About Lead?

Something not yet discussed is the lead alloy. Arsenic is added to lead shot to harden it. Antimony was added to lead linotype metal to cause expansion on cooling so that it fully filled the mold. Are either if those going to present a problem? Lead used for roofing flashing is probably fairly pure as it is commonly deformed in use. Plumbers lead may be the same but may be difficult to find since the advent of PVC and ABS pipe. I'm not sure about wheel balancing weights.

In my experience with machining lead, holding the lead was a problem. The cutting tool would grab, causing the lead to deform.
 
Illinoyance said:
I would expect holding the lead in a chuck or collet would be a bigger problem than the turning. Pressure of the jaws will deform the lead causing it to loosen in the chuck.
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This is true; when I wanted a good mechanical fit of lead parts, I'd rough-cut the right size piece, and
squeeze it into a harder-metal frame (like, inserting a bit of lead into a steel washer, and letting the 50 ton
press flatten it). The steel washer can then fit into lathe jaws, for drilling a central hole...
 
I'd cast it into something that I could grip, or just cast to the final shape.

Antimonial Lead is harder than straight lead.

Tungsten is another excellent shielding material anduch less annoying to machine.

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@graham-xrf is trying to make something roughly like this, out of lead. Roughly 2.5" (64mm) in diameter.
leadring.jpg
 
I don't know jack about 3d printing, but if you could 3d print an investment out of the right material (waxes...) it might come out well if sand cast.
 
Weldingrod1 said:
I'd cast it into something that I could grip, or just cast to the final shape.
Antimonial Lead is harder than straight lead.
Tungsten is another excellent shielding material and much less annoying to machine.
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The guys are trying all sorts of tricks. So far, the most novel approach is to 3D-print the shape, but with oversize pockets, to then deform lead sheet into the pockets with a special punch.
--> Pictures here
Regarding why not Tungsten. That happens to be one of the metal we want to get return signals from. It will fluoresce at 59.3KeV, 8;.4KeV, and 9.6KeV. The 67.2KeV is beyond reach because the source has only 59.54KeV available. Lead might deliver 10.5KeV and 12.6KeV as a twin pair, but we know only 2mm of lead will stop 99.99% getting through.

I am thinking the basic shape can be turned on a lathe, on a mandrel, and super glued while squeezed between two washer-like discs.
Stopping it "grabbing" on the tool has been mentioned. My thanks to @WobblyHand for providing the picture.

I am relying on the words of wisdom from MrPete, and the project of another dude who made a turned lead pen. (Yes - I know. That sounds like poisonous in the sweaty hand. It just made me think that this is possible, but I am aware that MrPete's lead was "harder".

Mr Pete's turned flywheel stuff is here.

Nathan Cumming's toxic pen is here..
 
pontiac428 said:
I don't know jack about 3d printing, but if you could 3d print an investment out of the right material (waxes...) it might come out well if sand cast.
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That's what I have been thinking. I printed the above, but in PETG. I have yet to find a wax that would work, but have to think if fired at high enough temperature, the plastic would burn out.

Edit: I found 3 filaments that are for lost wax, got to check pricing...
 
WobblyHand said:
That's what I have been thinking. I printed the above, but in PETG. I have yet to find a wax that would work, but have to think if fired at high enough temperature, the plastic would burn out.
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Is that the way where you 3D-print the shape, then repeatedly dunk it in plaster slurry, drying out a bit between each dunking?

If that shape is given sprue funnels, and a outlet, and fired to first dry out without cracking, and then taken up to red heat, the plastic should burn out of it just like wax. Polythene is just polymerized candle wax. If one can make jet engine blades this way, then it seems possible to make a mold for lead.
 
graham-xrf said:
Is that the way where you 3D-print the shape, then repeatedly dunk it in plaster slurry, drying out a bit between each dunking?

If that shape is given sprue funnels, and a outlet, and fired to first dry out without cracking, and then taken up to red heat, the plastic should burn out of it just like wax. Polythene is just polymerized candle wax. If one can make jet engine blades this way, then it seems possible to make a mold for lead.
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Basically yes.

There are special filaments which are guaranteed to burn out with low ash. I found three sources and priced two of them. The cheapest I found is $49.99/kg spool. And yes, I would design in the sprue and vent hole and print that as well. I don't have a kiln though, and you need to bring the filament up to 750F minimum to guarantee ash free burn out. The filament makers claim melt out is insufficient for a good cast.
 
Sounds pretty good for a benchtop endeavor. Lead is so well-mannered when you pour it, seems better than trying to machine it.
 
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