-3 Brake Master

SoCalPlaneDoc

SoCalPlaneDoc

New member
I have a -3 Cruisemaster whith what appears to be the Paramount brake master cylinders. They look like this one:
V1-2-15-625-S_887.JPG

One of the reservoir plugs on mine are missing, the plug that is on the other one looks like someone installed a tapered pipe plug with a drilled hole for a vent. That works but I've been unable to identify the thread. anyone know what it is?
It didnt match anything in my local well-stocked hardware store. Looks like the thread is 28tpi but the diameter is slightly larger than 1/8 and much smaller than 1/4.
 
I would remove the other plug and then use a pitch gage and caliper to find out what is used. I also would take that plug to the local A&P and ask him if he has one of these in his stash. If no luck the power of the INTERNET will find you a plug. If you find out the dia. length and pitch let us know and maybe we can help with our stash. Lynn the crate :)
 
All good suggestions
I'm an A&P/IA, M/S in Mechanical Engineering, and design surgical robotics for a living.
I displayed the existing plug to the team of machinists who work in my lab, among them a Brit, another German trained.
I measured it, consulted two editions of the Machinery's Handbook, and a fastener standards reference (the name escapes me at the moment). It's 28TPI but the diameter doesnt match up with anything. The taper appears to be the same a NPT.
It's really not that big of a deal, I have a number of alternatives for the application but now, it's personal :) Actually we're all curious about it now. I thought I'd ask the braintrust here. The guys in the shop voluteered to make a pair with a knurled head, I'm going to take them up on it.
Photos I've seen of other masters show a plug with a hex head - mine has a hex socket for an allen key. I 'spose it's possible the taper isnt necessary and the originals had a straight thread... I dont want to take the masters out bad enough to see.
 
Earlier I said it was larger than 1/8NPT.. it's actually smaller, enough that wear isnt the reason...
Sorry about that.
 
It's obviously British Standard.......
If this is a top fill reservoir and the plug is in the fill port, The fit is not important. I have several in use that are plastic, vented by a 1/16 hole. Get 'er done.
Dan
 
ya no, it's not metric, or whitworth, or BPPT (that's why I had the euro-mechs in the lab chime in).

I'm thinking it's not the right plug for the hole anyway.. it was a fun mystery.

New plugs are done, brakes go back on today.
 
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