Caplock Drum Thread Size

[Mule Brain]

I am looking to replace this drum, it is still working but......

What is the thread size on this? It isn't modern thread, and tracks drums don't look close enough.

 

[LilysDad]

Can you measure the length of that thread and calculate how many threads per inch that would be?

[Scota4570]

You need a thread pitch gauge and a caliper to play with old guns.  Measure the major diameter.   Measure the threads per inch.  Look it up on the old interweb. 

I'm not trying to be difficult.  Nobody can tell you by looking at a picture.  The threads could be anything, UNF, UNC, Metric, or some odd bastard size.  IF you can't do this, any competent machinist can measure it and tell you. 

You can also try nuts on it.  Take it to a well stocked hardware store and see what fits. 

 

[Daryl]

It looks like 1/4 x 20 or so, but it is hard to about impossible to tell from a picture. Might even be smaller than that. Looks quite small.

[Mule Brain]

You need a thread pitch gauge and a caliper to play with old guns.  Measure the major diameter.   Measure the threads per inch.  Look it up on the old interweb. 

I'm not trying to be difficult.  Nobody can tell you by looking at a picture.  The threads could be anything, UNF, UNC, Metric, or some odd bastard size.  IF you can't do this, any competent machinist can measure it and tell you. 

You can also try nuts on it.  Take it to a well stocked hardware store and see what fits. 

 

Dang, forgot about the thread pitch gauge. I have one somewhere, and will try and find it.  Tried the thread tests metric and english, and no go on both.

Couldn't find the gauge, but found three drums, and one is real close but the thread spacing isn't the same

 


caring smileys

[Daryl]

You may have to go larger and re-tap the hole, is all. I've be considering a much larger drum diameter.

[Mule Brain]

You may have to go larger and re-tap the hole, is all. I've be considering a much larger drum diameter.

If I can't find one, i will have one made that will fit it.

[Gaeckle]

Is that off an antique barrel? That thread size looks coarse.

[Dphariss]

Get a thread pitch gauge. A good hardware store should have one. And remember that MODERN drums MUST be supported by the lockplate since they are invariably made of cold rolled and are shock sensitive.

Dan

[Dphariss]

You may have to go larger and re-tap the hole, is all. I've be considering a much larger drum diameter.

If I can't find one, i will have one made that will fit it.

If you have it made then have them use hot rolled low carbon steel.

Dan

[kudu]

cant tell by sight , Whats it off-gun wise?

my machinist eyes say 5/16-18

[Scota4570]

https://www.custompartnet.com/tap-size-chart

Years ago,  I printed out a chart from here that has both English and metric.  I stapled it to the wall. 

An experienced lathe operator can make a new drum of any size or thread pitch.

[Mule Brain]

cant tell by sight , Whats it off-gun wise?

my machinist eyes say 5/16-18

Here it is

https://americanlongrifles.org/forum/index.php?topic=65176.0

[Clark Badgett]

A lot of the older guns used threads that are long out of use now. I forget what it's called, but a 55* thread with rounded threads was common, I think it was an English style thread.  Modern SAE and Metric threads are 60*, not counting Acme styles.

[Tim Ault]

A lot of the older guns used threads that are long out of use now. I forget what it's called, but a 55* thread with rounded threads was common, I think it was an English style thread.  Modern SAE and Metric threads are 60*, not counting Acme styles.

   I believe that's the British witworth type thread it was 55 degree rounded top and bottom of the thread

[jerrywh]

It is near impossible to tell from a photo. Still no answer for what kind of gun??

[Mule Brain]

It is near impossible to tell from a photo. Still no answer for what kind of gun??

Heavy barrel match rifle