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Internal chamfer

madmachinst

Stainless
Joined
Jan 15, 2007
Location
Central FL
I got to make an internal chamfer. the bore goes from .559 to .314 and the chamfer is 92 degrees included angle. Anybody got an ideas. I was thinking about picking up a jobber drill at the scrap yard and regrinding it, but I have bad experience running form tools. they tend to squeel and whine a lot.
 
If it's not too deep, and it's a lathe job, you could swing the compound to 46 degrees and use a conventional single-point boring tool

If you have to do it with a re-ground drill, first use conventional drills to take as much meat out as you can. Then take a piece of tough rag (denim's quite good) say 2.5" square, fold it enough times that when you lay it across the hole like an elephant trap it will overlap the rim, but not so much it prevents the drill from stuffing it right on in there.

Wet the rag (before folding) fairly liberally with top grade neat sulphurated cutting oil, and just plunge through it, using really heavy feed.

The rag compresses up and provides industrial strength vibration damping, plus the extra feed force preloads the bearings, quill feed etc, so the beneficial effect on chatter is quite surprising. The chips embed into the rag, if there's lots to come out you'll have to replace the rag a couple of times.
 
endmill

form grind an endmill (4 flute). Make a short section at the max diameter then back relieve it. Sounds like a lightening hole in a gear. What is the finish callout?
 
no specific finish call out. This is a gun part. If I had a compound slide I would attack it like that. I'll try packing the rest of the hole with rags, but keep in mind this is a through hole. I got to drive the chamfer about .231 deep. I've had very good luck with a countersinking tool, but they only come in 90 degrees.
 
Took a 35/64 drill and grinded the lips by hand on my belt disc grinder using the guide and it cuts without chatter or nothing and thats going dry. Thanks everyone.
 








 
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