I can only think that the cut-outs in the die are some sort of fine adjustment to top surface either to correct for distortion caused by hardening the part or maybe slightly modify the thickness of the part being pressed.

I could be completely wrong, but I can't think of any other purpose as the recess in the mating part seems to be flat bottomed.

It's an interesting question.

Neil

Thanks Mike for the drawing. I'm not sure of the tensile strength of the silver you are using, but based on previous jobs I have worked on with silver alloys used in electrical contacts, I estimate the bend force per 48 mm long bend to be a few hundred pounds max. I think mild steel would be fine for the dies unless you plan to run millions and millions of the parts. If you use higher strength material rather than silver, or plan to run huge qty's, use gauge plate. Just my opinion.

PS- to your question 2 about re "cutouts" – if you are referring to the two holes at the inner ends of the thin slots, they're probably done as a crack prevention strategy and possibly as a sawing blade relief at end of cuts.

Makes sense to me, except maybe the other way round. I imagine the springs spread the pressure out from the centre towards the ends. The middle of the silver bends first, and the spring action causes slightly less force to be applied at the ends. It would make the die less likely to damage the ends.

Dave

I can help, perhaps, from my own experience as a silversmith apprentice. To make sharp corners in a silver box, I cut a groove along the line of the desired bend. The tool was made from a bar of silver steel, heated red and turned over at the end. then filed so that it cut a 90 degree slot when pulled along. And then hardened and stoned to the exact shape. A thick steel rule was clamped firmly to the flat plate, and the tool drawn along by hand several times, to remove about 2/3 of the thickness, along the length of the fold required. The same operation was then done for the other folds in that workpiece. Two parallel grooves, and two more at 90 degrees, gives the base and four sides of a box – and four off-cuts in the corners. These latter pieces were carefully removed and the edges filed smooth at the correct angle. Then the sides were folded up to bring the edges together, and propped on a heatproof slab with the sides held firmly together. Borax flux was then applied, and the joints were silver-soldered to give a smooth, rounded run of solder down each side and along each of the base edges. this resulted in the outer edges of the bottom being sharper than could be achieved by bending, and with no chance of roughness as the thinner metal was indeed bent rather than soldered, on the outside. At the same time, filling the join with solder made it much stronger (firmer) than a simple bend.

For your purposes, the tool (and the grooves) should be made sharper (say 40 or 60 degrees, not 90) to suit the geometry of your bend. But remember that if you need the result to have the stiffness of hard-rolled metal, this process might not be ideal as the soldering will surely anneal it.

I hope this offers a way forward

Cheers, Tim

You will get more precision if you use a small fly press with tooling to fit it. The trouble with trying to get bends is the springback that varies with every metal alloy. The most stable results are to bend slightly past the design angle and then use minimum force to bring the bend back to optimum. I did a lot of straightening of part machined aircraft components part way through their manufacture and there was always some springback to take into account. I kept a book with the "recipies" for parts as once the first had been successfully finished, the others took 1/10 of the time and this also worked for future batches.