C-clamp thumb screw

Discussion in 'Sand Casting' started by Petee716, Oct 8, 2021.

  1. Petee716

    Petee716 Gold Banner Member

    I got a request from a friend to make a couple dozen thumb nuts(?) that he can fit to various c-clamps. I didn't ask him too many questions about his application yet. (He's an old tradesman and knows what he wants. He's 88 and has probably forgotten more than I'll ever know.)
    He wants them 3 inches long and with enough beef in the center to drill various sized holes for different sized clamp screws. Shaped like a "butterfly". I'm picturing something like this.
    images.jpeg

    My guess is that these are normally forged. I'll be discussing his end uses at some point with him to decide what material to use but I wanted to toss this out to the forum to get some ideas. I'll be sand casting. My material options at this point would be aluminum, everdur, or cast iron. Aluminum just seems wrong for the job. Bronze is awfully bendy, and CI might be too brittle. Old Ray is a woodworker though, so the last two options might still be reasonable.
    I might be able to get ahold of one to use as a pattern and make several duplicate patterns in hydrocal so I could cast half a dozen or so at a time.
    Any thoughts?

    Pete
     
    Tobho Mott likes this.
  2. Wingnuts!, also a slang term for people with big ears in Australia. Why not make them in brass: stronger than aluminium, will bend rather than break and highly machinable.
     
  3. Melterskelter

    Melterskelter Gold Banner Member

    I do think you could also make them in CI. With that wingnut, he would be hard pressed :cool: to break them. Dropping them onto concrete would not cause them to break. Bronze would be very nice and I would think very capable. Also, polished up, bronze would be beautiful. Aluminum made with a good robust design would also work fine for for woodworking. I am thinking just a bit beefier flanges on the I-beam cross section. He might appreciate the light weight. Sounds like a fun project and probably gonna learn a thing or two along the way from this guy.

    Denis
     
  4. DavidF

    DavidF Administrator Staff Member Banner Member

    I'd go with the everdur for the ductility..
    Plus you can braze to it...
     
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  5. Petee716

    Petee716 Gold Banner Member

    That would resolve the attachment question.
     
    DavidF likes this.
  6. Petee716

    Petee716 Gold Banner Member

    I decided to cast it in iron. 6 molds. 1 success, 5 failures. Metal just not quite hot enough I believe.
    20211205_140148.jpg 20211205_143342.jpg 20211124_221801.jpg
     
    Tobho Mott and Mark's castings like this.
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Like the flasks. You'll get'em next time Petee.

    Best,
    Kelly
     
  8. Petee716

    Petee716 Gold Banner Member

    I first tried making multiple patterns with machinable wax but that was a no-go. Too much shrinkage. Then I spotted a length of soil pipe that fit the bill nicely. I hope to get productive use out of them. The cost of the clamps added up.

    Pete
     
  9. DavidF

    DavidF Administrator Staff Member Banner Member

    Or you forgot to say the magic words.....
     
  10. Melterskelter

    Melterskelter Gold Banner Member

    Ohhh so close! Sure looks like it was just a tic cool.
    Yup, next time.

    Denis
     
  11. Petee716

    Petee716 Gold Banner Member

    Hoping to get a tip here.
    Question: How can I tell when it's hot enough?
    I had a fair amount of gooey slag which I was able to scoop out (mostly) while the crucible was in the furnace. I put in the measured amount of FeSi and could see it dissolving. I gave it a bit of a stir and fired the furnace back up for a few minutes. I skimmed one more time. I removed the crucible and set it on a plinth block for maybe a minute. I was fumbling with something. When I went to lift the crucible there was a somewhat light skin on top which I skimmed off, then poured.
    I know times-a-wastin once the crucible is out of the furnace but I dont think it was hot enough to begin with. Perhaps part of what I thought was thick gooey slag was actually slushy iron?

    Pete
     
  12. The few times I hit the right temperature there was a solid crust over the metal which was a very runny liquid and had a weird optical effect like it was yellow hot and highly reflective as well. I've also struggled to get it as hot again and the metal while molten had lumps of unmelted material in it. If it's runny like water and glowing yellow with the weird surface optical effect then it's hot enough. You can see in the photo the dark solid surface oxides and immediately below that, fresh iron looks slightly less bright just before it exits the crucible and that's the bit with a weird optical effect.



    iron pour.jpg
     
    Last edited: Dec 6, 2021
  13. Melterskelter

    Melterskelter Gold Banner Member

    I think trying to visually gage adequate heat of iron is very very difficult. For any kind of consistency, I think a reliable temperature probe is mandatory. For me, that means using a type S thermocouple in an immersion probe like those used in commercial iron foundries. Because of variations in ambient light and the fact that visual differences between 2400 and 2550 are subtle, I still can’t accurately guess temperatures. I have noticed that my metal remains shiny after skimming if my crucible is 3/4 or less full. But, a very full crucible will develop a dull film even at full temp—-no skin though. Here is a thread where I talk about the tips. I think folks have found readers that directly convert mV readings to degrees F or C. I just use a table of mV readings and know 14.1mV is my target temp.

    http://forums.thehomefoundry.org/in...re-metal-temperature-and-how.1344/#post-31233

    Secondly, you have a max of five mins from inoculation with FeSi to have the metal in the mold. Otherwise the desirable properties of FeSi are lost.

    For me, I’ve got to hit that temp within a tenth or two of a volt for good results, but most of my molds are fussier than the average mold. If your iron had been hot enough, those molds all would have filled. For a smallish crucible I would turn off the burner and skim in the furnace to reduce heat loss. Then drop in and quickly stir the FeSi. Then I’d try to be as smooth as possible to pull, transfer to a pouring shank and pour in under a minute. I’ve found it helps me to rehearse the necessary moves and make sure everything is in position prior to pouring.

    Denis
     
    Last edited: Dec 8, 2021
  14. Petee716

    Petee716 Gold Banner Member

    Thanks for the tips guys. I'll give it a go again this weekend weather permitting.
    I wonder if my molds being 35F contributed to the issue.
    Pete
     
    Last edited: Dec 7, 2021
  15. Melterskelter

    Melterskelter Gold Banner Member

    I think it contributed, weakly. The metal should flow into those molds in less than 5 seconds. Not much time or very good contact for cooling.

    Denis
     
  16. DavidF

    DavidF Administrator Staff Member Banner Member

    Pete, I don't know if you've ever noticed, but I do my skimming and inoculations with the furnace running through the vent.
    This keeps the melt from being exposed to the atmosphere... very beneficial for me ;)
     
  17. Petee716

    Petee716 Gold Banner Member

    I find skimming iron to be an awkward affair. Doing it through a 4" hole while running sounds daunting, but I'm willing to try. Do you have video?
     
  18. DavidF

    DavidF Administrator Staff Member Banner Member

    Pretty old video... at the 2:15 mark you'll see me pick up a bent metal rod. In the end of it there is a chunk of magnesium ;) but I chickened out :rolleyes:
     
  19. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    What size crucible and lbs of melt Petee? Small melts lose heat very quickly compared to large ones.

    Best,
    Kelly
     
  20. Petee716

    Petee716 Gold Banner Member

    It's an A10 salamander with about 10lbs of metal. So, yeah, too much lag time.
     

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