Step drills and mechanical fasteners

H

Hesparus

Joined
Oct 31, 2004
Messages
1,442
Hi Everyone,

I have been wanting to try some mechanical fasteners on my knives, so I bought a step drill bit from harbor freight and some aluminum corby bolts (1/4") from texasknife to try it out. I drilled a hole with my new drill bit in a piece of scrap material, but the corby bolt doesn't fit (the hole is just a tiny bit too small). The bit I used claims to be the same size as my corby bolts (or at least the size texasknife claims they are). Texasknife sells a step drill bit that they claim works with the bolts I bought, but I want some assurance that it will work before I go buying more tools.
My questions:
1) How much variation is there in the size of step drill bits (that claim to be of one particular size), and how much variation is there in the size of corby bolts and other types of mechanical fasteners? (I know that harbor freight probably isn't the best place to buy high quality drill bits, so I'm prepared for this to be the source of my problem.)
2) How common is this problem in other people's experience?
3) What do you recommend I do in this particular case?
Thanks,
Chris
 
Same size hole won't fit same size object!

Your bit needs to be a .001-.003 larger (depends on the run-out on your drill) than the fastener.
 
Never used any from TKS, however, I have used many, many handle bolts and the step drills from Pop's Knife Supplies. They fit right the first time, every time. There is a small learning curve as to how deep to counter-bore, but after a couple of practice holes on some scrap, you will get it right every time.

Robert
 
I just had a post about the same question and the overwhelming response was for Pop's and my searches affirmed the same. The advice I received was 1) use Pop's 2) whoever you use, get the bolts and the drill from the same place.
 
I don't know exactly what your parts look like, but you can sometimes reduce the diameter of a screw head by spin grinding it. Chuck up the shank of the screw in a portable drill and spin the head against a belt traveling over a rubber contact wheel. Using fine belts can produce a highly polished surface.
 
You should buy the step drill from the same source as the Corby bolts.

I didn't know HF sold step drills ( You learn something new every day). I find HF tools useful, but their exact tolerances are often a bit off. Corby bolts need the right size holes....or they won't fit.
 
+1 on Pop's. I just ordered some Corby's and a counterbore from Pop's yesterday. He told me he makes his Corby's himself and has had nothing but good feedback using the counterbores with his Corby's. Give him a call and talk with him.
 
Thanks for the advice, everyone. I guess I'll have to buy another drill bit or two. As for grinding down the ones that I already have, how do I chuck them in a drill without damaging the threads?

Chris
 
Use a threaded rod or cut off bolt for the female, and a piece of threaded tubing or standoff for the male.
 
you could rap a few turns of masking tape over the threads then put it in a drill doing it up very lightly then spin the head agants a flat block with some 600 wet and dry till you have the right size
 
Got my Pop's corby's and step drill today. Exactly what I wanted and they look great. I've held and used bolts from 2 other suppliers. What I didn't expect was for Pop to email me and find a way to save me money on my shipping. Now, the original shipping was high, but I expected to pay it and I signed the dotted line. Nice surprise.
 
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