Diff cover plug size?

[FLUndertaker]

Motobilt replacement diff covers. The hole measures 58/64”. The plug that screws into it measures 1.04”. The back of the bung is marked as pictured, 3/4. What size tap do I need to run thru it to clean the powder coating out of the threads? Pipe threading measurements is Chinese arithmetic to me. A 1” tap is way to big.

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[kevman65]

3/4" NPT tap.

That is a pipe tap and may not be available at a hardware store.

If you have a plumbing supply house nearby, that would be best bet. Be ready, they're usually not cheap.

 

[kevman65]

Now, if you can get a hold of a solid, 3/4" steel pipe plug, you can run that in and out to clean the threads. Go slow, use some oil.
Do NOT get a cast iron or malleable iron plug. They can and will bind and break.

 

[FLUndertaker]

Now, if you can get a hold of a solid, 3/4" steel pipe plug, you can run that in and out to clean the threads. Go slow, use some oil.
Do NOT get a cast iron or malleable iron plug. They can and will bind and break.

I have a plug thAt requires a 9/16 Allen wrench to tighten. Problem is that when I had the covers powder coated they didn’t do a great job protecting the threads in the cover so I now can’t get the plug started into the bung

 

[kevman65]

I wouldn't use the plug for the diff cover.

Like I said, a solid STEEL pipe plug, it has a raised square to tighten it. Do not use any form of iron plug.

The pipe tap is going to be in the $30 range, the steel plug in the $1 range.

I can't tell by the picture if you can do it, but you might try going from the backside. If it's a solid shoulder on the back side of the bung you won't be able to do it.

 

[whiteglad]

Harbor Freight has sets of pipe taps priced reasonably.

 

[Renegade]

I wouldn't use the plug for the diff cover.

Like I said, a solid STEEL pipe plug, it has a raised square to tighten it. Do not use any form of iron plug.

The pipe tap is going to be in the $30 range, the steel plug in the $1 range.

I can't tell by the picture if you can do it, but you might try going from the backside. If it's a solid shoulder on the back side of the bung you won't be able to do it.

If it’s NPT, it will be tapered, so you shouldn’t be able to thread an NPT plug in from the back.

 

[kevman65]

If it’s NPT, it will be tapered, so you shouldn’t be able to thread an NPT plug in from the back.

Bungs are generally too short to be tapered. They engage on the last few threads of what you're threading in.

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