Gunmaker/Gunsmith's Tools

Out of interest as well as collecting shotgun cartridges I also collect the machines/equipment for reloading them. As many of them are well old very often the ones you manage to come across are broken, missing parts, missing screws, etc. So I am always making these missing parts which is a real challenge as the thread sizes are completely non-standard.
I have just been given a lot of old fashioned taps and dies, sadly a lot are broken but still very useful.

My question is does anybody have any old charts of thread sizes for gunsmiths/gunmakers screws etc.? or any information on threading or tapping sizes for them?


You will find that smiths made their own and “invented” as they went along.

For instance some smiths in Norway went decimal inches in the late 1820’s.
So instead of 12 scrupels and 12 lines for a total of 144 to the inch they went 10 and 10 for a total of 100. Mind you they kept the inch so they simply went bigger.

Here are more than you want to know and some charts of standard threads:

Here an original drawing of the Norwegian 12,7x44R cartridge but in decimal inches:

Chickenthief, thanks for that, I am ok with standard threads and stuff. What I find more intriguing is that for example they would use a (and I will use imperial sizes) mismatch of sizes. The pitch from a 5/16" (0.3125") BSW thread but on a 17/64" (0.2656") diameter screw, how crazy is that. Also if you look at their tools, they didn’t actually “cut” a thread is was more like cold formed onto the screw or into the hole. Looking at some of these tools I have just picked up many of the dies have burst on the back or actually split where too much metal has been forced into them to try and form the thread, the same problems you get with modern day thread rolling.
As most of the work was out sourced they must have had some tables (standards) to work to. I do have one but that does not fit with any that I am finding.

Chickenthief, please note that what you show here is not the Norwegian 12x44R rimfire. It is the 12x42R rimfire. Also, there is no such thing as the 12.7mm rimfire.It was originally known as the 4 line copper case cartridge.In 1879 our army adopted the metric system and then the cartridge became the 12mm copper case cartridge.

I seem to recall that the big Brownells Encyclopedia of Firearms (or some similar title- a massive book with dark green binding) has a listing of thread sizes for firearms. Mostly 20th century, but maybe others.


Two things :

  1. the standard threads are what I call “commercial” threads, meaning the ones which are the most common on manufactured items you find on the market.

But as soon as you deal with industrial companies you can have whatever the customer wants. He doesn’t care if it is standard or not.

To give you an non metric example (easier to understand for US people) I used to commonly make silencer threads of 1/2 inch not only in 28TPI but also in 20 TPI, 24 TPI, 30 TPI.

Aside from the 28 TPI (used for AR 15 for example) and 20 TPI (used for the 22 LR carbines) which are standards for silencers, some gun manufacturers want to control the market of the silencers to put on their weapon.
Some others use a left thread (Glock for example).

To keep a captive market I used to thread silencers with an 1/2 inch 28TPI but left thread.
Despite the advantage of avoiding the silencer to unscrew, it was nearly impossible to find in France 20 years ago (and still now) a mechanical shop which was able to make a 28 tpi thread (and left) if they had a conventionnal lathe.

Just to complicate a little more I have made for other applications, threads which have not a tringular profile but a square, trapezoidal, rounded or semi-trapezoidal profile.

in conclusion all depends of the customer.
If he is smart enough he has his own standard.
And it must be true also for your british reloading tools manufacturers.

  1. In France many people talk about “gunsmith thread” because they cannot find the equivalence in the nowadays standards.
    In fact it is false. The gunsmiths never used a special standard.
    The people simply don’t know the french standard changed when the ISO one was adopted after WWII.
    Or for example they don’t know a German mauser rifle has a british Witworth thread.


Attempts at standardization started early in the 19th century and there are many obscure standards. Some manufacturers used their own proprietary threads and still do, further muddying the waters. Many of the old tools swaged the threads other cut. I do antique clock restoration on the side and buy up old screwplates, taps, and dies when can do so reasonably.
Here I make screw making seem much more complicated than it really is:
Screw For Mainspring Winder


Nice one JP,

Totally agree with the use of the term “commercial” threads, these being British threads as BSW & BSF (both threads based on the Whitworth form of thread), American being UNF & UNC and Europe being Metric Fine & Metric Course, these being the most common found in their respective countries, yes there are many other BSB (British Standard Brass), ANF/ANC (American National Fine & Course), B.A. (British Association) there are plenty more that is just a sample of other used “commercial” thread standards.

Left hand threads are very simple, You simply turn the tool upside down and run the lathe spindle in reverse and then basically run the tool towards the head and up to a shoulder just as you would a standard right hand thread. Just be aware of screw on chucks with the lathe running in reverse as it will unscrew the chuck if you are not careful. Therefor quick release chuck systems are preferred.

As to your comment that “gunsmiths never used a special standard” I have to disagree with you on that one. However I believe it to be more than one standard. Below is an article on gunmakers threads gives an oversight into the type of tools used but is missing some information and I personally do not believe the dates to be correct as these tools were still being made and used at least up to the middle of the 20th century, in fact some of us still use this method now except that we screw cut the tap first and harden and temper it, then use this to cut the die.
I have a large selection of name branded taps and dies made that follow no “commercial” standard but are numbered (I have at least numbers 1 to 6 inclusive and no they are not B.A. sizes) makers are such as G Walker. and others and the style is standard as are the thread sizes.
Sorry the full size picture is slightly out of focus,

Typical tap,

Makers Name

If you look at the top picture you can make out the thread on the right hand end, this has four flats and is really a former rather than a cutting tap.


Very interesting, I have a few questions for you please as you seem to have the same tools as I do;
1). Do you have any formulae for working out the size of the blank portion prior to threading (forming).
2). Have you tried making the blank portion fit into the hole diameter of the size above?
3). What material was the screw made from?


hello Eightbore,

  1. I never said left hand threads were difficult.
    Just needing a little bite more of skill .

The biggest problem, as I pointed out, was (and still is !) to find in France (i am talking about gunshop or small mechanics shop) a conventional lathe which has the good gear wheel.

  1. From what I have seen, all the threads people were complaining about on a french guns (for screws and so on), were in fact used at the same period of time by the industry (either french or british).
    But I have not seen all the guns…


As far as I know there are existing 125 different types of threads (basic forms) not talking about the different sizes.
Many of the threads are related to specific industries i.e. gas cylinders, oil industry…
As a standard reference tool for threads i would recommend the machinery handbook. Older versions are also ok because there were just minor changes in the national and international standards.
I especially like the tables in there because they give you the possibility to identify threads.



Hi JP,

Yeah we are the same here, to do metric you have to change the gears, you need to add a 127 tooth gear or a combination to get it, 127 being the lowest full number of teeth to give 25.4 (mm to inch) 5 times 25.4 = 127.simplest way to explain it I can think of. There are of course other ways to achieve the change of pitch. My lathe is different but cannot remember with out going out to the “man cave” what they are!!



I have issue 10, 16 and 21 of the Machinery Handbook and no mention of Gunmakers threads in any of those! The only list I have (or rather had, can’t find it at the moment) is by B.S.A, I did see a small list of sizes in another book but cannot remember what book it was. They are based on the Whitworth form but non-standard pitch to diameter relationships.



What’s needed is ‘translation gears’ a 127T and a 50T inserted into the gear train. 127 is a prime number.

I find this thread (no pun intended) fascinating as I’ve had an interest in taps and dies for many years. Having worked for many years in manufacturing clothing, we came across many taps specific to an industrial sewing machine manufacturer, such Union Special of the US. They were also fond of using UNEF threads (UN Extra Fine).
All the brass threads I came across were 28 tpi regardless of diameter. I like oddities (must be the collector instinct) so was even happy to find left hand twist high speed steel drills for which I had no use.
I did have a 30" half tolerance lathe, but unfortunately didn’t learn how to cut threads with it.


I am running of memory here but I have it in my mind it is a 127 & 100 tooth that is needed? I would need to dig the book out to be 100% sure, I have not done it by change gears for years, I just used to get on a metric lathe. I know you can use other combinations that will get you very close, so close that to all intent and purpose it is correct. It is all proportional to the TPI of the leadscrew as to what gears are used to get there.


I seem to recall Jim B having photos of screw samples on plates,
I’d dig the out but as some stuff he sends can’t be published, & I never bothered to put those in a separate file, I can’t send along. Ask him.

British gunmakers for the most part in the early days before standards made their own screws, for their own guns.

I know he sent me one on nipples which was very interesting but can’t recall any on screw samples. I will ask Jim, thanks.

Yes, early doors they did make their own screws, I apricate that but as you say that was before standards. As the Birmingham gun quarter expanded during the mid 1800’s as you know it became a workhouse of hundreds of small businesses for the out source of parts, Action filers, Stockers, Barrel filers, Lock makers, Engravers, etc. etc. Now all these bits had to come together at some stage so some type of standard had to have been used or it just would not have happened.
It used to be easy for me as any screws I needed (if I had a sample) it was just take it into work, put it on the shadow graph and measure it, then make one to match. Items with screwed holes in them were a different matter, as most times I had to make a tap to suit them, still have some of them. It is far easier to screw cut a round item than it is to screw cut a hole, purely based on the clearance needed to work in relative to the space required to do it, this is where taps come into there own.

A typical problem is new extractor pins on decappers, their sizes are very odd as are the roll turn-over forming dies to fit an Excel machine. As I make so many of these I actually had taps made to suit but they are not very cheap in fact a set of made to measure H.S.S. ground taps are very expensive and although the mating thread is of Whitworth form in the main they are always oversize on the root radius of the thread and I find it best to run a die down them just to clear out the bottom of the thread.

As John said an interesting subject.

Mike you may be correct it might have been nipples, but he’s the go-too guy.

I wish I could understand at least 1/3rd of what you guys are talking about as about all I can run is a file.

I’m a chemist not a machinIst so I have no clue what you guys are talking about. I do have an old gunsmith book from 1883 that talks about how then “old time” gunsmiths made screws. It’s not very technical (but still confuses me) so probably won’t help much.


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