I am doing a little fab work and I need to get my hands on some metric drill bits. I haven’t found anywhere local yet that carries them. I need bigger ones, specifically 12 and 14mm. I found a few cheaper sets that carry 8-10 but they didn’t have anything larger. Since I only need 12 and 14 I would rather buy the bits singularly. And they need to be good bits that can handle steel and cast iron. Any ideas where I can poick some up locally?
May i ask what you’re doing that is so precise?
12mm = .472 but 15/32 = .469 which is -.003
14mm = .551 but but 35/64 = .546 which is -.005
Chances are the drills will drill slightly oversize anyway, so you would probably be REALLY close with SAE bits…
Unless you’re doing ultra precise clearancing, I can’t see why +/- .005 would hurt you. Also, If you’re doing work that requires you to be more accurate than that, you wouldn’t be buying basic store drills.
Its for a custom brake set-up using metric bolts. I would like to have it as close to the proper size as possible. Rather not take chances with the brakes. I’d actually rather have the hole a bit small so its too snug rather than too large and have a bolt back out.
Tolerance for 12 mm -0/+0.07 FYI
So I take it standard would work fine?
I’d also ask are you going to be using a mill or good drill press on these? If you’re planning on doing it with a hand drill you’ll have some “wobble” and your tolerance will go right out the window anyhow.
How are you locating these holes, and what are you using to drill them?
I’ll be using a press.
I’ve done that a lot for metric thru-holes and it always works out good…Who doesn’t like things to be nice and tight 
My tolerance was for a drill bit not a mill.
A mill is the only way to get anything closer, but your not using a drill bit there either.
You will be fine especially with a drill press.
std clearance holes will be fine. The hole is just a size, and dosn’t care if a metric drill bit drilled it out now, same for the bolt. For the hole placements try to use you caliper, and bracket, anything that has the bolt pattern getting used. Transverse punch that pattern, and step drill to the final size on the drill press.
Lol.
Anything that you’re going to pass a bolt through does not need to be metric.
Thanks guys. :tup:
FASTENAL.com if you are looking for metric drill bits locally