Zerk grease fitting in steering box?

I found a old post about how to do this and did not save it and can not find now. I know that they used a 1/8 zerk fitting, I need to know what size drill bit i need to use and then tap it. Thanks Robert

 

Need Help- Steering Gear Box 90W oil leak

...:Handshake...

 

That was fast, and makes sense, your the one that wrote it. Thanks this will be a big help.

 

Hello, in the post it said to get a 21/64 drill bit to drill the hole but, thats much bigger than 1/8? did you mean 7/64? Thanks robert

 

......maybe...
it was a copy and paste of a post Earl made...

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I suspect you used an 1/8" pipe thread tap, which would require a hole larger than 1/8".

 

It would have to be smaller, because if the hole is bigger than 1/8 then the 1/8 zerk would fall in the hole and not grab to the threads. 21/64 is a little bigger than 5/16 which is bigger than a 1/4 which is two times bigger than an 1/8.

 

Steering gear mod...

 

Zerk fittings use tapered (NPT) pipe threads. I think the 1/8" Zerk refers to the thread size. Could be wrong. But, if that's right, 1/8" NPT tap needs an R (.339) drill. See the table below. Notice all the drill sizes are much bigger than the NPT size. That's because the NPT threads go on the outside of the pipe and the pipe size is the inside diameter of the pipe.

TAPER PIPE SIZES - NPT

TAP DRILLSIZE
1/8-27 R
1/4-18 7/16
3/8-18 37/64
1/2-14 23/32
3/4-14 59/64

21/64 drill is .328, maybe close enough. :Handshake

 

Hey, I did not realize the pipe threads are bigger and you are right, it takes a Taper size of 1/8-27 and I found out the drill bit size needs to be 5/16. Thanks for all your help.

 

Got er' done

Here's a pic of the finished fitting!! Thanks for all the great infor!!