18th c breech threads - HDTDT

[James Wilson Everett]

Guys,

Here are some photos of 18th c gunsmith tools to form the barrel breech threads.  The first photo shows a set of three taps to form a single size of breech threads.  The tools are used in sequence, much like the modern taper, plug, and bottom taps.



Here is the first tool, notice the pilot section to make sure the tap is aligned to the bore.



Here is the second tool to form the first couple of threads and to partially form several more.  Of course, you can see the taper.



Here is the last or bottom tap with parallel sides.  These taps swage or form the threads, they do not cut.  They work well in the very ductile wrought iron.


Here is another larger set from the same bunch of 18th c gunsmith tools.   Notice that the thread pitch is identical to the smaller set.


Jim Everett

[FALout]

Jim, In your last post concerning drill bits, you mentioned a drill plate (I think thats what you called it).  Were these taps run into the plate when red hot?  What kind of steel are these taps, maybe I'm nieve, but if wrought iron wouldn't the taps be brittle for cold forming the threads?

[AeroE]

That's very cool.  Just yesterday I was contemplating whether the old timers used a piloted tap.

It's hard to imagine that many complete sets of three taps remain.

[okieboy]

 Thank you so much for these photos, I have been lucky enough to see a few taps like this, but have never managed to get one for my colection. By the way the shop I work for produces almost all of its holes with forming taps (most of our material is 316L stainless.

[James Wilson Everett]

Guys,

The breech thread taps were made either from blister steel or later cast steel and hardened, or they were made from wrought iron and case hardened.  I don't know which was used for these taps, but I suspect that they are one of the steel products of the 18th c.  They were cold swaged using a split die adjustable screwplate.  With one of these tools the gunsmith can make either tapered or straight threads for the taps.  Also, almost any diameter can be made, notice that the two sets of taps are of different diameters but have identical thread pitch.  This means that the gunsmith used the same split die to make both sets.  The threads are swaged or squeezed into the soft metal, they are not cut.  After the threads are formed there are small cuts along the axis of the tap to give the small amount of clearance for the tiny amount of metal dust resulting from the swage process.

This is a photo of a late 19th c. split die adjustable screwplate.  The one used by our unknown 18th c gunsmith would look slightly different, but the operation of the tool would have been the same as this one.





Jim Everett

[dannybb55]

I have one of these with nominal 3/8 x 16 dies still in it. II have cut a 3/8 mild steel rod with it very easily once. It looks like a Birmingham product.

[Daryl]

Excellent thread - thank you.

[doug]

     That was a terrible pun, Daryl  :>)  :>)      I posted these screw plates quite some time ago but seems appropriate to post in this thread (so to speak) again.   My impression is the the pie knife type were used primarily to hold screws while filing them to length while the large one made by a blacksmith, from a file and the adjustable one were used for swaging threads.

cheers Doug

[James Wilson Everett]

Guys, Doug and everyone,

Thanks for posting the photos of the screw plates.  On the "pie knife" screw plates you can see the paired holes used for making the tap in the slightly larger hole and the screw in the slightly smaller one.  The tiny side holes in the smallest screw plate requires some explanation.  When the gunsmith had the misfortune of breaking off a screw thread in the hole - now what to do?  You can see a couple of these "oops!!" in the largest "pie knife" screw plate.  The tiny side holes allows the gunsmith to insert a jeweler's saw blade into one tiny hole, then to cut across through the broken screw to the other tiny hole.  The two halves are easy to remove after being cut.

Really, these old screw plates are very much easier to use than a modern die, and the threads they make are very smooth and shiney.  Modern dies do a terrible job cutting threads in wrought iron as they cut directly scross the grain of the wrought iron and most often tear the threads. 

Doug - go ahead and make lock screws and taps from these screw plate.  After all - why would anyone wish to have screws exactly like your neighbor - how dull and boring would that be?

Jim Everett

[Acer Saccharum]

Jim, do the screw plates FORM threads or CUT them, or a combination? It makes perfect sense that a cut thread in wrought iron could be weak, with all the fibers being cut.

I never thought about a jeweler's saw for removing broken screws. I assumed those slots were for expansion of the die.

Cool beans, thanks for sharing.

[doug]

    I will have to try to find a jeweler's saw although the screws that are broken off seem to be hardened.  At one point I thought of drilling them out but as I recall they were too hard for that.  I do use the small pie knife one for holding small screws while I file them shorter.

cheers Doug

[greybeard]

Very interesting stuff

[James Wilson Everett]

Guys,

The 18th c. screwplates do not cut the threads, they are formed or swaged.  During the thread swage process there are no metal chips formed.  The threads grow outwards from the blank as they are formed.  For instance, to make a 0.174 - 30 thread I start with a blank of 0.154 - 0.157 diameter to end up with the larger diameter threads.

Jim Everett

[James Wilson Everett]

Guys,

Here is a very interesting item that can easily be used today even with modern taps.  This is a breech tap that dates from the 19th c.  You can tell from the round lathe turned shank that it is of a later date than the prevoius taps.  Notice the nose end of the tap has been cut with teeth.  As the tap is turned into the breech it bottoms out at the breech hole/barrel bore interface shoulder as a normal tap would do.  But here as the tap is turned beyond this point it will actually cut the breech hole deeper.

Have you ever been breeching a barrel and wish for just a little deeper hole - say one more half thread to make the breech plug fit nicely?  Here is the tool old timers used to do that.  I am sure that you can envision how it works.  Your modern bottom tap can be modified in a minute on a bench grinder to give these cutting teeth.  Simply grind a cutting relief angle on each of the four tap flutes.  Now to get the breech hole a little deeper it is easy to use the modified tap - just like great great great grandpa did.

Jim Everett

[Dphariss]

Have you actually tried this tool?
The feed rate of a 18 pitch thread, for example, would be about .055" per revolution.
Based on what I have experienced in tapping barrels it would simply turn in to the inner shoulder and stop after digging in the shoulder somewhat in something like a 45 with a 5/8" plug.
I have a tool I used to use for this but its not a tap and simply fits into the recess and is piloted in the bore. I use this to remove the marks I made in running a tap in too deep and making unsealable divots in the inner shoulder.
Dan

[James Wilson Everett]

Dan,

Yes, the bottom tap with, lets call it lead cutting edges, works just fine.  It is much easier in wrought iron than in modern steel barrels however.  The divots are not so very large and are easily ironed out when the face of the breech plug smashes them down when you really scrunch the plug in tight.  Note the highly technical verbage.  I can tell that you have a deep understanding of the process, thanks for your comment, I do appreciate it!!

Jim

[James Wilson Everett]

Guys,

When you thread the breech using the 18th c type tools shown above the required force is even higher that when using the modern taps.  So, a big wrench is needed to turn the taps in.  Also, of course, you need a very sturdy post vise attached to a massive work bench to hold the barrel.  I often do show-n-tells at 18th c crafts fairs using a portable table that is no where near beefy enough, so I have never demonstrated this.  Here is a photo of a tap wrench that could have been used for this job.  It is not specifically a gunsmith tool, but it is typical of an 18th c big tap wrench.  It is 20 inches long.

Jim Everertt

[James Wilson Everett]

Guys,  Before using these tools to put the threads in the breech end of the barrel, the bore diameter must be opened up to a very specific size and depth for these taps to form the threads.  Note that the 18th c gunsmith did not have access to all of our marvelous modern, electric, carbide tooling, how was this job done?  It does not take too much time to realize that this job could not have been done using a spade bit driven by a brace.  It is nearly impossible to get a spade bit to cut the wrought iron when the bit is so large in diameter (at least for an old little guy like me).  Also, a spade bit will not cut to a controlled finish diameter. 

Here is the tooling that I use.  These are called, in the period, grinders.  They are used in various forms to make a lot of controlled and specific diameters without a lathe.  I use two sizes in my barrel work.  The teeth will cut iron or bronze easily, but not too quickly.  The result is a hole aligned with the bore of a controlled diameter and depth, just perfect for the threading job.  The pilots keep the tool aligned with the bore.  The smaller tool was the second one made and has the improvement of the outer diameter cuts that keep the metal chips from binding.  I use these tools in an 18th c hand brace and can cut the breech hole in about 1/2 hour.

I would really be interested in seeing any 18th c style tooling other gunsmiths use to do this job. 

Jim Everett

[Bob Roller]

This is not a "grinder"by any definition. It is a piloted hollow end mill. A 4 fluted style would do a better and easier job. One thing I learned from Bill Large was how to make cutting tool like this cut.

Bob Roller

[JTR]

I can see that tool being called a 'Grinder' back in the 18th c. Just look at the way coffee or spice grinders were constructed with a similar 'grinding' head.
John

[Bob Roller]

Looking at the "grinder"with the pilot in place,I can't see how it could ever do anything except exhaust the man turning the carpenters brace.
It is rubbing its way thru because there are NO actual cutting angles built into it. Look at an end mill and you will see what I am saying.

Bob Roller

[James Wilson Everett]

Guys,

Thanks for the great responses, its good to see the interest in the old ways of gunmaking.

1.  I don't know why it is called a grinder, but that is what I understand was the 18th c name for these.  Today we would not use the term grinder as it is associated with things like abrasive wheels.  Reminds me of the discussion on this forum on "why do they call them side nails?".

2.  These actually cut quite easily, if slowly.  Screw grinders (which I may show later) cut more quickly as the chips clear from the cutting edges by gravity.  Here the chips are contained in the blind hole and cannot drop clear.  So, you have to pull the tool every few seconds and brush/blow away the chips.  I say chips, but it is actually closer to metal dust.

3.  The cutting edges are there and are sharp enough to draw blood.  They do tend to make the chip bend to a right angle as they are cut from the base metal.  This makes the cutter no where near as agressive as the cutting angles on a modern end mill.  Very often, perhaps almost always, the angles of 18th c metal cutting tools are near a right angle whether the smith was using a screw grinder, breech grinder, barrel facer, cherry, muzzle crown, rifle head, etc.  I really can not think of any 18th c metal cutter that had the modern cutting angle.  Certainly a cutting angle will cut faster and more efficiently.  I guess the first example of such a cutting angle that I can think of is the S. Morse twist drill patented in 1863.  Let me know if anyone knows of earlier examples.

4.  When you drill brass you are better served by modifying the drill cutting edge to near a right angle.  Otherwise the brass will tend to grab the drill bit and pull it through just as the drill pierces the back side of the brass piece.  I am sure that you have experienced this.

Jim Everett

[dannybb55]

 

[Daryl]

tks Jim - what an excellent education in history, we are getting.

[James Wilson Everett]

Guys,

Here is some information from the Journal of Historical Armsmaking Technology, Volume III showing some 18th c engravings of the breech taps and the translation of the original German text.  I hope that it is acceptable to put this info here as full credit is given to that publication.  Here we see the tapered tap and the bottom tap that are similar to the originals shown above.  It is easier to form the threads in three steps rather than the two shown below.  Also, the two handed tap wrench is a lot easier to use and to keep the tap aligned.

Jim Everett