Ancient Adjustable Twist Rifling Machine?

[Artificer]

Folks, I decided to split this into another thread so as not to take over the Original Hawken Rifle Twist thread.  This has to do with many 17th and 18th century rifle barrels being rifled one turn in the length of the barrel and whether or not they may have had an adjustable twist  rifling machine in the mid to late 17th century in Europe and especially in Germany and/or Switzerland, because that is where it seems to have been the most common in sporting rifles?

Back in that period, when Barrel Makers got large military contracts, they could have made a non adjustable rifling twist machine purely for those barrels in each contract.  If they made somewhat standard length barrels to sell for the hunting trade, they could also have made non adjustable rifling twist machines for each length of those barrels.  However, so many barrels were made in Europe that were one twist in the length of the barrel, it SEEMS to suggest that perhaps at least some barrel makers there had adjustable twist rifling machines? 

Dan (Dphariss) mentioned in the other thread where he wrote about the possibility of adjustable twist rifling machines, “Also its entirely possible they had more sophisticated rifling machines than were generally found in the colonies.”  Dan's quote intrigued me to do some research. 

OK, time for my disclaimer.  I am not a real machinist and those who are have my profound respect.  So if someone who has more machine knowledge than I and notices where I screwed up here, please correct me. 

I am under the working assumption that some kind of Sine Bar Lathe or Machine would be needed to make an adjustable twist rifling machine?   If that’s true, then three things would have been necessary, I.E. 1. At least somewhat precisely made gears, 2.  Some type of Sine Bar and 3. A lathe that could have cut at least a somewhat precise machine screw thread.   

Gears seem to be the least problematic as some fairly precise ones were made in Ancient Greece and Rome.  I ran across one account of an early 14th century clock that had been made with gears and NO screws, so I think we can discount gears?

As to some type of sine bar – this seems a lot easier than I first thought.  For those who don’t know what a Sine Bar is, here is a video of an early Mid 19th century Robbins and Lawrence Armory Sine Bar Rifling Machine.  http://bulletin.accurateshooter.com/2013/10/video-animation-shows-how-the-cut-rifling-process-works/

Unless I’m mistaken and I certainly could be, the hardest thing for a 17th century Barrel Maker to make an adjustable twist rifling machine would be whether they had an accurate way to cut a metal machine  screw thread on a lathe. 

I admit I was surprised when I found this “SCREW-THREAD CUTTING BY THE MASTER-SCREW METHOD SINCE 1480”  http://www.gutenberg.org/files/31756/31756-h/31756-h.htm

The next link gives a great overview of the advancements of screw cutting lathes and notes that many were highly guarded secrets earlier than we might imagine.
http://homepages.ihug.com.au/~dispater/turning.htm

Of course none of this information leads us directly to an adjustable twist rifling machine from the 17th century.  However, it seems to show there COULD have been one as the technology seems to have been available, if even as a most carefully guarded secret.  Perhaps why that is such a machine has not yet been found?  Or perhaps such a machine was discarded or “salvaged” to make other things in the late 19th or early 20th century wars? 

I hope some members find this interesting as I did.

Gus

[okieboy]

 Gears are not necesary for a sine bar machine, the sine movement can be transferred by a cord, such as wire rope, to a shive attached to  the rifling mandrel.
 Why would a sine bar machine require lathe cut screws?
 This is very interesting.

[Habu]

I really don't think an adjustable twist rifling machine was necessary to produce the range of observed rifling twists; several guides fitted to the same rifling machine would effectively accomplish the same task. 

Without pulling the breech plug, it can be hard to tell the exact twist of a barrel.  It is easy to be off a bit.  That gave the original maker a bit of a fudge factor.  A guide with a twist of 1:18" might be "just right" for a barrel 17.5"-18.5" or even 19."  Using the lower estimate of 1" range in barrel length, we are at needing 30 guides to cover the range from 18"-48". 

A maker could have a set of guides to match whatever barrel lengths/twists he commonly used, adding guides only when needed--and when building on spec, match barrel length to the guides on hand.  Depending on the type of rifling machine, a guide can be made with as little tooling as a couple of poppets, a plane, a saw, a chisel, a chalkline, and layout tools.  The poppets hold the blank while using the plane to "turn" the blank round.  Layout the twist with the chalkline and layout tools, saw the edges of the groove, and chisel them out. 

I'm not saying they couldn't have had some sort of sophisticated adjustable rifling machine, just that there are simpler explanations. 

[Artificer]

Gears are not necesary for a sine bar machine, the sine movement can be transferred by a cord, such as wire rope, to a shive attached to  the rifling mandrel.
 Why would a sine bar machine require lathe cut screws?
 This is very interesting.

If the rifling guide was adjustable for both rate of twist and length as well as adjustable for the number of grooves, would that not require gears and machined screws?   
Gus

[Artificer]

I really don't think an adjustable twist rifling machine was necessary to produce the range of observed rifling twists; several guides fitted to the same rifling machine would effectively accomplish the same task. 

Without pulling the breech plug, it can be hard to tell the exact twist of a barrel.  It is easy to be off a bit.  That gave the original maker a bit of a fudge factor.  A guide with a twist of 1:18" might be "just right" for a barrel 17.5"-18.5" or even 19."  Using the lower estimate of 1" range in barrel length, we are at needing 30 guides to cover the range from 18"-48". 

A maker could have a set of guides to match whatever barrel lengths/twists he commonly used, adding guides only when needed--and when building on spec, match barrel length to the guides on hand.  Depending on the type of rifling machine, a guide can be made with as little tooling as a couple of poppets, a plane, a saw, a chisel, a chalkline, and layout tools.  The poppets hold the blank while using the plane to "turn" the blank round.  Layout the twist with the chalkline and layout tools, saw the edges of the groove, and chisel them out. 

I'm not saying they couldn't have had some sort of sophisticated adjustable rifling machine, just that there are simpler explanations. 

Habu,

I agree it could have been done by making individual guides for each length of barrel, though a few more sizes would be necessary to make rifled pistol barrels in various lengths and I realize they were MUCH less common. 

Perhaps they made new guides as required when they got an order for a different length barrel than they usually made?  But, what I'm not sure of is would that have been cost effective for one or even a small number of barrels ordered?

Gus   

[okieboy]

 Rate of twist is adjusted by changing the angle of the sine bar. To do different lengths of barrels requires your guide to be as long (or slightly longer) as the longest barrel you cut, shorter barrels just don't hang off the back of the machine as far. The number of grooves is controlled by an "index" at the head of the machine that positions the mandrel to different rotational positions, in a 5 groove the positions are at 72 degrees each, in a 7 groove these would be at 51.4 degrees, though it is possible to divide an index using dividers without any reference to degrees. An index with 12 notches could do 2,3,4,6 or 12 grooves on a single index plate and it is not unusual for an index to have changeable plates or to have 2 or 3 plates attached in a stack   
 Also there is no need for the bump system to raise the cutter by rotating a screw, the cutter could be adjusted by the shim addition method. 
 There are some photos available on the internet of sine bar machines at Friendship. There is a photo of Noman Brockways sine bar machine in i believe Dillon's book, it is extremely simple and does use the rack and pinion system.
 This all makes me wish that we could get together and build machine to try everything out, want to come visit Minnesota?

[Habu]

Perhaps they made new guides as required when they got an order for a different length barrel than they usually made?  But, what I'm not sure of is would that have been cost effective for one or even a small number of barrels ordered?   

Figure a half-day's labor (6 hours) to make a single-groove rifling guide using the tools as I described; less if the maker knows what he is doing.  (I know it can be done that way, and how much time it took, because I made one that way before I was old enough to be allowed to use the lathe in the school shop--and I was figuring it out as I went.) 

I think it was Flintriflesmith who said to figure 100 man-hours of labor to make a hand-forged rifle barrel start-to-finish.  Making a new guide as described wouldn't add much to the total time involved.  It would obviously be a greater percentage of time if rifling a purchased bored-and-ground blank, but still not so much as to not be cost-effective. 

[Artificer]

Rate of twist is adjusted by changing the angle of the sine bar. To do different lengths of barrels requires your guide to be as long (or slightly longer) as the longest barrel you cut, shorter barrels just don't hang off the back of the machine as far. The number of grooves is controlled by an "index" at the head of the machine that positions the mandrel to different rotational positions, in a 5 groove the positions are at 72 degrees each, in a 7 groove these would be at 51.4 degrees, though it is possible to divide an index using dividers without any reference to degrees. An index with 12 notches could do 2,3,4,6 or 12 grooves on a single index plate and it is not unusual for an index to have changeable plates or to have 2 or 3 plates attached in a stack   
 Also there is no need for the bump system to raise the cutter by rotating a screw, the cutter could be adjusted by the shim addition method. 
 There are some photos available on the internet of sine bar machines at Friendship. There is a photo of Noman Brockways sine bar machine in i believe Dillon's book, it is extremely simple and does use the rack and pinion system.
 This all makes me wish that we could get together and build machine to try everything out, want to come visit Minnesota?

I must be having a senior moment as I can't figure out the use of the wheel and cable and pulleys to get different rates of twist.  Looked for the photos of the rifling machines at Friendship and that didn't work.  However, I did find this thread talking about the wheels and pulleys, but I'm afraid it still didn't sink in.  It is reply number 9 by John Taylor:  http://castboolits.gunloads.com/showthread.php?147639-Building-a-Barrel-Rifling-Machine

Thanks for the offer to visit in Minnesota.  Been a LOT of years since I've been that far North.  Not sure if I could stand the temperature anymore as when I returned from Somalia in the early 90's, I froze all the time even in the middle of a California Summer.

GUs

[Artificer]

Perhaps they made new guides as required when they got an order for a different length barrel than they usually made?  But, what I'm not sure of is would that have been cost effective for one or even a small number of barrels ordered?   

Figure a half-day's labor (6 hours) to make a single-groove rifling guide using the tools as I described; less if the maker knows what he is doing.  (I know it can be done that way, and how much time it took, because I made one that way before I was old enough to be allowed to use the lathe in the school shop--and I was figuring it out as I went.) 

I think it was Flintriflesmith who said to figure 100 man-hours of labor to make a hand-forged rifle barrel start-to-finish.  Making a new guide as described wouldn't add much to the total time involved.  It would obviously be a greater percentage of time if rifling a purchased bored-and-ground blank, but still not so much as to not be cost-effective. 

VERY interesting.  Thanks for the further info.
GUs

[okieboy]

 The cable and pulley or the rack and pinion do not themselves determine rate of twist. The angle of the sine bar alone determines rate of twist. When the rifling mandrel moves forward, it moves the rack and pinion forward, but because the sine bar is at an angle, the slider on the bar which is attached to the end of the rack not only moves forward, but moves laterally towards the mandrel and causes the pinion to rotate.
 If the sine bar was adjusted exactly parallel to the mandrel you would cut straight rifles because the rack would not move.
 Suppose that your mandrel was 48" long, and that the pinion (or shiv) had a pitch diameter of 4" (approx. 12" circumference), then to get a 1 in 48" twist you would have to adjust the back of the sine bar 12" out of parallel. The slider would move 12" as the mandrel moves 48" and the pinion would rotate one full turn.
 Does that make more sense of it?
 Glad that you returned from Somalia.

[James Wilson Everett]

Guys,

A patent was granted to the sine-bar rifling machine, US patent number 7,178, March 12, 1850.  In the patent description the proir art is stated to be the fixed twist cylindrical cam style rifling guide.  The patent claims to be able to produce any twist - straight, any rate of twist, and gain twist.  I suspect that this was not the first time such a machine was used, but it appears to be the earliest patent granted.

Jim

[Artificer]

The cable and pulley or the rack and pinion do not themselves determine rate of twist. The angle of the sine bar alone determines rate of twist. When the rifling mandrel moves forward, it moves the rack and pinion forward, but because the sine bar is at an angle, the slider on the bar which is attached to the end of the rack not only moves forward, but moves laterally towards the mandrel and causes the pinion to rotate.
 If the sine bar was adjusted exactly parallel to the mandrel you would cut straight rifles because the rack would not move.
 Suppose that your mandrel was 48" long, and that the pinion (or shiv) had a pitch diameter of 4" (approx. 12" circumference), then to get a 1 in 48" twist you would have to adjust the back of the sine bar 12" out of parallel. The slider would move 12" as the mandrel moves 48" and the pinion would rotate one full turn.
 Does that make more sense of it?
 Glad that you returned from Somalia.

Thank you for the additional information.  I got confused when you mentioned a sine bar machine would not need gears and I thought that meant it would not have a rack and pinion - since the pinion is a gear and the rack is in effect a flat gear?
Gus

[Artificer]

Guys,

A patent was granted to the sine-bar rifling machine, US patent number 7,178, March 12, 1850.  In the patent description the proir art is stated to be the fixed twist cylindrical cam style rifling guide.  The patent claims to be able to produce any twist - straight, any rate of twist, and gain twist.  I suspect that this was not the first time such a machine was used, but it appears to be the earliest patent granted.

Jim

Thanks James,

I was hoping you might chime in, since you have extensive knowledge and personal experience of early screw making and gunmaking technology.

Might I ask if you think the 17th and 18th century barrel makers used different guides for different length barrels as Habu made such a good case for, or do you think they may have had some sort of adjustable twist rifling machine that they most likely kept secret in an age before patents really protected them?

Gus

[Swampwalker]

I thought the 'sine bar' was used for gain twist, while a straight bar offset at various degrees was used for conventional rifling. 

[James Wilson Everett]

Guys,

The only firm evidence that I know of where a gunsmith used different cams for the same rifling machine comes from the Fry brothers gunshop, Ligonier PA, late 19th c.  Here is a photo of the second cam or guide.  It is an rough rifled barrel that would be mounted in bearings on the rifling machine.



And, here is the complete machine with a different cam or guide in place.  I assume that the two have different twist pitches, but I have not measured them.  I can think of no other reason for the two cams, except to change the twist pitch.



If anyone out there knows of another rifling machine of the period with more than one cam, let us know.

Jim

[Centrefire]

It is difficult to see how a sine bar could be used for gain twist rifling.   A method used by early European riflers  was to use a cord and pulley.  The set up is similar to a guide rod bench, except a wooden pulley was fitted over the barrel holding mandrel at the far end.   The diameter of the pulley was  "maximum rate of twist x  22/7."  (pie) About 85% of one full twist being the limit.   The cord went round the pulley and up to an overhead jockey pulley and down to a second pulley at the front end of the barrel.  The pull bar was either operated by hand or a crank, but there was a hook at the handles. The cord ran from the hook of the pull rod to the second pulley, then up to the first pulley and down to the big pulley on the mandrel.    A second cord was wound round a second groove in the big pulley in the opposite direction with a counter weight to return the barrel to starting position after each pass.  For standard twist, the cord ran perfectly parallel from the hook to the second jockey pulley.    For gain twist, the second pulley was adjusted up away from the pull rod parallel.  That is - if the hook was one inch up, the second pulley was more.   -    When the handles were in forward position, the angle of the cord in relation to the rod was greater than when the handles was pulled back producing gain twist.

[davec2]

If you twist up a flat or square bar, like the one shown on this Pakistani rifling machine, with a gain twist, it would be no problem to cut a gain twist in a barrel using original methods.