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

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...
A lot depends on how many holes you have to drill? A few , a lot or something in between, and to some degree how accurate they have to be. For just a few holes I would be inclined to drill the closest undersize you have and then file to size it is only aluminium. Try using a 3 corner or triangular file that is just a bit too big and turning it slowly in the hole will give quite a good finish as it slowly increase the size, measure the hole frequently as you go. If it's a lot then you have some choices, invest in an adjustable reamer, or make an undersize drill Using an old 17/32 bit set up in lathe and a tool post grinder to grind it accurately to size then relieve it behind the lands by hand or even set up a guide to turn the drill to get it more accurate. you only need to resize the drill a little over a 1/4 inch in length to do the job then you can always resharpen the drill back to its proper size.
 
I think I solved it. I bought a Criterion DBL202b and few Borite cobalt boring bars.
The smallest Borite bar bores a minimum of .2500
Thank you
 
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...
Reamers are purchased in decimal sizes in .001 increments as seen here https://www.mscdirect.com/product/details/02035301

Also between .530 and .521 is a considerable difference, do yourself and everyone else a favor and leave out the 4th decimal place, you are likely not playing that game.
 
Well, that 4th place is there ad infinitum...we just don't know if we can get the target we would like.
Doesn't hurt to aim high. I own a few reamers from Yankee and Alvord-Polk but the boring head
is something I will be using more often. I did make my holes for the clamps and they work perfectly.
The Criterion boring head is amazing. And, yes, Msc is a good vendor. I always wait for "up to" %30 off
sales. Funny thing is, it's usually %x off LIST price. Not always a great bargain.
 
Very cool. That cutter is prefect for making V slotted vise jaws cuts. And yes, you can bore a hole but look how much fun making a tool can be. I wonder if lathe bits can be made in a similar way? Nice video, Thanks for sharing that.
 
EmilioG said:
Well, that 4th place is there ad infinitum...we just don't know if we can get the target we would like.
Doesn't hurt to aim high. I own a few reamers from Yankee and Alvord-Polk but the boring head
is something I will be using more often. I did make my holes for the clamps and they work perfectly.
The Criterion boring head is amazing. And, yes, Msc is a good vendor. I always wait for "up to" %30 off
sales. Funny thing is, it's usually %x off LIST price. Not always a great bargain.
Click to expand...
I do not buy tooling from MSC unless they have it and other suppliers do not.
 
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