[How do I?] Grind A Drill To Drill Smaller..?

EmilioG

EmilioG

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I need to drill a 17/32" (.5313") through in 1/4" aluminum. The hole needs to be a few thou under 17/32".
Closer to .5300 or .5210"?
Is there a way to touch up the drill on a belt sander so it will drill a smaller hole?
I don't have time to bore the hole and there are no under size 17/32" reamers.
Can this be done? I was thinking that maybe the flutes on the sides of the drills cutting edges can be touched on the belt sander? I know most drills cut over size, so..?
Thanks
 
You can put the drill in your mill chuck and spin it backwards and stone it down a bit. Be careful and warned however, that you lose all clearance on the lands and this makes it easy to seize the drill up in the hole.

Put an oily rag under the drill to catch the abrasive, it will shed some.
 
I'd suggest a 13.5mm drill, but I don's suppose they are that common, it would be over-sized by .000149
 
T Bredehoft said:
I'd suggest a 13.5mm drill, but I don's suppose they are that common, it would be over-sized by .000149
Click to expand...

I need the hole to be under size by several thou. a 17/32" drill is 13.49, a 13.5mm drill is going the other way, larger.
But thanks.
 
Tony Wells said:
You can put the drill in your mill chuck and spin it backwards and stone it down a bit. Be careful and warned however, that you lose all clearance on the lands and this makes it easy to seize the drill up in the hole.

Put an oily rag under the drill to catch the abrasive, it will shed some.
Click to expand...

We have an old drill bit grinder at work, if I can find the 17/32" collet for it, maybe I can use that.
But maybe chucking it in the BP then touching an india stone or arkansas stone to the sides? Taper?
It only needs a slight touch or maybe I can find a cheap 17/32" that is under?
 
Sure, there could be taper. But if it is back taper, it will benefit you. I doubt you will find even a cheap drill that actually measures much under. If you stone a drill down with back taper, predrill with a smaller drill so the point won't factor in and induce wobble (oversize), you will have a cheap sub for a reamer. You won't get the finish that a reamer leaves, but you didn't mention finish requirements.
 
You should be able to get a reamer in an undersized standard size, you would need to drill it first so would add an extra operation and tool.

Stuart
 
pre drill with smaller drill
take a drill one size under 17/32 and grind one of the cutting edges larger than the other one
 
EmilioG said:
I need to drill a 17/32" (.5313") through in 1/4" aluminum. The hole needs to be a few thou under 17/32".
Closer to .5300 or .5210"?
Is there a way to touch up the drill on a belt sander so it will drill a smaller hole?
I don't have time to bore the hole and there are no under size 17/32" reamers.
Can this be done? I was thinking that maybe the flutes on the sides of the drills cutting edges can be touched on the belt sander? I know most drills cut over size, so..?
Thanks
Click to expand...

You can lay it on a piece of crocus cloth and sand the OD with a forward and turn stroke to tale a bit off the OD. with a per drill hole it will cut close to the micrometer check size... but with just drill in from scratch will cut larger. A drill cut off and inch and sharpened will cut often .001 smaller , you can check it down length to find size.
 
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