Interupted screw breach

[Thorn]

Ok guys i need some help. I would like to see more interupted screw breach loading guns.

so far the only info ive been able to find on the net is:
That the first interupted breach was made by the Italians in 1845. The first were considered four motion, where all the threads were the same length, with equal width non-hreaded sections. These breach blocks were comparitativly long as half of the thread was cut away to alow withdrawal, thus reducing their capacity to withstand firing stresses. The four motion seem to have been removed completly between firings.

The next development seems to have been the three motion breach plug which while still long, it used a hinged carrier ring. Here is an example of this.
http://1919a4.com/forums/showthread.php?t=1158&page=2

The Welin breach block was invented some time in the 1890's, it is the modern breach block seen today, a short easy opening breach with interupted threads of varius lengths.

While it will be a while before i can build anything, i would apreciate any imput and/or corrections.

[moose53]

Most people don`t have the equipment to make a Welin breech block.And removing threads in the breech receiver with out making a mess would be a lot of fun! I have found that the Whitworth system to be the easyist and most practical for sport cannon shooting.

[Double D]

You might touch base with our British Bros. in arms at Muzzle Loaders Association of Great Britain-Cannon Board[/color] Bill curtis seels plans for Brtish  Guns and may include breech loaders.

[moose53]

Now you have my curiosity up.Just how did you plan to remove the internal sections of threads from the breech receiver?I have only seen one cannon made with a interupted screw breech.It was a 40mm out of California and he milled through the bottom of the receiver into the top to make a two section breech

[Thorn]

thats just it,......I would like to see if anyone has made any. Im assuming it could be done with a milling machine and a rotary table, but im not a machinist.

[Double D]

Seems to me some i have seen had a breech ring that the barrel screws into.  The breech rign is just broached to remove the threads. 

That's my guess.

[moose53]

DD, do you remember at all who had the cannon?I would very much like to see it and find out how much trouble it was to make.

[Double D]

Yeah it  was the Usa Family that had a bunch of them.  As In US Army, US Navy and US Marines.

http://www.nps.navy.mil/se/harney/cbt3ch12.pdf
 
http://fas.org/man/dod-101/sys/land/docs/GDO2FA/sld038.htm

http://fas.org/man/dod-101/sys/land/docs/GDO2FA/sld039.htm

[Michael Az]

I would imagine a ring would be broached like Double D mentions. It would have to be for production because having the broach made would cost thousands but uncle sam could afford it. If a fellow wanted to make just one in his shop, I don't see any reason a shaper couldn't do the job with an indexer. There are even shaper attachments for Bridgeports.
Michael

[moose53]

I know the Army has interuped screw breeches but have you seen anyone make one for a black powder cannon?

[GGaskill]

Having never seen one of these mechanisms in person, are they really threads (meaning, do they advance with rotation) or just a series of parallel grooves (which would be adequate to lock a breech.)

[moose53]

It never occurred to me that they might not be threads.It would sure make it simpler to make the complex curve of the ogival cone breech.

[Double D]

Yes indeed they are threads, a tapered thread.  You need lead to cam the block clased and the taper

  From: http://www.nps.navy.mil/se/harney/cbt3ch12.pdf

In an interrupted screw breech block, the breech block is threaded as a male piece with
threads on the outer diameter, while the breech is threaded as a female piece with threads on the
inner diameter.[2] The breech block is screwed out of the breech for loading and screwed into the
breech for firing. However, to prevent the necessity for rotating the breech block through many
complete revolutions to attain a seal, part of the threads on both pieces are machined away. Rather
than having a continuous helical groove, each turn is broken up into three or four short arcs of thread
followed by equal arcs where the threads have been machined away. See Figure 12-3. When the
threads on the male piece are aligned with the threadless portions of the female piece, the male piece
may be fully inserted into the female piece without turning. At this point, rotating the threads by
a small fraction of a single turn will cause all of the male threads to engage all of the female threads
and form a closure with the ability to resist strong axial forces. Turning the male piece a fraction
of a turn in the opposite direction disengages the threads and allows the male piece to be withdrawn
for loading. Rather than axially sliding the male piece axially into and out of position, it is common
to place the male piece on a hinge while retaining its ability to rotate about the axis. The male piece
is swung into and out of position, and then rotated to engage or disengage the threads. To facilitate
the rotary motion, both male and female pieces are slightly tapered. A cylinder can not be rotated
into a second hollow, tight-fitting cylinder. However, a truncated cone can be rotated into a second
hollow, tight-fitting truncated cone.

THe next paragraph is on obturation and show basic design.

I am trying remember back 20 years and recall who had the intetrupted thread breech cannon.  Doug Titus of Redding CA comes to mid, but I know he had a Whitworth. 

I also recall a small breech loading cannon made from the receiver ring of a 98 Mauser.  There is a very basic interrupted thread screw breech...the Mauser action.

[moose53]

The only interupted screw breech that I know of was made by Jim Dilling out of Eureka Cal. I think that information is right.It was a 40mm mountain rifle and photo was taken in 1981.                                                                                                                                                                                                

[GGaskill]

I was specifically thinking about the Welin design.  The plain interrupted thread design is a true thread.

The Mauser really is not a thread design as the lugs only advance/retract for a fraction of the bolt rotation, not continuously like a screw thread.  The only action I know of that used a true interrupted screw thread was the old Newton action of the 1910's.

[Michael Az]

How about a Remington 788?
Michael

[GGaskill]

In my opinion, the same; just more locking lugs.  They still go to perpendicular (to the bore axis) motion after leaving the cam section.

[Double D]

I was specifically thinking about the Welin design.  The plain interrupted thread design is a true thread.

The Mauser really is not a thread design as the lugs only advance/retract for a fraction of the bolt rotation, not continuously like a screw thread.

Wrong, George, the Mauser locking lugs are a screw thread.  You can even feel them cam in when you close the bolt. The when you open the bolt you can feel them go go loose before the root of the bolt hit the primary extraction cam.  The Mauser bolt action has all kind of little neat things about it like that.  Didn't they teach you that in College, they did in mine!

[GGaskill]

Re. the Mauser, I respectfully disagree.  I have one (a M98) in front of me and the locking lug arrangement in no way resembles a screw thread.  It has two surfaces, the closing cam and the locking face.  A true thread would have a continuous helical surface.

[The Shootist]

DD The cam action you refer to may be the feel of the "Cock-on-Close" mechanism of the Mauser.

[jeeper1]

Pre 98 mausers were cock on closing. The 98 mausers are cock on opening.

[Cat Whisperer]

Semantics.

The inclined lead-in of bolt lugs are just very stout, short areas of 'thread'

[Double D]

Gentlemen this is no pet theory of mine. It is fact. The bearing surface of the 98 Mauser locking lugs are an interupted screw thread. It has lead. I didn't know it until I studied firearms design in college.  They even presented the pitch. Don't recall what is.  The purpose was to apply additional force to seat a cartridge in dirty chamber and give extra strength in chamber lock up. 

Everything about the Mauser is brilliant and has a purpose, even the sloppy open bolt, so it won't bind in the dirty field of combat.

The 98 Mauser is your priemer Modern Assualt rifle!

Interrupted screw thread breech cannons use the same principal to seat and seal.  I noticed inthe PDF from the Navy that an extra element is added the thread is tapered to facilitate closing.

(Edited to avoid confusion-Edit in italics)

[Thorn]

Well after reading this discussion: http://yarchive.net/metal/artillery_thread.html 
Im starting to think that the Welin breech block may be a little too complicated. 

Which leads me to think that the next best thing would be a three motion breech like the ones shown in my link at the start of this thread.I dont suppose any of you know who made those guns?

[Michael Az]

Thorn, after reading that summary, it does appear it takes a special machiene to do the job. I did a search looking for that photo but couldn't find it. It also appears they used a Higby cut at the end and start of the threads from the description. {To aid in engagement} I also wonder if the thread is a multi start to aid in fast engagement. Sounds like a nightmare with conventional machinery.
Michael

[Double D]

Let me clarify something here about the Mauser.  The whole locking lug is not a thread, it is the locking lug bearing area that is part of a thread.

I am going to edit my post above to make that clear.

[GGaskill]

I think you could make a small one on a conventional lathe in a home shop scenario, although the procedure would be absurd for full size production.  There I would expect a machine somewhat like a shaper, although the work would be moved instead of the cutter.

In a home shop, I would first turn and thread the maximum diameter, then mill out the smaller ones (no threads yet.)  Then chuck the block in a 4 jaw.  Disengage the motor (put it in "neutral") and set up a stop that aligns with the ends of the steps in the threads.  Then hand turn the chuck with the half nuts engaged at the thread pitch you want.  Work the chuck back and forth advancing the cutter to cut the thread to full depth (you might have to back out the cutter if there is a lot of play in your lead screw.)  Then back out the cutter, disengage the stop and advance the chuck a full turn to work on the next thread.

Hard, boring, manual work in the extreme but possible using existing equipment.  Probably not as bad as it sounds for a small breech block.  The breech ring would be done basically the same way with exceptions for internal threading.  The barrel would screw into the breech ring.

[Cat Whisperer]

Let me clarify something here about the Mauser.  The whole locking lug is not a thread, it is the locking lug bearing area that is part of a thread.

I am going to edit my post above to make that clear.

There are many flavors of threads that only bear against it's mating surface in one direction.  The 'back side' is often of a less functional angle. 

It's a thread.  It has a 'camming action'.

[Victor3]

If I'm not mistaken, all one would gain by using this design would be a bit of speed in reloading. What's the hurry  ?

 Strength of the breech is decreased by removing a large portion of the thread, so a beefier design is required to make up for that. It would be cool to be able to take the back end off of a cannon with just a 1/4 turn, but is it really neat enough to justify building it? Maybe, but I'd think if I were to make a breech-loader, it would use a full diameter thread. Maybe a double or tripple start if I wanted to spin it off faster....

[Double D]

I can think of two reasons to do it...one you wanna see if you can do it and see if you can make it work and because you just want to.