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| awemawson:
Steve, tapping coarse acme threads, I've always bored and threaded them undersized in the lathe then used the tap as a finishing pass. |
| PekkaNF:
Once I was thinking of buying a tap roughly same size trapezoidal thread 12 mm and 2 mm lead....One Brittish tap maker I called said that that they would need to charge about 140€ of it, it needs to be long, cut gradually and all in all it is hard to make one that will work manually and will not break. I have been reading of people drilling oversize hole, using normal V-thread tap (same lead) to remove some metal firs. I believe it's not too easy. Also that size internal threading will not be easy. When you substract thread part out of the diameter, there is not much left for threading bar core diameter.....Would probably need to be as short as possible and you many need to to make two bars to optimize thickness and cutting tooth lengt - bit like first cut / second cut tap. Helix angle and all. Did not want to go there So, I'm designing that part a little fatter to make room for ready made nut. Left handed nut and trapezoidal bar are not cheap, but cheaper than the alternative. Pekka |
| awemawson:
Have you considered a quashed Acetal nut? Never done it but some swear by them - turn / bore your plastic blank with a core sized hole, place in suitable outer clamp over the acme male thread and warm and tighten. The plastic flows around the thread. You can then turn the o/d to suit. I believe a dusting of graphite powder is used on the male http://bbs.homeshopmachinist.net/archive/index.php/t-43645.html |
| Pete W.:
Hi there, Steve, This project is looking very impressive so far. Regarding your problem with taps, I've just clicked my way through about twenty pages of the Model Engineer forum until I found this: http://www.model-engineer.co.uk/forums/postings.asp?th=103007&p=28 I knew it was there somewhere! I hope it helps. |
| Will_D:
What about a multi-stage casting process to end up with bronze nuts? |
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