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Gravity drop hammer coining machine

garyd

Aluminum
Joined
Sep 29, 2004
Location
Connecticut
Hello Gents;

Back in the ole’ days, way before hydraulics provided a better solution for folks making medallions, jewelry and struck coins, folks used either very large (and very heavy) knuckle presses or gravity drop hammers for the smaller work.

Any chance that one of us has a Blundell & Co. gravity drop hammer coining machine or a functional equivalent who would be willing to correspond with me so that I may learn about the capabilities of these old machines? I’m looking into coining small medallions. A hydraulic option that I’ve tried won’t work to my satisfaction (100 tons). The drop hammer machine looks build-able and would fit into my small shop.

I’d like to get a better understanding of the structure of these antiques, the methods employed to manage the falling weight and an idea of the practical limits of these machines. I’ve calculated the kinetic energy of a falling weight accelerated by gravity and the potential for work is amazing. The pic below is of a Blundell machine removed from service after more than 100 years.

Gary

blundell.jpg
 
Gary'
I dont have the info you're after, but, you might also want to consider a tredle hammer. (also known as as Oliver hamer in deferance to the early patent holder.)

Phil
 
I have two different directions for you to go talk to people in-

First, for coining, there is a guy who makes all kinds of amazing coins and medallions-

http://www.shirepost.com/index.html

I dont think he uses any drop hammers- but you can see and read about what he does use, and why, on his website.
I would imagine he would be willing to discuss your press with you.

Then, there is a company in Nevada Missouri that still uses a whole shop full of big drop presses, most quite large, to manufacture metal ceiling panels and all kinds of other sheet metal ornaments for the historical reproduction building trades.

http://www.wfnorman.com/

Call em both up and pick their brains.

My guess is that some other varieties of press are better for coining than drop hammers, which seem best suited to thin sheet forming. But I could well be wrong. Its happened before- daily, if you ask my 12 year old.
 
I have an old 1938 book here called 'the plastic working of metals' It has a chapter on Coining. I should be able to dig it out.

What did you try to do that wasn't satisfactory? Copper? Sterling silver? Gold?
 
Thanks for the replys gents.

I've spent the last few months searching the net and have found numerous resources for my needs. I believe that I've found most things find-able. The tool and die making part of this is not an issue.

I built a 100 ton hydraulic press to accommodate my coining dies. It'l work fine with pewter but I prefer to use nickel silver for certain of my parts. The hydraulic setup just starts moving metal and really does not fill the dies. Brass is not quite as bad but still not acceptable. I've tried a bronze alloy that got better. I'd like to get crisper details. The medallion is 3/4 inch diameter.

I have space issues in my shop. Even if I could find a suitable mechanical knuckle press I could not even get it into the building. A surplus 250 ton hydraulic coining press would be great but its way out of budget. Same access problem. The calc's tell me that I can make this part (and the others I am planning) with the press pictured above given a 100 pound weight and 48 inches of drop. I have a several decent pics that provide sufficient info to permit me to layout drawings for the structure and have done so. What I lack is the practical experience of weight control and press capability mentioned above. I'd like to find some experienced views before begining to cut metal and constructing.

Gary
 
I was surprised to see how small a 250 metric ton hydraulic coining press is. Just a 51 x 28 inch footprint and 60 inches high. But it weighs 2500 pounds. Gold machinery has some other coining presses, and is not very far from you. The Hi-Ton 250 ton presses are under 200 pounds. Search their site for coining.

Gold Machinery, Pawtucket, RI - 250T coining press

On edit: I see your drop hammer picture was lifted from the Gold Machinery site, so you know about them. I did not delete my reply, thinking others may enjoy looking at the link to Gold. The Antiques section is worth exploring, guys.

Larry
 
I still say you ought to talk to Tom Maringer at ShirePost first- he has been actually making coins, and selling em, for 15 or 20 years now, and he knows of what he speaks.
He uses a 320 ton press for his larger coins.
I have not done the calcs, but I sure dont see how a 100lb weight dropped 48" can come anywhere near the force of a 320 ton press.
 
I have made a couple of simple dies and planed to use them originally with a drop hammer but built a 250 ton hydraulic press instead because it seemed more versital. I tried to do coining with less pressure under 100 tons and had the same problems you are having I think you need about 150 tons to get resonable detail. I still want to build a drop hammer because they look like a lot of fun I even thought about doing one with a hollow hammer head and filling it with lead so it could be like a dead blow hammer.
 
Tom Maringer is a fine fellow. We've had a number of chats since September and he's been instrumental in helping me get my tooling act in order.

I have to adjust my parts design to accommodate what process and equipment I can come up with to fit into my basement shop. Even if someone gave me a commercial coining press I could not use it for these constraints. My 14 inch Hendy had to be taken down to pieces to get it in as well as most everything else. I've got 14 pieces of machinery here now. It's tight.

I understand that with drop hammer equipment deployed for this application the major concern is in managing the mass immediately after it strikes. There is a rebound (and restrike) that can effect the work detrimentally. I have not yet been able to deduce how this was managed on the equipment pics I have seen. It may be that I'll have to observe the performance of the weight before understanding this better. Hence, my original request.

I have seen video of similar gear used by moneyer reenacters at renaissance fairs for the same purpose. The restrike is obvious. The solution will probably be simple, the hard part is figuring it out.
 
I have a hammer very similar to that. The biggest difference that I can see is that mine has a a solid cast iron base. The ram on mine weighs about 50 pounds. When I first got it, I didn't know that the proper way to run them was with your foot and leg - holding the ram up with your foot flat on the floor and then quickly lifting your leg to allow the ram to drop. That method probably has sufficient control to strike a coin or medallion. I set mine up with just a rope that you pull and let go of. It works okay but the ram almost always bounces which is not something you want when striking a coin. I bought it for upsetting hot stuff but it is really to small and I need another 450 pounds of ram or so. I saw one like you have pictured in operation at a local silversmithing operation. They were using it to make the bowls of handforged silver spoons. The ram had a convex die and the bottom die was a cast piece of lead. They had a flask set up on the hammer base and would pour molten lead in and then carefully lower the ram into it to make the cancave part. These guys also had the hammer I needed but it was just a bit much for me at the time. I believe it was a board drop and was a couple of stories tall. I had no place to put it and I don't think the neighbors would have liked it much either.
 
yup. I understand that these hammers were equipted with some sort of toggling-weighted-lever that would actuated upon the passage of the weight, and stop or actually hold up the weight after it hit and slightly rebounded off the tools. I have seen safety latches or levers fixed to the tie rods apparently intended to hold the weight out of the way during setups. No details yet on the rebound management devices.
 
btw, you can easily double or triple your force with a lever in your die, hard to describe how to do it, but basically adding a short lever and fulcrem in the die for the hyd press to puch against. you only need a short action area and the hyd press has a long one with constant force so this works with hyd s but not mechanicals.
 
john;

I thought of that. Sketched a few ideas but concluded that I could not get sufficient section around pivot pins to survive the force. My fabricated 100 ton press has only 8 inches of daylight. Do you have any pics of this having been done?
 
Don't know if you have any Renaissance Festivals in your area. There is usually a fellow there with just that type of hammer. His story is that Lenardo DiVince was the originator of this process. The weight is dropped from different hights to coin the different types of metal. This fellow was coining silver, gold & bronze. The hammer itself appeared to be a slug of steel about 6-7 inches in diameter by 10 or so inches long. I can't remember what the die holders looked like. I would think a simple rebound cushion could be a urathane donut. The definition in his coins were very good to excellent. Try googling for the location of these festivals to see if you are close to one. cdw
 
Gerrit;
Super film on the use of the drop hammer in jewelry making. The whole site has interesting production equipment demonstrated. Thanks
 
garyd
to double your 100 ton press capacity, you would need to resist 200 at the fulcrem. but that is still only 100 on each side of th fulcrem, so a 1 1/2 inch high grade shoulder bolt will do that. the fulcrem housing could be 1 1/2 in thick crs. attached to your die base or press frame. These are seat of the pants numbers. I had a 12 ton press that needed to to a 20 ton embossing job, arranged it this way and it worked very nicely, but that was only 20 tons
 
In my miniature field I doe some forming (not coining) and I found that hydraulic forming works for deep forming but you need a sharp jolt to detail form. I use both. I deep form the part in a press and then move the die and part to a little home made punch frame and give it a good jolt with a dead blow hammer for the crisp detail. I think hydraulic would not have enough quick jolt force to give a crisp impression on a coin with out some form of quick jolt to set it.

Maybe a hydraulic ram could be combined with a drop hammer and not need as large of hammer.

Bill
 
I wonder about your use of nickle silver... not doubting your requirement - you know best there, just your desire to obtain the same detailed finish as if you used softer metals.

Compared to gold and silver, N-S does not "flow" under pressure with the same ease as these named materials thus more difficulty in completely filling in the smaller details in dies.

You may wish to review your material. Of course, the ratio of the copper, nickle and zinc changes both the appearance and the ability to "flow."

Regardless, much luck to you!

Stan Db

The following is from the web:

There are many different formulations of alloys which fall within the general term of "Nickel Silver". All contain copper, nickel and zinc, while some formulations may additionally include antimony, tin, lead or cadmium. A representative industrial formulation (Alloy No.752) is 65% copper, 18% nickel, 17% zinc. In metallurgical science, such alloys would be more properly termed nickel brass.

Some nickel silver alloys, especially those containing high proportions of zinc, are stainless.

Nickel-silver alloys are commonly named by listing their percentages of copper and nickel, thus "Nickel Silver 55-18" would contain 55% copper, 18% nickel, and 27% other elements, most probably entirely zinc. A two-element alloy may be named for its nickel content alone, thus NS-12 is 88% copper and 12% nickel.
 








 
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