Bolt Holes

[EricH]

Originally Posted by Ninja_Bait

Ah, I understand the ire now. I knew it wasn't a GOOD method, but I was suggesting it as a LAZY method. I'm sorry I have encouraged laziness in the FIRST community, and will recant my previous two posts on this thread.

(Though if I'm tired and frustrated around week four of build season, I may choose to use a drill gauge on a bolt. I'm sorry, I just can't stop myself. )

There is a "better" lazy method. Compare the screw to the drill bit shank, right next to each other. If the shank matches the screw size, then you should be all set. If the hole is too small, find the next drill size larger (or a non-working student or mentor with a rat-tail file or similar device) and make the hole large enough for the bolt.

Can't tell how many times I've used that to find the drill bit that best fits small screws used to attach servo stuff to R/C airplanes...

[PAR_WIG1350]

Calipers work too, just use the flat parts, not the tapered portion which could slip in between threads and give an inaccurate measurement.

[Retired Starman]

There are other reasons to drill holes larger than necessary for the bolt in question. A 14-20 bolt will easily fit in a 1/4 in. hole, but if the hole is in aluminum, once you have tightened the bolt, you have deformed the hole so that the bolt will be difficult to remove and reinsert the next time.

In different applications, hole clearance varies. For precision machines, specified clearance is less than for architectural use, for instance.

Use of a good, appropriate chart is suggested.

Dr. Bob