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putting a thread in a cast


soctal

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hello, i am getting into casting because there are specific unique parts i must make, some of these parts need to have threads in them so i can screw them to plastic resin parts. if anyone knows how to do that, or if it can be done, please let me know? i dont know if that is possible in the casting stages or will have to have a machinist put it in or can i do that myself without a metal lathe? i do have a drill press.. thanks.

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Giving the size that you want to thread would be helpful. If its under 3/4" you can hand thread with a die. Put your piece in a vice and turn the die set with the appropriate wrench. A twisting wrench with 2 handles will work too. The main thing is to start it straight. As a millwright I tap and die rod and holes all the time. Sometimes up to 1 1/4".

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All castings are rough after pouring - there are investment materials that let you hold an incredible amount of detail but there's shrinkage rates to calculate to get your thread area anywhere close to accurate. Even if you do, you would still need to run a tap through any cast threads to make them usable. You're better off making a "place holder" (indentation in the master-form as a start point for the drilling) then drilling and tapping. That being said, I'm speaking from a large scale casting perspective so there may be someone here who does jewelry level work that has a technique for you.

You shouldn't need a machinist to drill and tap them unless the tolerances are critical - if you're willing to cast your own parts, then make the investment into a set of taps and dies - it'll save you money and time.

Good luck - let us know how it turns out!

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Need some details to help you better.

Internal, or external threads.

Size of thread IE; 1/4-20, 1/2-13, 4mmx.7mm etc.

Length of threaded section. BIG difference in doing one from 1" long, and say 4" long.

Type of thread. Vee, Acme, square, buttress,single, or multiple lead, etc.

Type of material being cast. Brass, steel, aluminum, resin.......

What is said item being used for? Strength needed.

How many do you need to do?

Where are you located?

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