Yes, nozzles for the motors. I had not considered it being abrasive, isn't it used as dry lubricant? I have some people over on that side I can ask about it, I just wondered if there might be something useful to contribute here. I know some of them grind down spade bits to make form tools for the cones.
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Models for grinding HSS Lathe Tools
- Thread starter mikey
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Not having machined it I'm next to useless but just on a guess, I would personally try a tool that cuts really easily to reduce internal stress on the graphite matrix. My main concern would be to reduce rubbing that would induce heat so I would increase the relief angles. I don't think it is a particularly tough material so I would go conservative on the rake angles. I have no idea how it finishes so maybe a 1/32" nose radius?
Okay, so, I would try 15-18 degrees of side and end relief, 12-15 degrees of side rake, 10-12 degrees back rake and 1/32" nose radius. I would try it and adjust the tool angles to optimize the cut. The only way to tell is to grind a tool and give it a go.
I watched a video on turning graphite and it sends up a cloud of particles. If I was to turn that stuff, I would cover everything in the shop, cover up everything on the lathe that I could, stuff a rag or paper towel moistened with oil inside my spindle bore and put up a BIG vacuum port - maybe two vacuum ports - and then clean the lathe and the room afterwards. I would also use a respirator on myself.
Just curious by why would you use graphite instead of mild steel? Could you not use 12L14?
Okay, so, I would try 15-18 degrees of side and end relief, 12-15 degrees of side rake, 10-12 degrees back rake and 1/32" nose radius. I would try it and adjust the tool angles to optimize the cut. The only way to tell is to grind a tool and give it a go.
I watched a video on turning graphite and it sends up a cloud of particles. If I was to turn that stuff, I would cover everything in the shop, cover up everything on the lathe that I could, stuff a rag or paper towel moistened with oil inside my spindle bore and put up a BIG vacuum port - maybe two vacuum ports - and then clean the lathe and the room afterwards. I would also use a respirator on myself.
Just curious by why would you use graphite instead of mild steel? Could you not use 12L14?
Thanks for the tips Mike! I know I'm a bit off in the woods on this one. Vacuum, respirator, and others will be employed. I'm still deciding on how I want to go about it before I try cutting any. My hope, and reports from others indicate, that dust can mostly be controlled with shopvacs. I imagine speeds and feeds have to be low for that to work.
The materials are limited by the insurance carriers the national groups use. Motors and the rockets themselves have to be made from frangible material. Some steel and such can be used, but it has to be a small part of the overall mass and motor components cannot be steel. So it tends to be limited to things like fasteners to anchor recovery systems. About the only metal allowed is aluminum. If I were able to fly without the groups and deal with all the legal stuff myself, I could use steel. There are some people doing that, just not in Utah. Nozzles in aluminum don't work well due to the heat. Aluminum cases have thermal insulation liners that protect the aluminum from the worst of it. Phenolic is another choice, but it seems hard to get in large sizes. It also erodes during the burn, changing the motor performance in flight. That also means the nozzles can only be used a small number of times before they erode too much. Graphite tends to hold up for dozens of flights.
The materials are limited by the insurance carriers the national groups use. Motors and the rockets themselves have to be made from frangible material. Some steel and such can be used, but it has to be a small part of the overall mass and motor components cannot be steel. So it tends to be limited to things like fasteners to anchor recovery systems. About the only metal allowed is aluminum. If I were able to fly without the groups and deal with all the legal stuff myself, I could use steel. There are some people doing that, just not in Utah. Nozzles in aluminum don't work well due to the heat. Aluminum cases have thermal insulation liners that protect the aluminum from the worst of it. Phenolic is another choice, but it seems hard to get in large sizes. It also erodes during the burn, changing the motor performance in flight. That also means the nozzles can only be used a small number of times before they erode too much. Graphite tends to hold up for dozens of flights.
Most of what I'm reading online suggests carbide for tool life reasons. I only have one response from the rocket guys so far, and they also suggested carbide with a rounded end for the o-ring grooves. I suspect that's about the inside corner of groove. I have to look at the carbide parting tool and see what it looks like. I could grind an HSS blade that way easily though.
I might try some HSS just to see what the tools do on it. I have to rough cut it down to diameter anyway, might as well learn something.
I might try some HSS just to see what the tools do on it. I have to rough cut it down to diameter anyway, might as well learn something.
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I'm interested to hear what works on graphite as well. I need to turn a couple of graphite pistons for a Jan Ridder design flame eater. I did find this info:
http://www.substech.com/dokuwiki/doku.php?id=machining_graphite_and_carbon
http://www.substech.com/dokuwiki/doku.php?id=machining_graphite_and_carbon
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Brento
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Mikey i love the instructions. Great work. Im going to make aluminum and brass cutters from this. Im thinking of making both tools for each material.
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I've been sort of bouncing this around inside my head for awhile and I'm wondering how a square tool would cut this material. The square tool has 15 degree angles all around. That gives us enough relief on the side and end for almost any material, and it has decent amounts of side and back rake to reduce cutting forces so I hope this enough to prevent chipping at the cutting interface. The only way to know is to cut it.
@ttabbal, why not try the square tool on some spare graphite and see how it works? It would allow you to see how the tool performs and hopefully spot any deficiencies. Then we can modify the grind to resolve them.
@ttabbal, why not try the square tool on some spare graphite and see how it works? It would allow you to see how the tool performs and hopefully spot any deficiencies. Then we can modify the grind to resolve them.