how much bigger does a drill bit drill?

[Rcdizy]

If I want to drill a hole in stainless, and press fit a 3/16, O1 drill rod (.1875) into it....

What drill size? numbered, lettered, decimal?

 

[Ed ke6bnl]

my guess is a number 13 drill .1850 lot of times drill will drill oversize holes that may work for you. but lets hear from some real pros.

 

[Ulma Doctor]

+1 on the #13 bit

 

[Bob Korves]

Drills do not make holes to an accurate size. Drills do not make round holes. Drills do not make straight holes. All that said, the #13 might do it for you, depending. It also might end up too tight, or might possibly end up loose, depending... A drill one size smaller, #14, followed by an appropriate reamer for the desired press fit, would make for a lot less guesswork and a lot more confidence in a good outcome. You should also carefully measure the O-1 rod diameter with a trusted micrometer or compare it with a 3/16" dowel pin. O1 is usually within .001" of nominal size, but is definitely worth checking, especially at the end of the rod. Check it at several clock positions, too. In a hole of that small size, there is less room for tolerance stack up if you want a specific fit.

 

[chips&more]

Using a drill bit for holding correct hole position and or for making a specific hole size and or making a round hole is a crap shoot.

 

[Rcdizy]

The #13 was too loose still, Size smaller too tight.

The rod is excactly .1875

So in a perfect world, what reamer?

Would locktight work in this type of application?

 

[Wreck™Wreck]

Excellent question Dr. Suess, .1865

 

[mikey]

I would bore it. Right size, straight walls and you can decide the tolerances for the press fit.

 

[RJSakowski]

In my experience, drill rod is often slightly smaller than nominal size. How much oversize a drilled hole is depends a lot on the condition of the drill. +1 on the undersized hole followed with a reamer. The size depends on the class of fit you require. Are you going for a tight slip fit, light press fit, or heavy press fit?

 

[Bob Korves]

Using a drill bit for holding correct hole position and or for making a specific hole size and or making a round hole is a crap shoot.

Chips, you said the same thing as me with a lot fewer words...

So in a perfect world, what reamer?

Totally depends on the actual rod size and the desired fit.