My curiosity- has anyone used double-start threads, perhaps for a take-down application?
For instance, a double start 6 TPI would have a pitch of 1/12" (0.0833) while having a lead of 1/6" (0.1677)


The idea would be to have rapid assembly engagement of the 6 TPI thread with the relative strength of 12 TPI.

I was tinkering with the idea on my lathe and wondered if any maker had used such threads...

Thompson Center uses a triple start thread on their muzzle loader breech plugs. basically you can remove a one inch screw, in a couple of turns.
I have thought about it for a take down bolt action as well. Problem is, they are not easy to cut male and female threads. And it would have no real advantage that I can see. Takedown in three seconds instead of 8 for a full threaded shank or one second, for a half interrupted one.
I like the idea though.

In a breech plug scenario on black powder break action rifles a triple leade screw thread could allow quick breech loading of break action rifles with paper cartridges. Much like a Sharps. No need to muzzle load.

quote:

Originally posted by dpcd:
Thompson Center uses a triple start thread on their muzzle loader breech plugs. basically you can remove a one inch screw, in a couple of turns.
I have thought about it for a take down bolt action as well. Problem is, they are not easy to cut male and female threads. And it would have no real advantage that I can see. Takedown in three seconds instead of 8 for a full threaded shank or one second, for a half interrupted one.
I like the idea though.

I think you'd basically use the cross-feed only, with the compound parallel to the center-line of the barrel (or receiver)
You'd have to leave the half-nut engaged the whole time.
After cutting the first thread, you'd advance the compound 1/2 of the lead and cut the second thread.
Pretty involved, but the same process applies to female threads as well as male.
Like I said- just a curiosity I had while tinkering..

Right,, Bob; the Ferguson breech loading flint lock had that. Vertical screw breech, but with only 1.5 turns to open.
I was going to convert my TC to use brass cartridges but haven't yet, but it would be easy.
Chamber for 50-110. Leave the primer out. I was going to solder the brass to the breech plug, for extraction, and have two of them for quick loading.
And I think CNC mill would the the easiest thing to use....

quote:

Originally posted by Dulltool17:
My curiosity- has anyone used double-start threads...

No, but that sounds like the perfect thing to do on a gun. I always said that if I get a CNC I'm going to build my gun stuff completely non-standard, because it's a gun. I'm talking 3-start, left hand, 18.7TPI by 28.4mm, interrupted modified edison thread form, etc. Try and find that at the hardware store.

Really though, with a 2 start thread you could flip the barrel over and shoot upside down and the sights should still work. If you want quick engagement some sort of tapered thread would be better, like a pipe thread or the breech plugs on some of the big artillery pieces. One turn and you get 6 turns of full thread engagement.

155 Howitzer breeches are just interrupted threads, and the 120mm M256 Tank Cannon is a falling block like a Sharps. So, nothing new there.