Sandcasting larger Lead Weights

Discussion in 'Sand Casting' started by Tops, Nov 27, 2023.

  1. Tops

    Tops Silver Banner Member

    Hello All,
    I was messing around with some designs for lead spline weights (sometimes called drafting whales or ducks depending on the design). They are used to hold flexible battens in position to draw or loft curves in boatbuilding.

    I did 2 match plate patterns 3D printed, drafted except for the bottom as-used which I left flat. The larger was featured in a magazine article and the smaller is me messing around with STL files from Thingiverse under 'rubber duck'.

    I did two open mold patterns by hand from reclaimed cedar and shellac. The block is similar to what can be found in the Herreshoff Maritime Museum and the 'whale' is a classic form that can be found in lead and in bronze. Ideal weight seems to be about 3# (1.4kg)

    I rammed them up in K-Bond, noting that the green strength was failing as the sand cooled from room to garage temperature (70F / 21 to 32 F/ OC) . I had some breakouts that I attempted to repair. I also started with the cope and drag mis-assembled the match plates to the point I had to pull the pins for final assembly (might be fodder for another post...)

    Anyhow, needed 12#, melted 10#, (5.5kg, & 4.5kg) and got the results below. On the big one, the sand collapsed along one of the long undrafted edges.

    The main question I have is whether I could use an aluminum chill to form the flat bottoms (would rather not have to draft then only to remove extra lead to get them to sit flat). Or am I better keeping them as open molds and letting them shrink naturally and file them flat before applying finish and a felt base.

    A second question would be if I found a design that is a winner, could it be done as an aluminum mold so I can skip the sand?


    tops_leadcast1.jpg tops_leadcast2.jpg
  2. Chazza

    Chazza Silver

    Aluminium moulds are used for fishing sinkers; I can't see any reason why not for your application.

    A word of caution: never cool an aluminium mould in water and then pour lead into it. The smallest amount of moisture will cause a steam explosion and some very nasty burns.
    Tops likes this.
  3. HT1

    HT1 Gold Banner Member

    can we discuss this more??? let me clarify Getting patterns 3D printed, Ive had little luck finding someone capable and willing at a reasonable price to do 3D work

    V/r HT1
    P.S. if you cast lead in Sand, it must be rammed TIGHTLY or you may end up with a ball of rat tails and fins
    Tops likes this.
  4. Tops

    Tops Silver Banner Member

    Thanks. I was so focused on getting something cast that I did not re-warm the sand or just start over and re-ram the flasks when the edges got crumbly.

    Yes we can talk about 3D CAD and printing! I'll shoot you a PM.
    HT1 likes this.
  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member


    I've lost foam cast conforming keel ballasts for model boat guys. When I told them to just carve a master from styrofoam and send it to me, they were delighted. But, I used sodium silicate bound sand. Lead is 4x denser than aluminum and that means 4x the head pressure, and 4x the momentum when it impinges on the mold surfaces. It needs to be a bit super heated for lost foam.....not just an outdoor pour but an outdoor melt for sure.

    Tops and HT1 like this.
  6. Ironsides

    Ironsides Silver

    I used to make weights for model trains and the surface was terrible because lead is a lot heavier than most metals.
    Tops and HT1 like this.
  7. Tops

    Tops Silver Banner Member

    Kelly, did you dip the foam before putting it into the bound sand mix? Also wondering if I could make an overgrown 'sinker' mold as lost foam, machining the mating surface and adding alignment pins. That pour would be another one too large for my current setup, more reason for me finishing my 'medium' furnace project or a trip up to Tamarack.

    Melt and pour was outdoors with a cross wind, turkey fryer burner and lead-only cast iron pot. Where aluminum would burn out the K-Bond to gray or black, the lower temp lead only turned it a golden brown.

    I planed and glued a clear piece of knotty pine 3/8" (9mm) thick to the bottom of the whale to get it up into the 3-ish pound (1.5k) range as cast in lead. Carve and sand tomorrow.
  8. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Yes. Like Ironsides said, the finish on sand cast lead is very rough because lead is very good at reproducing detail so it tends to penetrate the sand surface.

    I don't see why not. It'd probably be best to polish the interior features too. The parting line surface should be as flat as possible with generous distance to the mold edge for flashing, and good perimeter clamping. Lead wicks and weeps through cracks like there is no tomorrow. When I salvaged all the lead in the link below, there was an undetectable (until I melted lead) hole in the steel crucible weld. The lead wicked through that hole and ran out the bottom of my furnace.

    As an aside, even though it has such a low melt temp, lead will still alloy with aluminum, but aluminum molds work because they oxidize and the lead freezes quickly so it's not in liquid contact for long. Your weights are a bit chunckier, so they may need riser and remain liquid for longer. I wouldn't skimp on the aluminum mold wall thickness and allow generous cooling between pours so the lead chills.

    If you are going to do much lead casting, I'd set aside some dedicated sand for it and not handle it without gloves. People seem to get overly worked up about handling lead, but like anything else it's level of exposure. When it's molten or superheated it's much higher exposure. I recovered my led from wheel weights which is about the worst source possible becuase there is all kinds of crap in wheel weights that isn't lead (zinc is also common), but I only wanted it for ballast. Still there was some nasty looking oxides and residue in the leftover trash.

    Gettin the Lead Out | The Home Foundry

    Here, are the counterweights for my lifting cart, cast in open face steel mold.

    Tops likes this.
  9. Tops

    Tops Silver Banner Member

    Thanks Kelly. The idea of separate sand for long-term use with lead and a gloved handling procedure makes sense. I have been washing my hands frequently throughout the project.
    This melt was from a SCUBA weight and had very little dross.
    I did about 30# (14kg) of wheel weights back when I was assembling my SCUBA kit. I have a garage nearby whose owner is also a diver who gave me some of his 'stash' to melt.
    The addition to the whale is coming along. I made the mistakes of running the glue out to the edge of the existing whale causing a hard line between the two different woods and then trying to trim off the extra shoe with an old scroll saw, causing dents on the whale's head. Rasps, files, sandpaper, and a little 650 putty to fill in the gaps/cracks/dents. Hopefully I can final sand and shellac tomorrow.
  10. Tops

    Tops Silver Banner Member

    For a given pattern size, is there a minimum of sand to have under and along the pattern? Does metal density affect this?
    The whale is about 4.5" long x 1.5" x 2" tall (115 x 38 x 50mm).

    Above pattern is 3x puttied and sanded and 2x sprayed with shellac. The old cedar takes it in like nobody's business. I decided to coat the bottom with epoxy by mixing up some 5 minute sauce and coating the bottom and then standing it up on top of clear packing tape over a flat backer board. We'll see how it looks/ works tonight after work.
  11. rocco

    rocco Silver

    I'm wondering, is there any type of mold wash that could prevent or significantly reduce lead penetrating the sand?
    Tops likes this.
  12. Tops

    Tops Silver Banner Member

    Epoxy (tinted with green because the tint jar was right there) did well except for a couple skipperdoodles.
    I will let it sit somewhere warm for a while, clean up the edge, and hit the works with some gray primer.
    I got a pine 1x6 to maker some deeper flasks and some 1/8"(3.2mm) brass rod to finish them once I get a handful casted.
    Including a couple pictures of some various finished ones, not my work.
    tops_whale_epoxy1.jpg tops_whale_epoxy2.jpg Spline Edson 4.jpg Spline Edson 5.jpg
  13. HT1

    HT1 Gold Banner Member

    any that harden! so a fireclay /silica wash etc. a graphite wash, wet or dry would not help appreciably, asking about washes, I assume you are using green sand, you dont wash petrobond!
    if you ram HARD, you will not have many rattails until the casting gets larger then I hope you are trying to pour. for instance a single 100 Lb casting, if you are doing many of the same pieces you would be better off to make an alumnim mold and avoid the issues completely

    V/r HT1
  14. Tops

    Tops Silver Banner Member

    I went down a coffee-fueled rabbit-hole, waiting for it to get above freezing to be outside! We started out around 14F (-10C)

    I scanned in the primed whale, messed with the data, and simulated it through the 3D printer and CNC.
    CNC would be the clear winner time-wise (4x faster after correcting for acceleration) but alas I do not have the right cutter on hand. There would be some sanding needed as I did not run a pass crosswise. I could probably make a second wooden one faster by hand than the 3D print. What if I went and got that bandsaw I always wanted...?

    The next real steps would be to locate the next batch of lead (which SCUBA weight or sounder to sacrifice), knock together a 1x6 flask, and ram the current patterns HARD like HT1 advises in a warm environment to keep the sand in good condition.

    PS I suppose I could pour aluminum 'copies' of the master even faster that I could make new wooden ones.

    tops_whale_epoxy8.jpg tops_whale_epoxy3.jpg tops_whale_epoxy4.jpg tops_whale_epoxy5.jpg tops_whale_epoxy6.jpg tops_whale_epoxy7.jpg
  15. Tops

    Tops Silver Banner Member

    I has a casting session today. Turns out the gray primer I used does not play well (dissolves) in #2 mold release wax. Last time I only did the graphite.
    I was once again short on lead, about 2 sprue's worth...making the brick shape lighter than intended.
    I rammed the molds HARD inside wearing nitrile gloves and took them outside just before the pour, cool-down, and shakeout. Outside was 32F/0C.
    I am happy with the bigger whale and the toy duck was whole but with less details than last time. Numbers indicate which session they were cast.
    The bigger match plate with the duckbill had a large shrink on the upper surface as poured. I did not really think about the gating, just a sprue gated to the part, no runners or risers.
    I am thinking of just finishing these out with brass hooks, felt bases, and a coating that keep the lead off fingers and drawings and make more once/if I need them.
    If I were to drag it out, I'd keep making the whale and brick and make the toy duck have a bigger body and base to get closer to 3# (1.4kg) as cast in lead.

  16. Tops

    Tops Silver Banner Member

    Fettled and coated with epoxy. On the bottoms I added a little bit of filler (hollow glass spheres) to the epoxy to fill in the shrink on the parts cast in the open molds. I trimmed the flash off the parts while the epoxy was still green (not sticky but not hard). Again some skippers, I'll probably go after them with 5-minute epoxy and filler before adding the felt, all of that will be after hook install and finish painting.
    FishbonzWV likes this.
  17. Tops

    Tops Silver Banner Member

    The bottoms got filled in a second time and other nicks touched up with more 5 minute epoxy.
    Holes were drilled for 1/8" (3.2mm) brass rod. Bit needs to be retracted and cleaned every 1/8" (3-4mm) depth or it will eventuality bind.
    The two clamps worked pretty good for the drafted shapes in the drill press and soldering. A smaller third clamp could have been added, I did not think of this until afterwards.
    No-clean flux was dripped into holes, rods inserted and heated with torch until solder melted and wicked into hole.
    Epoxy edge on base sanded with Dremel-type sanding tool (mini drum) and rest hand sanded and tacked off with hooks taped off.
    Gray primer, white primer, then color. They are sitting under a heat lamp in the garage so I don't have spray paint fumes in the house.
    tops_whale_epoxy11.jpg tops_whale_epoxy12.jpg
    Tobho Mott likes this.
  18. Tops

    Tops Silver Banner Member

    A sailing/boat-building acquaintance online sent me a picture with dimensions of the ones they used to use in his design office. I am fixing to make one to test for form-fit-function. The piece with Bondo and spot putty is the pattern, the molded lead will be encased in wood once finished.

    dim duck nick woodenboat.jpg nick_weight.jpg nick_weight_test.jpg
  19. Tops

    Tops Silver Banner Member

    I saw these online yesterday. Wondering if I could create something like this with CNC'd lost foam with one of the ducks or whales as a cavity in the middle...

    3416 - 7" x 3" x 2" closed (1" each side)

    After a great season of sports fishing, haven't we all thought we might have stumbled on a new solution for a jig, lure or sinker. Unfortunately the Do-It Corporation cannot produce custom work, so we created the Blank Mold. Your local tool and die or machine shop can create a custom cavity for the Blank Mold based on your design. We recommend getting a quote for this service before ordering your blank mold, as custom machine shop work can be pricier than you'd imagine.

Share This Page