Drill bit sizes

[Silent Assasin]

Ok, so in the process of my new case build, I bought one of those tap screws that thread nearly any metal with a drill bit. They had several that came packaged with a drill bit to drill the hole first and then drill the threading. But for more then half the price I could be just the threaded drill bit, so I bought it at around 2.50. My reasoning is that I've got a garage full of litterally hundreds of drill bits and several friends and family members with the same situation as me, I was sure that I could find the correct size drill bit. So anyway, I got home opened it up and it says to use with a #29 drill bit... Then I thought, wtf, I've never even heard of people refering to drill bits as #'s. So anyway the thread drill bit I bought is for #8/32 sized screws, anyone happen to know exactly would diamter drill bit to used? After comparing a couple of bits, it seemed like 9/32" drill bit fits the best but it didn't fit exactly right, the first hole I drilled with it, the start of the thread was wierd. The other sizes I tried just didn't work. 1/4(Next size down) it made the threaded bit grind and I was a fraid of stripping. The next size up didn't give enough threading for the screw to catch. Is there some bit size in between that refers exactly to #29 drill bit? I even went back to the hardware store and looked, and they didn't sell any idividual drill bits by the # nor did they have a chart or anyone that could tell me what size that actually is.

 

[Nivram]

Okay, 30 seconds on Google found me this page , which shows that a #29 drill bit falls between a 9/64" and a 1/8" drill bit in size.

If you don't have the correct size, it's always better to go a little larger in size, so use a 1/8" drill bit. Why? Because, as you said, if the hole is too small, the beginning threads can be a bit weird (because the tap can't get down in the hole far enough). You actually went well over 1/4" with a 9/32" drill bit, but I'm figuring you meant 9/64", right? Cuz a 9/32" hole would give you a lot of "wiggle room" all around the tap, and make it impossible to thread the hole, since the tap cutting threads wouldn't even touch the sides of the hole.

Remember, in the future, Google is your friend.

 

[Lt. Dan]

Dood, wait till they spec a "letter drill bit" that's gonna fry your noodle. There are fractional drill bits 1/4 3/8 1/2, there are letter drill bits that follow wire sizes 1-80, and there are letter drill bits A-Z and then there are Metric drill bits. Gottem all

 

[TechLarry]

No kidding...

I bought this massive Titanium Drill Bit set from Cosco that has ALL sizing versions of bits. Lettered, Metric, US Fractional, a bit for every size and type.

I stare at it trying to figure it out, but haven't got there yet.

At least it has the good old US fractional section

-Larry

Dood, wait till they spec a "letter drill bit" that's gonna fry your noodle. There are fractional drill bits 1/4 3/8 1/2, there are letter drill bits that follow wire sizes 1-80, and there are letter drill bits A-Z and then there are Metric drill bits. Gottem all