Aluminum Chip Welding..?

EmilioG

EmilioG

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First time I've had this problem. I was boring a few large holes, 1-2" in 1/2" thk. 6061. I noticed after, that I had a few light, small specks on the boring bars tip.
The work was done on an old BP mill using a Criterion Boring head with carbide and cobalt boring bars, running at about 325 RPM. I used Relton A-9 cutting fluid.
I suspect that my speeds and feeds have something to do with this problem. Also, is there a good way to get these tiny chip welds off the tools? They're are more like flat smears. Advice needed. Thanks
 
I've read this as a first line of attack. Hope it works with a boring bar. I'll try it on a piece of mild steel tube.
 
Use uncoated carbide and higher speeds for aluminum.
 
Yep, I mostly use un coated tools for aluminum. Never had a problem with coated tools either, so I will look at the speeds.
Both boring bars were un coated, carbide and cobalt bright. Higher speed may be the solution. The finish was poor also.
Smooth but with striations, almost like wood grain. The old BP mill isn't helping either. Needs work.
Side note: I like old iron, but very expensive to refurbish many old USA made machines....cue the music..! Violins with lot's of pathos.
 
Maybe try snugging up the gibbs a bit, lock all unused axises and make sure everything is tight on the boring head, etc.
 
Tap Magic for Alum? Never had a problem, but the speeds/feeds sharpness and aluminum may all play into it. So it's hard to say.
 
Also consider using HSS tools for aluminum, especially if you want a very nice finish.
 
Check. Did all those things. I think it may be speed. I'll try higher speeds, especially on the carbide tool.
I've always had better luck using carbide tools at higher speeds. I did switch over to HSS cobalt, but got the same welding/smear/sticking.
The particles are very small. At first, I though they were chipped, but under magnification, they are welded smears, very flat.
 
Rather than increase speed, may I suggest you increase feed and see how that works. Boring bars work better at higher feed rates than you might expect.

Trying to knock off a BUE is a crap shoot. Sometimes you can knock it off but most of the time you will chip the underlying tool material. On a solid carbide or cobalt bar, I would use a diamond stone and hone it off.
 
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