Peel mill in narrow slot

[Bob W.]

I have a production part with a narrow slot that is .5" wide x .8" deep and 10" long.  I have been milling this with a contour toolpath and a 3/8" end mill.  The material is 4140 steel at RC45 and my customer has decided they want these to be machined at RC52-54.  I would like to machine these with a peel mill toolpath but I have heard in the past that this can be hard on ball screws because the rotation isn't enough to allow them to get proper lubrication and it accelerates wear.  Any thoughts on this?  I think a 1/4" end mill with a 5% step and /4" DOC would work great but not if it wears out my ball screws.  I typically machine these parts in batches of 50.

[GoetzInd]

Bob,

   Can you position the part at an angle so the screw isn't just going back and fourth in the same spot? Also, maybe high feed with 12mm indexable. 

 

Mike

[Bob W.]

I can't skew the part because it is a 4-axis part and there are features at 90 and -90 degrees.  I could use a high feed cutter but insert life in the hard material would be an issue I believe.  Also, I would need to buy four of them so I could run them on both machines and change inserts without stopping the machine.  I'll look into it but I really don't like indexable cutters that much.  I haven't had that much luck with them in the past and one oops where an insert fails and the holder is scrapped...

[Robert Ouellette]

what about solid carbide feed mills? I have had really good results with the Kennametal feed mills. in the harder materials they last a long time. in softer stuff not so much.

[Chris Rizzo]

I wouldn't think you'd be able to beat peel mill performance, here is a link to the old topic and the mori that had problems

 

 

2009 thread on Mori smoked bearings

Also false brinelling.

 

Mayye Makino could  do some calculations if your ossilation distance would be enough for a ballscrew bearing to circulate. Tell them you'll make a video on how bad-xxxx it will be

[Bob W.]

Thanks for the link Chris.  After re-reading that (I read when it was first posted) it sounds like .25" movement wouldn't be an issue.  I remember the slots were small but .007" movement it pretty crazy...  I'll give it a shot with the 1/4" tool.  I'm thinking 10k rpm and 100 ipm @ .4" DOC?

[Chris Rizzo]

No problem Bob. I'll bet you'll be able to crank up that feed a bit. I recall running an uncoated garr 1/4"  .500" loc at about those speeds in A2. I believe about 8-10% stepover.

 

hth!