Testing Single Point Thread Fitment

[alecsParticipant @alecs]

<p style=”text-align: left;”>30 TPI in all sorts of diameters was used by old time gun manufacturers, often with Whitworth thread form for some reason.  Ive no idea why.</p>

[DiogenesParticipant @diogenes]

Aha – ‘ Traditional crafts’ – I should have expected as much..

[Diogenes]

On Diogenes Said:

Aha – ‘ Traditional crafts’ – I should have expected as much..

Guns, and everything else, were manufactured along non-standardised traditional craft lines until lateish 1800s. It was the Springfield Armory during the US Civil War 1860-65 who pioneered standardised mass production, so gun parts were interchangeable in the field. The practice rapidly spread to other industries and jumped the Atlantic to the heart of the Industrial Revolution in the UK.

Despite good old Joe Whitworth inventing the first national thread standard 20 years earlier, it hadn’t yet caught on to a widespread degree. The US civil war also brought the w idespread introduction of breech loading repeating rifles, so many old percussion cap muzzle loaders are quite likely to have been made in the “traditional craft” era with who-knows-what threads used at the whim of the maker.

Then there were manufacturers who deliberately used non-standard threads so as to monopolise spare parts supply.

 

[berwickParticipant @berwick]

Thank you ALL, for taking the time to offer your thoughts and for sharing your experiences and knowledge. I do appreciate it.

Steve101,

Yes, Peter Dyson and son. I learned about them (and their 30 tpi nipples ) when researching any info on a 30 tpi thread form. The nipples for Trantor revolvers are 30 tpi, but too small major / minor to fit my gun. I contacted them three times asking to purchase custom-made nipples, but have not received a reply from them, to date.

Anyway……

Onward with my project.
I have made three taps / thread chasers now. The first two screwed right in, but both were still a loose fit. The third, worked. It did not actually cut metal, but re-formed or cleaned up, the existing percussion cup threads to a known pitch, thread depth, major and minor. And, the hole is now round and true, unlike before. I’m calling the percussion cup clean-up “done”.

Next task, is to modify the threads on an over sized nipple that was purchased, to match the percussion cup. Me thinks that this is the easiest path forward, vs  turning a nipple from W-1, from scratch. But, the challenge that must be met is how to hold the tiny nipple in the ml7, so the threads can be re-cut and so that the nipple ( and holding tool ) can be removed from the lathe spindle and periodically checked for “ fitment” in the percussion cup.

No, i do not trust my skills, my measuring abilities, nor my best guess at turning these tiny threads correctly for good fitment, in one go.  So being able to remove the nipple for fitment checks and to return it onto the spindle for further cutting, is a must.

How would you go about devising a “holder” for this process, on a ml7? Please keep in mind that I am a beginner and whatever tool, collet, jig or holder will be a new, first time adventure in machining for me.

 

As per the pic, please note the size of this nipple and its unique form where it must be securely held.

I have ER 32 Collets in standard, but none of the collets have the hole sized to .308”, the nipple collar dia.
Nope, got no broaching tool, and i have no idea how to make a square hole ( to match the nipple shoulder ) anyway.  Hand filed?? Maybe….. but it is tiny and my attempt at hand filing such a tiny square hole would likely be laughable.

Drill chuck on MT 2, inserted into lathe spindle? Three jaw drill chuck on a 4 sided square nipple, probably not.

 

Some sort of brass nipple holder, with epoxy or soft solder, or? to fill in gaps and offer enough support  and rigidity to permit cutting these threads, while withstanding corresponding single point tool friction?

A spindle hand-crank will be used for turning.

 

Thank you for your advice! 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[berwick]

On berwick Said:

[…]  As per the pic, please note the size of this nipple and its unique form where it must be securely held.

[…]

 

Some sort of brass nipple holder, with epoxy or soft solder, or? […]

 

 

Forgive me for leaping into the discussion

Shellac should do the job nicely

MichaelG.

[Author]

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