98 Mauser barrel threads

[jmh54738]

To quote from "Gunsmithing" by Roy Dunlap, "The thread is approximately 12 per inch. The thread is not exactly 12 to the inch, but this is satisfactory for fitting. It is, of course, a metric pitch and does not convert perfectly to English measurement."
I have found the above statement to be false for those old actions that I have worked with. The TPI is EXACTLY 12, and of 55 degree, Whitworth form. With the lathe set up for threading 12 TPI, and with a dial indicator tip on the flank of the old barrel thread, the indicator dial stays steady as the barrel is turned. 12 TPI = .0833" pitch. If the barrel thread was 2mm pitch, (.07874"), then my dial indicator would gain .0046" per revolution. So my question is, Why do these German '98 Mausers have a 12 pitch Whitworth thread? Was the metric system not yet standardized? If I call this thread to be metric, then the pitch is 2.11658mm. Not exactly an even number. I love threads!!

[redneckdan]

At that time the metric system was not as widely used like it is now. Germany did not 'officially' change over to the metric system until around 1875. Even then some german regions held onto the old system. Paul Mauser was born in '38 and depending on where/how he was educated he might have picked up a preference for the whit worth style threads. I have no idea on the whys , but they definitely are a 12tpi whitworth thread.

[Linstrum]

Hi, jm54738, like you say, the threads are Whitworth and have its typical 55º profile and thread form including inch pitch. The Mosin-Nagants I have worked on also have Whitworth-type threads, as did the one m96 Swedish Mauser I did barrel work on. The reason why they all have Whitworth threads with inch pitch is because the best barrel making machinery at the time in the late 1800s was British and not set up to cut metric threads.

That faux pas by Roy Dunlap is quite unusual for him, he was darned good most of the time. I suppose he made the error because he assumed that because Mausers were made in Germany and Germany used the metric system for most of their threads that Mausers therefore had metric threads. Wrong!

Also, part of it was as rdneckdan said, Germany had not switched all the way over to metric yet like France had.

I do threading often enough so that I made a lathe threading tool sharpening jig for my bench grinder to sharpen both 60º and 55º profile angles. See:

http://castboolits.gunloads.com/showthread.php?t=67723&highlight=threading+tool



rl983

[jmh54738]

Very good information, Guys. I read all of the old posts. I made two jigs for grinding threading tools in my surface grinder, one 60 degrees, and the other acme. The 60 degree jig has the clearance built in, just flip it from side to side on the magnetic chuck and the job is done. The clearance on the acme jig is dialed on after trig-ing out the helix angle of the thread and then adding a few clearance degrees. The following side of the acme tool is a negative angle minus some clearance. The jig does the 29 degrees. Consideration must be given to the fact that the helix angle at the OD of a thread is not the same as the helix angle at the root. I have cut hundreds of multiple entry, left hand, internal, acme threads in aluminum bronze; being spindle nuts for industrial valves. Aluminum bronze is very tough, the tool just screeches through the metal. For some reason, manufacturers use stainless nuts on stainless spindles, and they gall up and destroy each other in spite of anti-seeze compound. I haven't bothered to learn pix posting on this site. If interested, you can PM me an email address and I will send pix. The coarsest thread on my big lathe is 1/4 thread per inch...think of that... 4 inches per turn. I love threads.

[akajun]

Dont know if its true, but I had always heard that the reason European Mausers were built with Witworth threads was theat they were built using English Machinery, because that was what Mauser had in his shop and did all his testing on.

[jmh54738]

Regarding threads in our U.S. civil war era weapons, I recently read that some of those were metric. Do you think that that was because of the French connection, with supplying either arms or tooling? I don't yet want to start taking guns apart to study the threads. I also understand that many manufacturers made totally bastard size threads so that they were the only supply source. For instance, the gears on my older LeBlonde lathe are an uncommon 9 diametrical pitch.

[Linstrum]

jmh54738, I like doing threading a lot, too, I have a Jet 13x60 lathe with all the different switch gears including the 120x127 metric conversion gearing besides the regular threading transmission gear box. I have yet to find a thread that I cannot match closely enough to work, including 55º 19 tpi British Taper Pipe and 17 tpi threads. That the pitch angle is slightly different at the root than at the crest is a fact that a lot of machinists don't get right off, it is steeper at the root and the difference in steepness depends of the thread depth. Believe it or not, I learned about pitch angle being different at the root as a young child by using the children's corkscrew slide at the park, where the slide ramp was too steep for me to climb back up at the inside of the turn while at the outside of the turn the angle was slight enough for me to climb back uphill!

The Civil War era guns that had metric threads probably had several origins, one being that the lathes and tooling were from Switzerland, Belgium, and/or France. Another was that the guns were made in those countries, notably France and Belgium. The Confederate States got guns any place they could, especially England since England had a vested interest in the South winning its secession.

You are quite right about each 19th Century manufacturer having its own thread systems, although I have run across US-made nuts and bolts from the 1860s that were the same as National Coarse except for the 1/2", which originally was 12 tpi instead of the 13 it is now. Despite the National Coarse pitches (same as British Whitworth pitch threads except for 1/2", plus having 60º profile angle) Thread profile angles were all over, too, 45º was common at one time and still is in England for miniature screws like are used for clocks. The Brits have their own bicycle thread screws, too. The camera tripod thread used on all US camera bases is alos a bastard size, I think it is a 1/4"-20x 45º profile, although I regular NC 1/4"-20 fits well enough and is okay in my experience.

By the way, I just hate that our National Thread System is going by the wayside, we have a perfectly good system of threads that won World War Two, built The A Bomb, and got us to the moon! I have a bunch of Butterfield, Cardinal, etc, taps and dies that can't be replaced with the crud and craption coming from China! I bought a bunch of taps and dies made in China that are a waste of steel, they won't even chase existing threads!

Besides Acme Threads, what other threads do you do? I am interested in what you have to say because I have looked at and duplicated by hand grinding the tool bit for the thread used on Garand barrels, which appears to be the 10º angle version of the "square" thread profile at ten tpi. I want to get the thread correct before I cut it on a new barrel for one of my Garands that I want to change over to .338-06).


rl985

[rtracy2001]

By the way, I just hate that our National Thread System is going by the wayside

I am not boke up about switching to SI threads and measurements as the SI system is much easier to work woth than US customary. I just wish we would pick a system and be done with it. Every time I try to work on something, I hate having to juggle two sets of tools.

The decline in quality you mention has nothing to do with the SI. It is more of an epidemic of the loss of craftsmen in favor of disposable goods and high volume production. Most everything today is meant to be used, then thrown away. (When is the last time you heard of someone going to a TV repairman?) IMHO, it wasn't the system that won WWII, or sent man to the moon, it was people who worked hard and truly believed that what they were doing was right and worthwhile. Something that it apears we have lost in recent years. (sad this is coming from a 34 year old, not an old timer)

[David2011]

I've personally seen plenty of Mauser actions rebarreled with barrels threaded with 60 degree 12 pitch threads. They will work at 60 degrees but if you have or can make a 55 degree gage it would be the way to go. The pitch is 12 per inch by my thread pitch gages. Good luck and have fun!

David

[jmh54738]

Linstrum, I put a Garand barrel on the optical comparator; it is hard to balance and keep steady. The thread form and depth look a lot like "Stub Acme". As to other threads that I have cut....plastic extruder dies with buttress threads, square threads as on Marlins and Springfields, Edison base (light bulb), the corrugated thread as on flexible waveguide, and those cut on a DP (diametral pitch) as for a gear hob. The really odd threads that I have cut have been with a form ground flycutter in a horiz milling machine, with the dividing head geared to the table to generate the pitch. I have done fittings for the fire department and various gas cylinder threads but I think that they were all 60 degrees. I did a 5 or 6 entry thread once. Just about any form is possible, whatever shape you grind the tool, so be the thread. I have always wanted to cut a level wind screw such as on an old bait casting reel.