Machining lead......

Discussion in 'Wooden Boat Building and Restoration' started by Roly, Feb 8, 2012.

  1. Roly
    Joined: Jul 2005
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    Location: NZ

    Roly Senior Member

    I have researched this on line but only come up with cnc driven systems with
    no reference to tool bits, rpm, etc.
    What is the low tech method to cut a 180x250x10mm deep rebate in the side of a lead keel?
    My power saw has cut the outline to 10mm deep and I tried chiselling but it is
    really tedious. I was temped to rout it out but was told it would gaul the bit up in no-time flat.
    I guess I could run the stilsaw at 25mm intervals and use a power chisel?
    What about melting it out with the gas axe or lpg torch? Could be a bit hard to control tho'.
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  2. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Lead is soft and easy to cut. Ive used a sharp electric chain saw to shape lead keels. Keep the blade sharp and lube oil pumping. A router also works for small projects. Powerplanes work well on lead

    Your skill saw way is good. Perhaps tack a batten to the keel and keep making cuts and kerf it all away. Clean up wih a router. I used no special router bits and a normal plunge router.

    Ive never tried a blow torch...sounds messy.
  3. DGreenwood
    Joined: Aug 2004
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    DGreenwood Senior Member

    I've run into this solution was to buy one of those $35 air chisels and buy some extra flat blade bits. Sharpen them with a steep edge angle on a grinder. You need plenty of compressed air. (at least 10 CFM)
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  4. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    I cast drafting "ducks" in lead when I was a teenager and had problems drilling the holes for the wire finger. The drill bit tended to grab. Off to visit an elderly but very talented machinist who was a family friend. His solution was to regrind the tip of the drill bit so it was flatter and more scraping more than cutting. Worked great in the lead.
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  5. Nick.K
    Joined: May 2011
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    Nick.K Senior Member

    Try with a router, if possible with a half inch chuck and variable speed on lowest speed. Do it in several passes. Attach a plate to the base of the router if it has a tendency to fall in to the hole. If the keel surface is not flat, attach another plate to the keel to run the router on.
    I have used a lot of lead bar for sash window weights, apart from cutting it to length on a chop saw we would some times run it through the bandsaw for a lighter section. Never had any problems except build up of lead on the teeth that could fly out dangerously. Stop to clear regularly and when you feel vibration.
    Melting it with a torch sounds like a recipe for lead poising from vapour.
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  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Most power tools will gaul, because of the speed at which they spin. Reciprocating tools are less prone to this and if used with a large tooth (low tooth count), they can spit out offending bits, before they can cause issues. Lubrication is necessary and oils are typical, though some still use kerosene, which isn't wise with power tools, but fine on hand tools.

    The lead type (composition) also makes a big difference. If cast with antimony, up to 7%, but typically just a few percent, will make machining much easier.

    Also freezing the lead can help a great deal. Spraying the rabbit line with A/C refrigerant or other really cold stuff, saves the bother of packing your freezer full of ballast casting. You'll need to do this repeatedly along the cut's length (every few feet).

    The basic rules are low RPM, lots of lubrication, a high feed rate with very aggressive tooth patterns. A mutli tool may be useful on this. If you slow down, the bit or tool teeth will clog and gaul in the kerf, if you have too much RPM, the same, ditto high tooth counts and insufficient lubrication.
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