Whitworth Threads?

scatgo

I lost that part of a bleeder valve on a 100-year-old cast iron radiator. I was going to buy a screw at the hardware store and turn it down in my lathe but its not metric or SAE. I don't have a clue if any of the bleeder valves i see for sale with 1/8 or 1/4 NPT will fit and I am scared witless at the ide even trying to remove the old bleed valve because i don't want break anything and make my situation worse. Any body have a clue as to where I can get that part?

mattmia2

probably proprietary to whoever made that valve.

EBEBRATT-Ed

Just take the old bleeder out and replace the whole thing. They seldom break. If they do which is unlikely you just drill and tap it going a size larger if you have to. Most are 1/8" so drill and tap it for 1/4" Ips. But it is not likely to break.

109A_5

You have a lathe. A properly outfitted Lathe can cut threads. Measure and match. Maybe dabble in the Machinist's Handbook a bit.

" not metric or SAE " maybe the old USS (United States Standard) or UNC (Unified National Coarse).

Intplm.

Many times you do not need a drill if the bleeder threads break off inside. Often, you can set the tap inward and turn it with the broken piece still in the hole.

RascalOrnery

Bspt and bspp fittings are still used I the industry. You could probably find something nominal of mcmaster Carr or something and modify it.

AlaskaDick

It looks a lot like an acme thread and valve stems are an application where acme threads are used.

Grallert

With a snuggly fitting wrench the bleeder body should come right out. You could use a torch to heat it up first. If it breaks a reverse twist drill of the correct size will likely remove what's left behind.

Pumpguy

Imperial threads ( Whitworth, and USA threads like SAE, NC, NF, USS, are determined by the number of threads per inch. On the other hand, Metric threads are determined by the number of threads per millimeter.

Whitworth threads have a 55 degree angle and rounded crests and roots. Metric and our USA threads are of 60 degree angle.

The best way to determine the pitch of a thread is to use a set of machinist's thread pitch gauges. I frequently use a tap with a known thread pitch as a gauge to determine the pitch of a thread I need to measure.

Knowing the pitch and the OD of the thread is what's usually needed to determine the actual thread size.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1904092#Comment_1904092

you can also measure a couple with a micrometer or caliper and divide by the number you measured, then invert if you are using tpi instead of the actual pitch to measure the thread.