Clearance Drill For 10-32

randyc said:
I think there is a typo, shouldn't ".13" actually be ".013" ? Pretty cool expression, I've never heard of it before :)
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Indeed, one decimal point off makes for some excellent crashes (-:
I have no idea why I remember that to this day, aside from probably having an odd curiosity about old standards and measuring systems. Go figure
 
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rwm said:
I use a lot of 10-32 screws. The diameter of this size screw is published as 0.190 nominally, Although some seem smaller. Based on this nominal diameter they will not fit through a 3/16 (0.188) hole. What diameter do you use to drill clearance holes for these? Is there a metric size that works well? Any other ideas?
R
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You need to determine what you need from the clearance hole. Do you need the holes tight for lets say close but not perfect location? or does it really mater that much? Lets say you have 4 holes that need to secure a block. If you have no clearance on the holes then your block with the holes as well as the part with the tapped holes must be in perfect location or your screws will not line up and bind. Screw holes are not usually for alignment, only to secure the part, if you need to be able to remove your part and put it back on exact location you need to either dowel it in location or have some way to locate it prior to bolting in down. In most day to day jobs we do the hole locations are within + or - .005. If a hole pattern is off to the extreme then we would need .010 clearance to line holes up. For this reason we usually make drilled holes for screws .015 larger than the screw we are using.
I hope this helps.

Brojt
 
Good thoughts. Clearly depends on the job at hand. The issue I had was 3/16 doesn't clear and 13/64 (.203) was too sloppy for my liking. It was for a bolt handle on an AR. I will be using a #9 (or maybe #11) drill when I need a nice tight fit.
R
 
In my days at Lockheed we used number 10 Number drill .1960. For 8-32 I think it was number 21.

Look up number drills. While you are at it look up letter drills as well for full understanding of USA drill sizes.
 
Just some follow up. I bought a couple of #9 drills and they fit a #10 screw very nicely. If you are not doing this I recommend it. No more imprecise 3/16 drills for me.
R
 
Thanks for the link. That chart is a lot easier on my eyes than the small one I have.
 
Use 7/32" same as .224 in decimal fraction.This one fractional size larger than a tapped hole.Your tapped hole should be
.190 for 75% thread.This is slightly more than 3/16" or .187.
mike
 
Since I have a bad habit of losing charts, and I can't be bothered with looking something up on the net, I do it the simple way.
I just keep trying the screw in different holes in my drill index until I find a hole that fits about right. If I am aiming for a tight fit, I drill a piece of scrap and test fit.
 
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