pyrokid Posted March 15, 2017 Share Posted March 15, 2017 Hi everyone! I have the chance to use a machine shop to make some pyro tools. My first goal is to make come crossette pumps. However, I'm having trouble zeroing in on the correct dimensions for the pump, so I hope the community can offer me some advice. How well does a single design scale as comet diameter changes? Should the cruciform shape taper toward the timing pin? Does this help remove the pump from the star? How is the cruciform polished after machining? What is the plastic of choice for creating such a tool? Most importantly: how can I determine the right shape for the pump head? I've looked at lots of different designs, and every one is different! If I find a successful design on the internet, should attempts to copy it yield a functional tool? Are there any drawings available that I have missed? Thank you for any help! 1 Link to comment Share on other sites More sharing options...
lloyd Posted March 15, 2017 Share Posted March 15, 2017 Kid,It needn't be a cruciform shape. A square former works just as reliably to make crossettes break into four pieces. The cavity should be _about_ 33% (in width across the flats) of the o.d. of the comet, for a 3/4" comet. It doesn't change much, up to about 1-1/2" comet o.d. The pin length should be about the same as the comet o.d. The pin should be tapered about 1-1/2 degrees. I also prefer to put a small "shot tit" on the end. I like Delrin for my crossette formers. I don't require to polish mine. The machined surface is smooth-enough, and gets better with a little wear. No... no drawings. They're proprietary. Lloyd 1 Link to comment Share on other sites More sharing options...
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