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Labeling Your Weights - How Do You Decide

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When I design a lead mold often do a 3D CAD drawing and then just click "calculate volume" to get the displacement.  If its get hardware inserted in the casting I'll model those and subtract it from the CAD model first.  Atleast if its significant.  Then I just do the math to convert from volume to weight.  

 

I have a small stock of lead for modeling, and I test every mold before I send it out.  My test pieces are usually a smidgen lighter than the model.  This is to be expected as pretty much all salvage lead has some tin, antimony, alloyed in.  Recently I did a mold for a guy, and all of his pieces were consistently lighter than my test pieces.  Then I found he had a huge percentage of tin in his lead.  

 

As a result of these variances its hard to say what weight a mold will produce, and even if you are dead on with say 95/5 when somebody casts some 60/40 it will be different.  

 

I am sure that most mold size labels are an approximation as a result.  So how do you decide what weight to call your finished baits?  Do you even check them?  

 

No major point really.  Just curious.  I have noticed that one spinner bait company listed most of their baits at in between seeming sizes.  3/16, 9/16, etc.  I wonder if they did that as a result of the anomalies I mentioned.  

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Bob,

   I have pondered over this for awhile. I have designed aluminum jig molds for guys, and I do the same you do. Once I come up with a size in ounces, I do that using pure 99% lead. Once it is calculated for that, I'm done. Pure lead is the heaviest. If guys mix antimony in their lead well not much I can do about it. This is a no win situation, because if you cut your mold for pure lead, and the guy uses lead with an antimony mix (% unknown), then his baits naturally will be light. If the guy tells you that his jigs are light tell him that it was figured for pure lead. If he used a lead mix, that is not your problem. The other thing on this is that you don't know where guys buy their lead from. Every place could be different. With that said, cut to the pure lead, stamp your mold and call it a day. Even Do-It sand cast molds do not weigh exactly what is stamped on the mold, and that is with pure lead in it.

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Well as you know Bob most of my stuff is weighed in ounces not portions of an ounce.

So for me if a jig weighs 3.9 oz or 4.1 oz or dead nuts 4 oz it's not that big of a deal. Also with my vertical jigs the assist rigging and hooks will also add some weight. Powder paint adds just a bit of weight as well.

But I think you need to design the molds for 99.9% pure and go from there. Like Cadman said you can't control their alloy.

Also what happens when they use a different hook that is thicker or thinner? Again out of your control.

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