Pinned thread about production technique

[Peter J.]

I was reading through this very interesting pinned thread, but it was closed for replies:

STEP BY STEP FROM A DRAFT TO FINAL IRON CROSS - Excursion in the Deschler&Sohn Munich

On image #2 there's a man working on a magnified 3D model, which I assume is similar to the Ostmedaille seen on the enclosed image i.e. a plaster used for a pantograph.


Then on image #9 a man is working manually with engraving a die. Consequently my question is: why would they need the 3D plaster if the die was engraved by hand?

cheersPeter

[dmytro]

possibly because they used a pantogtaph engraving machine to transfer the pattern to a much smaller metal blank, which then served as a master die

[no1canuck]

What you see in image 2 is the making of a 3D model. The model was wood or another soft material that was made say 4 times larger than the finished product. Being 4x larger lets the craftsman look at the detail so he can make, and correct it easier. Then the wood pattern is placed on one table of the pantograph, the machine ratio is set at 4:1, and a stylus follows the wood pattern while a cutter cuts the die 1/4 the size of the pattern on a second table. The movement of the pantograph is by hand but guided by the stylus on the pattern. What you see in image 9 is the finished die being touched up by hand. It has already been engraved on the pantograph.
I cant tell you how many hours I have spent running a pantograph!!! I still have my Deckel in the back corner of my plant. Haven't used it in 15 or more years. CNC machining has rendered the pantograph obsolete. I have mixed feelings about that as i can run a pantograph just fine but pretty much have to rely on a younger generation for computer programming as i cant get this thick old head to completely grasp CNC no matter how f@#ing hard I try!!!!!

Steve

[Douglas 5]

As the book only shows some the steps in the in the die production .
Quite labor intensive back then compaired to now .

Douglas

[Peter J.]

Steve, thanks for your account of the pantograph. I assume steps have changed over the years (as can be seen in the enclosed link), but the fact remains i.e. why leave out such an important procedure as the use of a pantograph in the article?


https://www.youtube.com/watch?v=VP3Ue_hCBok


I'll take this opportunity to ask a professional about the 4:1 ratio. Was this a fixed measurement or could a different preferred size be set on the pantograph, in order to fit the requirements for the end product?


cheers
Peter

[no1canuck]

Hi Peter

The ratio could be anything that the designer needed from 1:1 up to 10:1 and anything in between.

Steve

[Yubari]

Thank you for sharing Peter. Very interesting video for a non technical person-collector like me.

[Peter J.]

Steve, thanks for the confirmation, that's pretty much what I figured. Would it be safe to conclude the master die (in this case for the beading) was indeed made by a pantograph?


In addition, a maximum ratio of 10:1 by definition rules out any production of dies smaller in size, i.g. for miniatures. Is this a correct assumption or was there any other method to resize the plaster to let's say 90mm?


cheers
Peter

[no1canuck]

Hi Peter

Yes the beading die was engraved by a pantograph.

You could make the soft pattern any size, and then set the machine at any ratio from 1:1 to 10:1 Just for clarity a pantograph is used almost exclusively for reduction.

This means if you start with a 90mm pattern and set a 10:1 ratio on the machine you would end up with a 9mm part. A 4:1 ratio gives you a 22.5mm part from the same 90mm pattern.

Steve

[Peter J.]

Steve, I've no experience in die production whatsoever, the few brain cells I was equipped with from birth is my only instrument for learning. I'll try to explain the reason for my inquiry. Most normal sized badges or decorations, produced with the initial magnified model, all had specific features making it possible for us as collectors to identify a specific producer. This is in many cases also valid for miniatures, even as small as 9mm.


With that said, given the size of the illustrated Ostmedaille model (I venture a guess of appr. 200-250mm), is it really feasible a smaller model (90mm) was produced with the very same specific features found on the larger model? I don't know, perhaps they were that skilled. I did some brainstorming though and like to know whether or not it makes any sense.


What if a mother die for i.g. a PAB was handled in the same way as a magnified model i.e. it was covered with a rubber solution, which then was filled with a plaster and then ready to be used in the pantograph. That 60mm high model would easily produce a 9mm miniature.


cheers
Peter

[Gary B]

Hi Peter,

For background information on die production for coins:

Following an approved design on paper a 3D model of the piece is produced in plaster or some other soft material. The finished model is then reduced to the production sized master hub (positive image) using a reduction or pantograph machine. The hub is then hardened.

This master hub (positive image) is pressed into a piece of metal to produce a master die (negative image). This master die is used to produce working hubs (positive image) which then produce working dies (negative image). Those working dies are used to produce the medals or coins.

The size and intricacy of the piece being struck will determine the frequency in which the dies will need to be replaced. Larger pieces with intricate designs will require more pressure to strike and hence will need to be replaced more frequently than dies used to manufacture smaller items. Eventually if enough working die replacements have to made the working hub will need to be replaced or at least be "touched up".

Gary B

[Norm F]

... which then was filled with a plaster and then ready to be used in the pantograph.

I don't have an answer to the question about precisely how 9 mm mini dies were made that are similar in design to their full-size counterparts, but I have a comment on the use of plaster.

I think plaster is too soft a material to use in the die-engraving pantograph machine. As mentioned in that B.H. Mayer youtube video, first a rubber mould was made from the hand-engraved plaster design as an intermediary step to produce a hard epoxy replica for subsequent use in the reducing machine.

Having said that, I don't know if epoxy existed yet in 1939, so I'm not sure what they were using back then?

Best regards,
---Norm

[Peter J.]

Thanks Gary. This sounds quite plausible, although the account from Mayer gives a different scenario i.e. they skip a few steps and produce a master die (negative) from the model and use it directly for production of the coins. That sounds a bit odd IMO, as a new master die (negative) once being worn out would have to be made in the pantograph, rather than using the working hub you mention.


Norm, you bring forward a legit question, which I don't have the answer for. I did see another video (can't locate it though) and if memory serves me right, I think they used some kind of resin and added a very thin layer of oil with copper dust, which apparently hardened the model. Perhaps some of the EK/KC authors care to add their thoughts


cheers
Peter

[Norm F]

I did see another video (can't locate it though) and if memory serves me right, I think they used some kind of resin and added a very thin layer of oil with copper dust, which apparently hardened the model. Perhaps some of the EK/KC authors care to add their thoughts

That makes a lot of sense. A negative resin mould of the original plaster design, then coated in copper, would nicely fit the bill for subsequent reduction in the die-cutting pantograph machine. The resulting negative steel master die could then be used to make positive hubs from which any number of working dies could be made.

Best regards,
---Norm

[Peter J.]

I don't know Norm, I think this all boils down to the end result of the pantograph. The magnified model was clearly positive and as Gary suggested, so was the master hub. The use of a rubber solution on the model and then the adding of the forementioned mix in that rubber mold, would result in a postive master hub. Without that master hub, a new master die would not be possible to produce without the use of a pantograph.



Why is this of importance? Well, as stated by Gary, occasionally the working die had to be replaced and a new was produced from the working hob. I don't know the life expectancy of a working die (perhaps someone could venture a guess), but using the working hob many times enough to lower its capassity to produce new working dies present a problem. The same thing can be said about master die, eventually that would also lose in quality with excessive use for working hubs. In that sense a positive master hub seems logical IMHO.


cheers
Peter