Thread size for forge blower oil fitting

[RAT]

I'm just now getting around to cleaning up a Royal Western Chief forge blower and need to make a plug for the oil fill hole. I poured a lead slug and turned it into the hole to get an impression of the threads. The best I could figure out is that they are 7/16-28. I wanted to check with some more experienced members to verify this before I order a special size tap for the extra fine thread.

[Smoketown]

Check with a Harley Davidson Motorcycle shop.

The old pans and knuckleheads used a lot of 7/16 fine thread hardware.

Wheel hub to drum brake bolts comes to mind. Head bolts too.

Most old bike mechanics are intrigued with 'old iron' of all kinds and would probably chase the threads for free.
(Although 6 packs were ALWAYS welcome.)   

Cheers,
Smoketown

[tiswell]

RAT,
    Check the lead slug for taper. If the thread is tapered it could be a pipe thread.  An 1/8-27 tap measures 7/16 at the shank.

                                                                          Blessings, Bill

[Ben Quearry]

My old Western Chief has the original brass stop cock, instead of a plug, that you open to verify that it has oil in it. I think it's a pipe thread, looks like a tiny steam fitting.

Ben

[RAT]

Thanks... by the way I meant die... not tap. Slip of the keyboard. That's what I get for posting after my bedtime.

I was wondering if it was a tapered 1/8-27. I have a die for that. I bought a grease fitting with that thread to try it, but it was too small.

By the way... the petcock is there... it's the bolt-like plug where you fill the oil that's missing.

[RAT]

Just to end this topic... and for future reference if anyone in similar need searches in the future... I found a brass plug in the plumbing section at ACE hardware. It's a 1/8-27 pipe thread. It fit perfectly.