Tapping dom

I need to tap a hole in dom tubing for a 5/8-18 rod end.
The drill for this size is 37/64.
I have a 9/16 drill,that is a 1/16 smaller then the 37/64.
Will the 9/16 drill work?

 

Not a chance , with fine threads , it going to be tight !

 

use the correct size drill

 

There are two diameters involved in a thread, the minor and major. The drill size specified for a particular thread diameter and pitch is the smaller of the two. The tap then cuts threads to the larger of the two. The tap has no ability to INCREASE the size of the bore.....only to cut threads in the CORRECT size bore.

Buy the correct tap and save yourself time and GRIEF!

 

Most tap specs are for 75% threads and as such they really need to be drilled to the spec'd size. I think you'd have a hard time getting that thread cut correctly without the right size drill.

 

Try it on a piece of scrap just to see.

 

I tried it and the tap broke in half

 

No !!!

 

It's actually only 1/64" smaller but, you should still get the correct size drill bit.

 

Get the right bit.

A good hardware store or even HF will have it in a set.

 

u will break the tap

 

Good luck finding a 37/64" drill bit at HF. Its not really a standard size found everywhere.

 

Thread taps are not designed to cut on the minor diameter so if you were able to start the tap then is would eventually become a press fit in the under size pilot hole and the tap would seize.

 

Buy, borrow, or steal the correct bit!

 

go to a machine shop that has the ability to put 2.5" of thread depth in that tube. you ain't going to have much luck by hand. they will have a quality tap that won't break off too.

 

^^ oh damn just noticed it was over 1/2" diameter. My bad.

OP, Maybe try a hardware store that sells the tap & tap drill as a set, or McMaster-Carr?

 

Why not? Ive been doing it for years, well over 1000 holes, never broke a tap. Most guys that make their own RR and steering drags have as well.

 

Always use tap fluid (oil).....and no tranny fluid is not tap fluid, neither is motor oil, hydraulic fluid, rhinocheros sperm ,or anything except tap fluid!......are you hand taping? Or lathe? Critical to be absolutely straight!.....drill cant be all that expensive.....ya beg borrow or steal, oh and get the tap fluid too.

 

I did this 12 years ago on another project and have the right hand and left hand taps.
I just couldn't find the 37/64 drill that is the reason for my question about a 9/16 drill.
After looking where I never would have put it ,it has been found.
I will drill with my H F 16 speed drill press and hand tap it.
When I did this 12 years ago a machinist made a tool it start the tap straight and I still have that.
Thanks for all the replays.