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MaDeuce
Penny Pincher Member
USA
124 Posts |
Posted - 02/09/2007 : 11:48:01
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Atheist,
I realize that you are doing this at home for fun, but... have you ever looked at how much metal is wasted by the cut of the blade. In other words, how wide is the kerf? An alternative that came to mind would be either water or laser cutting. Probably prohibitive to have it done commercially, but there is starting to be a good bit of activity with these at the home / serious hobbies level. You might find someone that would be wiling to trade some machine time for a few of your rounds. This would have the benefit of making cuts that are flawless, leaving you (I suspect) with a prettier round in the end. For me anyway, making stuff pretty is half the fun. BTW, the ingot and coins above are truly beautiful.
MaDeuce |
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n/a
deleted
479 Posts |
Posted - 02/09/2007 : 12:12:43
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Thank you for taking the time to contribute your thoughts.
I've estimated the "wastage" of the kerf cut / sawdust to be about 12%.
The local copper recycler accepts saw dust.
I have about 6 pounds of clean copper sawdust right now in ziplock bags.
My guess is that 0% of the copper in qwestion is vaporized using my $250. bandsaw.
I assume that if lasers were used, some non-zero qwanity would become airborne.
I do not know if that creates an inhalation health hazard.
I agree that some other method would very likely produce more beautiful planchets
(You must be logged in to see this link.)
But I'm already loosing a considerable amount on this production.
Buying a new machine is not in my budget.
I've noticed that if my feeds and speeds are right, and I use a sharp sawblade, I get a pretty good cut.
If the blade gets hot or dull, then I get an ugly cut.
I've not sold a single slug.
I have given away a couple of hundred.
I've stashed most them for myself.
Lately, I've conclude that buying nickels is a better investment than creating these blanks.
I give them away as conversation pieces to bring out-of-the-box thinking into discussions of whether or not metal is money.
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"Financially, the US economy has degenerated into a sort of cargo cult, where people feel that they can continue to attract recycled petrodollars by dancing around piles of internet servers with their cell phones and their laptops."
-Dmitry Orlov |
Edited by - n/a on 02/09/2007 12:15:20 |
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tmaring
Penny Collector Member
USA
302 Posts |
 Posted - 02/14/2007 : 19:51:31
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Creating slugs.
The way to create round slugs from sheet material without any saw kerf at all is to use a punch press. It works just like a paper hole-punch... except of course everything is much larger and stronger. Two of my screw presses are reserved for blank punching. The best references to this type of work were all written long ago as this is very 19th century in technological level.
It would be difficult in one post to discuss the various parameters of blank cutting. The real trick is figuring out how much force you need so you can size the equipment appropriately. I've made plenty of mistakes. If you underbuild stuff it tears up right away. If you overbuild it you just waste materials.
Basically the process is something like this: First you figure out the diameter and thickness that will yield the weight you want, and either roll out the sheet to that thickness or buy it at the correct gauge. I have a 3hp rolling mill for this purpose. Then you figure your blank layout on the sheet to minimize waste. It's generally best to shear off a piece such that you can punch a double row of blanks in order to make them "tile" the area best. The "die" (hollow part) is set up on the bottom and the "punch" on the ram of the press. Cycle the press by hand in order to align the punch and die exactly, and tighten all holddowns. Since the metal bar will want to stick on the punch, there must be a "stripper" mounted somehow above the lower die, which will serve to strip the bar off the punch on the upstroke. Space the punchings about one metal-thickness or more apart to keep from distorting the edges of the blanks. The blanks will be a bit roundy edged on the bottom side and will probably have a burr on the top side... so most people run them through some sort of abrasive tumbling operation to deburr and polish. You're left with a "web" of waste material that will need to be recycled or remelted. There is a whole science to the exact clearances of the punch and die... (very tight for thin stock, more clearance for thicker stock) but I tend to just use tight tolerances for all and not worry too much about tool life.
I have a page with a virtual tour of my workshop at You must be logged in to see this link. Those photos were done several years ago... so there are some new things that are not shown. The rolling mill is the grey thing at the far right of the panorama shot at the bottom of the page, next to the two blanking screw presses. |
Edited by - tmaring on 02/14/2007 19:56:44 |
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creating copper blanks or slugs
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