Face Mills And Inserts

[65Cobra427SC]

I have a project pending that involves using my PM932 to cut a taper on one side of 4" wide 8" long x 1/4" thick sections of stainless steel. Up until now I've used fly cutters and individual end mills for this type of thing but I'm not sure I should use them for these larger pieces.

I've been reading about the various types of face mills, degree of cutting, odd vs even cutters, types and costs of inserts, etc. and felt it would be a good idea to purchase 2 or 3 indexible face mills. Since I only know the basics at this point, trying to make a decision on my own is difficult, especially since I'm trying to do this during Shars black friday sale.

I was hoping others could chime in with specifics on which types and sizes you found more useful over the years. Heck, feel free to visit Shar's website and do my shopping for me

Thanks

 

[Bob Korves]

Fly cutters will do nice work out to really big diameters, but with slow metal removal rates at those sizes, the depth of cut must be quite shallow when cutting big areas. For removing more metal, a face mill is the choice, though usually much more expensive, and sometimes you have to work at getting a nice finish when using one. They also require more horsepower and rigidity in the mill as more inserts do the work. I do not own a face mill, and have not missed it so far...

 

[T Bredehoft]

I once used a face mill 9" in diameter with 26 Sandvic Cormorant inserts, working cast iron. It was really sweet. I could do the side of a crank case 24 inches high in three passes. It was on loan, and once someone used it on steel, management wouldn't buy more inserts, so we lost it.
Working a 4" by 8" piece, to thin one side on a taper, hmm. grind it? You can't hold it well enough to face mill it. As you cut it would bow toward the cutter from heat and side pressure. Or are you tapering the edge?

 

[65Cobra427SC]

Bob, I'll at least try the fly cutters and see how they do, but would still like to get at least one face mill, mostly as a just in case. But I'll eventually need one and black friday seems to be a good time to make the purchase.

Tom. A neighbor sometimes runs lathes at work and says mine are like toys The plates are 8" long but the taper will run across the 4" width so I'll be able to taper half a plate at a time while the other half is in the vice... plus I will take my time and remove as little metal as possible at a time. Also, the taper only needs to go from 1/4" (no taper) to 1/8" so essentially, it's only a 1/8" difference within the 4" span.

Actually, it just occurred to me most of the plate will be hidden so I could actually drill holes in the plate and bolt it down during the cutting process.

 

[T Bredehoft]

A neighbor sometimes runs lathes at work and says mine are like toys

Yeah, the largest pieces I've turned (at work) were about 32" diameter, we had to put a 24" O ring groove in them, test flanges for pressure testing cylinders. My 6 by 20 MK2 really is a toy. but it will cut steel, and hold dimensions.

 

[petertha]

I have an RF-45 type mill & bought a 2" dia facemill that looks like this, uses 4 APKK inserts. I could not be happier with the finish on steel & especially aluminum with non-coated slightly higher radius inserts. It exceeds anything I ever did with fly cutters. But will take deeper cuts. I will lop off 20-thou & not think twice. I'm sure this can be pushed but basically I use it for facing. I have not used my flycutters since & probably never will. My logic was 2" was about right, going to a much larger diameter facemill head just means more inserts & more hp. There is nothing wrong with making a few passes traversing a wider part. Trying to flycut say a 6" wide swath in one pass sounds like 'a plan' & the finish may look uniform, but in reality it has downsides IMO. The allowable depth of cut is typically small & feed rate is very slow & reduced rpm because of high radius (SFM). Also I think it magnifies even a minute misalignment between quill axis & work translating into potential for scallop cut. I'm not suggesting traversing a smaller cutter solves these setup problems, but this seems to be a happy medium for me on this machine. One cutter, set of inserts for steel & aluminum, done.

I cant tell you if the Asian knockoffs are good. I believe mine came from Tawian & its very accurate & runs smooth. The inserts are getting very inexpensive on ebay/Ali. Also after the fact Ive seen heads that use the 'other' corners of inserts. I guess you'd have to weigh the cost/return there. Good luck!

 

[65Cobra427SC]

petertha, good info... thanks! It's on my list.