Making a Die

I would like to reproduce a small fuse cover that was used on some Auto Lite generators. It would be a small run, say 20 or so. They would be soft brass .025 .

Is it possible to use a two part plastic product to make both halves of the die? Anyone been down this road ?

I don't think the die would be able to handle the forces of forming the corners of the brass cover. If you made your brass blanks with cut corners, so the die was only folding the sides down, then it might hold up. You'd have to solder the corners of the cover, probably NOT what you want.

I'd think the you could make a die from aluminum, and with proper lube on it for the actual forming process, it should hold up for a run of 30 or so covers..

If it's not a lot of work, I'd still try the plastic products. If you enclose the outside of the female die tightly in a strong form, it might work, but I'm thinking it will split or the male portion will crumble at the corners.

Make sure the brass is soft, not work hardened any, anneal it first to be sure.

I'd like to know if your plastic die will work, looking forward to your feedback.

GLong

What gave me the idea, is this two part fiberglass die that I purchased about 10 years ago. It had some miles on it then. I have formed at least 20 steel panels using it. There is a crude angle iron reinforcement that we use to preserve the die as much as possible. The the chrome plated steel is .030

Just this week, I had a temporary bridge installed at the dentist. I asked what kind of material he used. He didn't know what the chemical name is but it is a two part epoxy.

If you can take a little thicker wall, then investment cast parts might be an alternative. Trying to deep draw the parts from brass sheet without tearing the corners will take a little time and good die work - OK if you are planning on a few thousand parts but not for just 20.

Have you thought of making the part out of plastic, if you can find a plastic sheet that can be formed but will stand up to the heat of the engine compartment?

I am sure there is some way to do this, whether it would be cheaper than making dies for forming metal I don't know.

That's a fairly deep draw. Likely done progressively in two or more draws. It can easily be done, but not cost effectively............Bob

I think as GLong suggested pre-cutting the corners and soldering them later would be a good idea.

Could this cover be cast using low melting alloys from rotometals or cerro alloys? Make the casting halves in Plaster of Paris which should hold up for 5-10 castings. If you still want to make a die, Kirksite??

The cover needs to be flexible enough to snap over two prongs that are affixed to the top of the generator.

If I was going to duplicate the part, I would put some JB weld in the part with some mold release and then let it harden. That would be the die.

Then I would get one of these http://www.samstoybox.com/toys/Vac-U-Form.html A Mattell Vacuform and make as many as you would like.

You can buy the plastic sheets on ebay and the unit also.

http://www.ebay.com/sch/i.html?_odkw=vacuform&_from=R40&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R1.TR2.TRC1.A0.H0.Xvacuform+mattel.TRS0&_nkw=mattel+vacuform&_sacat=0

IMO, easy.

You could make the part with fiberglass. If it's painted, no one would know.

Phil

These little covers will be sold to Auburn Owners that are missing them, which means they have to make them as accurately as possible.

I have decided to make a steel die. I'll post pix as the project progresses.

Some small parts can be made using a male die only with a block of very hard rubber being used as the female die.

I had to make a crank hole cover for my Studebaker Indy car replica, so I hydroformed the part from thin brass sheet, as Restorer32 suggests above. It has two raised semicircular grooves. I machined an aluminum plate with the grooves as concave surfaces, then bought some thin brass sheet and some thick, hard urethane pads. The aluminum die was placed inside a 4 inch steel tube, then a brass disk was loaded with a urethane pad and a thick steel "pusher" on top. The assembly was placed in my hydraulic press at maximum pressure. The urethane behaves like hydraulic fluid at these pressures and forced the brass into the shape of the die.

My 12 ton press was a little small for doing a 3"-4" diameter part, but a 12-20 ton press might be OK for something as small as your cover, 30-50 tons is better for getting the fine details. McMaster Carr and MSC carry urethane pads in various durometers. Try some in the 60-90 range. I think the pad thickness needs to be about twice the depth of the part. Even hydroforming the part, it will still be difficult to get the sides and corners wrinkle-free. Leave the protective plastic sheet on the brass when forming to prevent scratches.

Traditional deep draw processes have an upper die in two parts: The outer frame clamps the flat sheet tightly to the lower draw ring (hole), then the male die pushes the sheet into the opening and down. I've had parts made this way up to 12" diameter and 8-10" deep from 0.135" thick stainless steel, but the dies and press were massive. The clamping action prevents too much metal from slipping into the hole and forces the stretching action in what does get pushed in. The side walls will get thin and may tear, so difficult draws are made in two steps: first a small draw in the reverse direction, then the part is flipped and the full size draw is done by pushing the small dimple into the draw ring and continuing down. With the right clearance between the male die and draw ring, the wrinkles get "ironed out", but that's what good tool and die makers get paid for - and I'm not one of those.

Good luck on this project!

Nice work, Gary...................Bob

This is really good information Gary, Thank You!

I had to make a crank hole cover for my Studebaker Indy car replica, so I hydroformed the part from thin brass sheet, as Restorer32 suggests above. It has two raised semicircular grooves. I machined an aluminum plate with the grooves as concave surfaces, then bought some thin brass sheet and some thick, hard urethane pads. The aluminum die was placed inside a 4 inch steel tube, then a brass disk was loaded with a urethane pad and a thick steel "pusher" on top. The assembly was placed in my hydraulic press at maximum pressure. The urethane behaves like hydraulic fluid at these pressures and forced the brass into the shape of the die.

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My 12 ton press was a little small for doing a 3"-4" diameter part, but a 12-20 ton press might be OK for something as small as your cover, 30-50 tons is better for getting the fine details. McMaster Carr and MSC carry urethane pads in various durometers. Try some in the 60-90 range. I think the pad thickness needs to be about twice the depth of the part. Even hydroforming the part, it will still be difficult to get the sides and corners wrinkle-free. Leave the protective plastic sheet on the brass when forming to prevent scratches.

Traditional deep draw processes have an upper die in two parts: The outer frame clamps the flat sheet tightly to the lower draw ring (hole), then the male die pushes the sheet into the opening and down. I've had parts made this way up to 12" diameter and 8-10" deep from 0.135" thick stainless steel, but the dies and press were massive. The clamping action prevents too much metal from slipping into the hole and forces the stretching action in what does get pushed in. The side walls will get thin and may tear, so difficult draws are made in two steps: first a small draw in the reverse direction, then the part is flipped and the full size draw is done by pushing the small dimple into the draw ring and continuing down. With the right clearance between the male die and draw ring, the wrinkles get "ironed out", but that's what good tool and die makers get paid for - and I'm not one of those.

Good luck on this project!

Very innovative. Thanks for the details.

Here's another technique I learned at Kent White's "Tin Man Tech" classes. He had a female die machined into a steel block with a frame to clamp a steel or aluminum sheet. A pneumatic rivet gun with a shaping head was used to "flow form" the sheet into the die. Kent had a large selection of heads with different shapes, some made from steel and some with plastic tips of various durometer hardness. He also showed us some other dies made from oak or other hard wood. In the pictures below, you can see a sheet being annealed before forming, then one of the students using the rivet gun to shape the part. The edges get trimmed later. If you are skillful and patient, you can do this by hand. A square corner will still be very difficult. See www.tinmantech.com. The classes were a great experience!

I had a friend make a die. There were a couple of failures in the beginning, as the corners did tear. This works OK for a small run. The material is copper plated steel .020 .

Looks like a good solution, nice die! Is the material actually copper sheet roll-bonded to both sides of 430 stainless steel? There is some material called CopperPlus used for high-end roofing, gutters, etc. made that way. Your parts look like they can be easily soldered at the corners.

Gary, the steel is very magnetic. I did have to solder the inside corners of the first few until I got the size of the legs down. It is still not perfected as I am going to have the die slightly modified.

Yes, the CopperPlus material has a middle layer of type 430 stainless steel (16-18% chrome, no nickel) and is always magnetic. This is the grade of soft stainless steel used for architectural and automotive trim and many other thin, stamped parts.

Also, remember that "better is the enemy of good enough!"

[i should talk, having been sucked into projects without end way too many times, LOL!]

I learn something new every day!

Why use that particular material? Does the copper slide more easily into the die than steel would?

Make sure the steel the cover clips onto on the generator is well protected from corrosion, with the copper on the cover.

Initially I thought it was solid copper and was under the assumption it would form better. Then when I went to grind off the flashing I found out it was steel.

Another reason I used it initially is it is something I had in stock. IE no money outlay. Gary Ash indicates it is a good material, so I am going forward with it.

I was wondering about the plated material too. If you used a solid material (copper, brass or steel) you could anneal it and that might help form without cracking the corners. I would be concerned that if you tried to heat your material to anneal it, the plating might flake off.