Making Headstamp Bunters


#1

Is anyone familiar with the details of making headstamp bunters BEFORE the current method of using EDM (Electric Discharge Machining).

It is my understanding, which may be completely wrong, that the method was as follows.

  1. A softened steel Master Die was engraved with the letters protruding and in a mirror orientation. After engraving, the Master Die is then hardened.

  2. Several Hobbing Bunters were then made from the Master Die. These would have depressed letters in normal orientation.

  3. Finally, Working Bunters by the 100’s were made from
    the Hobbing Bunters. These have protruding letters in mirror orientation, like the original Master.

  4. the Working Bunters produce the headstamp as we know it.

Assuming the above method is essentially correct, my question is, when making the Master Die, how are the letters actually made. Do they use a Leroy Lettering Tool, some kind of Pantograph device, or what? It is obvious that the letters are TOO regular to be hand engraved without some sort of guide.


#2

Headstamp Bunters are just a specialised type of "letter & number " stamps used by the engineering trades (and Gunsmiths in particular).

As you described, the process is correct, with some variations. Bunters could(and were) made up in segments, so that worn or chipped parts could be replaced, rather than discarding an entire bunter for a small chip in one part of it. The Master-Hob-Bunter system is also correct.
Original Masters were done with fine burring tools using a reduction 3-D pantograph from an enlarged (overscale) pattern, much as 2-D pantograph Number engravers are used by the Shopping-center Engraver.

The World’s foremost maker of Engineering pantographs (for Toolmaking, die sinking etc) is Deckel of Nuremberg ( also made Maxim Locks during WW I for the MG-08). Their tri-axis (x, y & z) engineering pantograph tables are still the “Rolls Royce” of the Toolroom for such work.

The primary use of such pantographs these days is hand preparation of complex injection moulding dies, such as Plastic Model Aircfraft kits and Railroad Modelling rolling stock etc ; or small production runs (CNC machining centres have taken over the large production runs of such work).

US headstamp Bunters, being simple “date” & “factory ID” at 120 degrees, 180 degrees, or sometimes a five position layout (72 degrees) allowed for single Bunters to be made, combined with a final primer Pocket " sizing" button, to ensure concentricity of the headstamp with the head of the case…
During WW I, numerous British .303 manufacturers, because of separate Pocketing and head-bunting operations, has “offset” headstamps, sometimes running off the edge of the case rim.

US Bunters were also “recycled” in both 1944 ( 3 cancelled by grinding off a 43 bunter) and 1955 ( 3 or 4 ground off any of the 53 and 54 bunters) leaving a lopsided single “4” or “5” on the headstamp.

Multi-lettered and numbered headstamps in European (ie German) headstamps, with a variety of Lot numbers, Month numbers, segments, metal coating types, etc, could afford a solid bunter in peacetime, but the exigencies of war brought about the development of the Segmented Bunter
(like a ring of individual stamps, made on a segmental pattern, like the segments of a Turret lathe bar chuck.)
Taking the figure of about 180,000 for a Patrone 7,9 Lot in Germany (Kent)
it would simply be wasteful to throw away solid Bunters at the end of a lot, when by simply changing the lot number segment, the bunter can be used to the full economic extent of the crispness of the stamps.

Since Bunters are “pressed” in, NOT hammered, there is less chipping of the edges of the letter/numbers etc, which normally happens in tradesmen’s hand held(and hand hammered) stamps.

The Modern process of electro-erosion is complicated in its own way…the eroding carbon electrode also has to be a perfect mirror of the part to be eroded…and this has to be done by a pantograph as well (whether CNC or by a craftsman’s hand) so the only advantage is there is no “pressing of stock” into a hardend Hob, and all the work is speeded Up, somewhat.
Electro-erosion also gives a finer surface finish to the end product, which in the old days required a lot of hand polishing. Both methods are overall, time consuming.

The economy of Bunter making depends on the complexity of the headstamp. A simple Logo at 12 o’clock with a calibre designation at 6 o’clock can be the subject of a 50/50 segented bunter, if the same logo can be used with several calibres or dates…Logo or ID segments can be made in numbers, then mated with a lesser quantity of date or calibre stamps as the lot sizes require.
Large calibre shells (over .50BMG) are often the users of segmented bunters, given the large size and separation of the individual letters and Numbers.

All these notes above are relative to “Impressed” headstamps; Relief headstamps (where the letters stand proud of the head surface (such as 7,62x54R and larger Russian shellcases, or the combined groove and raised headstamp of the 6,5 and 7,35 Italian cartridges ( also 8x59Breda), these require a solid HS Bunter, as the bunter also imparts another structural feature to the case head (the bevel of the rim in the 7,62x54R, and the head re-inforcing groove/primer seal in the Italian cases. Since Russian and Italian cartridges didn’t carry ephemeral lot numbers or other variable details, a single bunter design would do for a whole year’s production, needing only sufficent bunters to economically stamp all the production foreseen for the year in question. In Italy, the change of Inspectors Initials due to factory administration was a problem, but changes were usually foreseen, and job tenure was assured, barring accidents or foulplay.
Also, relief bunters are easier to make than impression bunters.

In general practice, the abandonment of “serif” letters and numbers for Square Block letters also assisted the economies of Bunter production (mostly this occurred during or immediately after WW I).

Hope this adds to the sum of knowledge regarding headstamp design.
(I am getting Forensic here, as headstamp characteristics are like Forensic Typewriter identification, and similar related areas of the Forensic sciences)

Regards, and Happy New Year,
Doc AV
AV Ballistics Forensic Services


#3

Think these cartridges were a part of the


#4

Doc AV–What a great description of the bunter making process. Thank you.

Now for the reason behind my original question. My son is a Master Machinist and works a lot with EDM and Computer Controlled Lathes and Milling machines. However, he has very little experience as a tool and die maker. He and I got into a discussion about Remingtons change in the length of the dash between the R and P from 0.040 inches long to 0.015 inches in 1971. I asked him, from a machinist and production point of view, could he see any reason for the change, since on the surface of it there seems to be no obvious reason. He suggested that perhaps Remington could no longer get the engraving tool in the size they had been using and the new tool required more space to work between the R and P or maybe the people making the Master Dies suggested it would make their life easier if a shorter dash was used for some reason.

To explore these theories, and perhaps others, I needed a fuller, more detailed explanation of the process of making the Master Dies.

Does anyone have any information or speculation about the reason for the change?


#5

Back in the early 80’s I TIG welded ''repairs" to the number/letters on bunters for the battery industry. Chips, worn an missing segments were built up larger than the origionals. I was told that they were remachined in CNC mills using the origional programs.


#6

Ron,
Can you flesh out your question more. Maybe I am missing it… but are you talking about just the R dash P ammo from Brdigeport or the witch to R dot P when Lonoke started production at that same time frame?


#7

Chris–For some time a lot of us thought the short dash and the dot were the same. But when a Remington drawing came to light (published here on the Forum back in about February) and re-published below, it became clear that they were different and the “Short Dash” (0.015 inch) was an intentional change by Remington from the “Long Dash” (0.040 inch) to all of it’s Bridgeport production.

The Long Dash had been authorized 14 Apr 1960. The revision to the short dash is dated 30 Dec. 1970. This is BEFORE production started at Lonoke. If I remember correctly, Lonoke started production late 1971 or early 1972.