Casting Machinable Wax: Oops!

Remelted machinable wax

Remelted machinable wax

I put a new bag in the vacuum cleaner while machining the prototype case for the bike radio adapters, which was a Good Thing: the swarf from those two halves filled the entire bag!

I gutted the bag and dumped the swarf in a pot to melt down for another use. It started as a brick, but I figured having some rounds might come in handy. A bit of rummaging turned up some pill bottles of just about the right size.

Unfortunately, I didn’t think quite far enough ahead: notice the shoulder around the right-hand end of the shorter cylinder? Yeah, the bottom of the bottle was bigger than the top…

Fortunately, I don’t have a deep emotional attachment to the bottles, so carving it off the wax wasn’t a traumatic experience. Things would be different if I’d made a nice custom mold…

Of course, the vacuum cleaner also sucked up the odd screw, paper snippet, older swarf left in nooks and crannies, and some of this and a bit of that. Most of the junk either floats to the top or sinks to the bottom, leaving the rest of the wax in good shape. I suppose I could filter the melt, but it’s pretty thick & gooey, even at 300 °F, and I doubt my cheesecloth is up to the task.

Memo to Self: Do a better job of cleaning up before machining the wax, OK?

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  1. #1 by randomdreams on 2010-06-12 - 12:36

    I don’t know how you have your mill set up. I’ve put an old cookie sheet under the lathe for catching swarf. Back when I was a silversmith we had benches with pull-out catch drawers, one for gold and one for silver, so you’d pull out the relevant drawer under the area where you were cutting, to catch all the bits, but that’s overkill for a mill, I think.
    In any case, it’s really cool you managed to catch what you did.

    • #2 by Ed on 2010-06-12 - 19:48

      The mill is bolted to a chunk of kitchen countertop and I just aim the suck-dog hose at whatever the mill is chewing on. Low-budget and reasonably effective; I spend far less time actually milling than I do setting up & dry-running. One of these days I must set up something more formal in the way of a vacuum swarf collector.

      I was astonished that the machinable wax from those two little case halves completely filled the bag: it was basically a soft-sided brick. I think the chips were rigid enough that they locked together inside the bag, letting plenty of air through while forming a stiff mass.

      The lathe, on the other paw, has a humongous aluminum tray below the chuck which catches pretty nearly everything. I shovel that pile into a big paper bag and march it directly to the trash can every, oh, two or three years …

      • #3 by randomdreams on 2010-06-14 - 14:50

        The vacuum swarf collector I had on my previous lathe was an old (and I mean 1955) Hoover vacuum cleaner under the lathe, with some flexible plastic tubing connecting the end of the hose to where it was attached to the cross-slide just above/behind the toolpost. That managed to catch probably 80% of the swarf, and wasn’t too terribly in the way. Of course, if I was doing an uninterrupted cut of something stringy it didn’t work worth beans. But that’s why chipbreakers were invented, right?

        I saw a webpage somewhere by some guys who had milled a replica Ford Cobra out of solid aluminum: the whole frame was composed of pieces of 40mm thick sheet milled out and bolted together. They had a 40 cubic meter dumpster they filled every day for a couple months with the swarf from that. It’s unbelievable how much space that stuff takes up. Time for a good garbage compactor.

        • #4 by Ed on 2010-06-14 - 16:38

          an old (and I mean 1955) Hoover vacuum cleaner

          Probably a compadre of the Electrolux I’m using. The thing came with the house and works better than the Samsung we bought a decade ago. Quiet, powerful, exactly what you want in a suck dog.

          And when you go to buy new bags, there’s only one choice: the same bag fits every Electrolux ever made. A tip o’ the engineer cap to them!

  2. #5 by david on 2010-06-14 - 19:50

    When my old university’s auto racing team decided one year they were sick of welding wheel flanges to half-axles and were going to make the entire assembly by the elephant method (Start with a 600lb piece of 4130 round, remove everything that doesn’t look like a 4lb half-axle), I got to discover just how much space 596 pounds of 4130 swarf takes up. Times six. It’s pretty impressive.

    • #6 by Ed on 2010-06-14 - 20:55

      Start with a 600lb piece of 4130 round

      I suppose if you’re not footing the bill, billet makes a perfectly good starting point…

      A few days ago I mooched a slab of 3/4″ aluminum plate from my buddy Eks; we spent quite a while going through his stock drawers to find the smallest and ugliest chunk. Not that he’s a cheapskate, mind you, but we both know you always start with the least-desirable stock and never machine off more than you must.

      After all, you might need that slightly bigger / prettier chunk for something else!

      A bit of bandsawing, a few skim cuts, and it’ll be just right for the next step …