seems to take the interruption better.  This is one of those sucky situations.  I also have had good luck with Iscar CNMX:

https://www.iscar.com/eCatalog/Family.aspx?fnum=1292&mapp=IS&app=0

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Sandvik has new CBN grades, specifically for interrupted cutting. I just watched a video on LinkedIn yesterday that demonstrated cutting gears with the interruptions of the teeth. Grades 7125 and 7135 designed for interrupted cutting.

 

 

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