Steering box casting. radiator drain p-lug

[countershaft]

Gotta a bad drain plug , been working with a stub of a plug and lock pliers, no good. It just won't move, nothing left to do but drill 'er out and tap. Any body know the drill and tap size ? Is it standard pipe thread?

[John *.?-!.* cub owner]

3/8 pipe thread. Try welding a nut to it and see if you can trun it out that way.

[countershaft]

Good idea John, but I can't weld.

[Donny M]

3/8-18 NPT (National Pipe Thread) Use a 37/64 drill bit. Work with a small drill bit first and incrementally increase the size to 37/64.

[countershaft]

Dommy m , a 37/64 would be over a 1/2 " Is that right ?

[Donny M]

Yes .578125" to be exact. The diameter of 3/8 pipe is .675" Sounds strange, but true

[beaconlight]

Not strange when you consider pipe is measured inside dimension (ID)

Bill

[brichter]

measured inside until up to 4 inches then it goes outside (i think i am remembering that right. my memory is getting older than I am.)

[Phillip W. Lenke]

I agree with cubguy 47 Heat may be the answer. Will break up the rust
If you have a small propane torch use mapp gas a hotter flame.
Good luck!
PWL

[Rudi]

Don't forget to use the Loctite Never-Freeze goop. The proper name escapes me , but when it does pop into my brain , it will edit and insert. As far as the Iron style plug - Brian has a point, but if you use the Never-Freeze or what ever it is, and the plug has been painted - there should not be a problem.

I welded a nut - took about 10 tries to get it on right - but the combination of the heat, and the added area of the nut helped get the plug loose - with the help of 2 feet of sked 40 pipe on my wrench - popped out real easy like.

[John *.?-!.* cub owner]

When you install the new ones you can get brass plugs from many autoparts stores. Correct Police may not approve, but once it's painted it's hard to tell.