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| PekkaNF:
--- Quote from: vtsteam on May 07, 2015, 05:06:23 PM ---Not sure what you mean Pekka. No matter what shape the flutes, the screw can only make its own shape in another solid. A different shape flute relief will affect the ease of cut, only. Commercial taps have radiussed relief cuts mainly to reduce notch sensitivity I believe, so the tap will break less easily. --- End quote --- You are right. I was too tired when I was thinkking of this...like helix angle + side clearances and projections. Like gear cutter. Any change of a separate how-to-thread with a little text and few picures on how you did that tap. I am specially interested on case hardening. There used to be many chemicals awailable here, but most seems to be either forbiten on unobntanium for hobbyist. Pekka |
| Will_D:
--- Quote from: vtsteam on May 07, 2015, 07:44:17 AM ---Will, In this case I need to tap the casting. --- End quote --- My idea was more along the lines of: Take a silicon rubber mould off of the thread. Fill this with investment, remove silicon. Use the male invetsment as a core for the cast bronze. Or similar using a lost wax master of the leadscrew. Only trouble may be shrinkage! |
| vtsteam:
Thanks Abraham, Pekka, Will! :beer: :beer: :beer: Pekka, I used Kasenit to case harden the tap. I have a can of it bought a dozen years ago. I don't know if it's still available. Lookups on the net aren't showing it other than providing references to alternative products, or case hardening discussions. Will, I meant I had to tap a hole in the carriage casting itself, rather than produce a separate leadscrew nut for the carriage. That's why I needed a tap. Your method seems to imply making a new small part (like a leaadscrew nut), and so it's definitely possible to core a thread in that kind of thing. The Gingery lathe I built has such a casting -- the split nut. |
| S. Heslop:
Last week I was looking up the prices of acme/ trapezoidal taps and got a fright. I then proceeded to try find information on making taps and found nothing but garbage. So this stuff is very much appreciated! |
| vtsteam:
Simon, Pekka, there's a lot of reference online to homemade case hardening compounds. I haven't tried any of them because I already had Kasenit, though I'm very interested in simple materials. It's hard to sift through all the claims and counterclaims, and I don't want to experiment with the ferro or ferri cyanides based on various sometimes opposing opinions. And those recipes calling for many hours packed in bone, hoof, horn or leather (and there is disagreement about which is best) sealed in stainless boxes at yellow heat isn't practical for me. It would be nice to have a tested way of case hardening even light depth that was both safe and quick, and involved available materials. I think Andrew, you once mentioned something along those lines -- can't remember..... The other way to make a tap is to start with hardenable material like drill rod, then turn the thread, mill the flutes, and harden and temper. |
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