Subject: Radiator stop-cock thread

From: [email-masked] (Bill Webster)
Date: Wed, 01 May 1996 08:55:17 -0400

We've been talking about all sorts of weird thread pitches, metric, unc,
unf, coke bottles, etc.

So here's a new one.

Why is the thread on a radiator stop-cock left handed?
Is it a standard thread pitch?

Anybody know the history on this one?

regards.

-- 
Bill Webster   [email-masked]

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From: [email-masked] (W. Kaiser)
Date: 2 May 1996 17:40:23 GMT

> Anybody know the history on this one?

My guess about left handed is that we're used to tightening things by 
turning them clockwise, and counterclockwise to loosen them.  The 
stop-cock has a hollow stem that the water drains through, so it is 
tightened by being screwed outward, rather than inward.  A left handed 
thread screws out-clockwise and tightens the valve to shut off.

I had one of these from my furnace apart the other day to free it up.  It 
looked like about 1/4"- something, maybe 28 or 32.  Since my furnace is 
working again, I'm not going to take it off to see what the thread is.

--
Bill Kaiser
[email-masked]

There are three ways to do a job: good, cheap, and quick.
You can have any two.
A good, cheap job won't be quick.
A good, quick job won't be cheap.
A cheap, quick job won't be good.

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From: [email-masked] (Richard C Lucas)
Date: Thu, 2 May 1996 18:13:38 GMT

Here's my guess....

The ones I'm familiar with are a hollow screw with a closed flange on the
inside end which seal by tightening this flange against a seat.  The hollow
screw has some holes in it near the flange which allow the coolant to come out.
The left hand thread allows you to open the stopcock by "unscrewing it."  
If you used a r.h. thread, it would open up as you tightened it.

Someone once described left-hand threads as "the more you tighten it, the
looser it gets."

By the way, my air compressor tank has this kind of drain on it.

Dick Lucas
[email-masked]