The Kinport handles were machined from blocks of UHMW plastic. It was food grade plastic since Steve Howard designs and builds food processing equipment. It is the kind of plastic used in building industrial factory production food processing equipment. Seemed to work OK for handles and is machinable.
The Wikipedia article on UHMW polyethylene gives some links to other similar materials in the See Also section.
Molds for plastic parts are expensive. Many many thousands of dollars expensive. It is not practical to make small production runs of molded plastic parts. It’s too expensive. It would be cheaper, stronger and more practical to hand make a few parts like that from carbon fiber than to make a mold and make the part from plastic.
Just machine it. It’ll be fun and pretty relaxing machining, since it’s mostly just shaping the plastic. For the final contours, you can use a very rough file (look for vixen files, we used them on plastics and aluminum at work) to take off material.
Use a two flute endmill for everything. A “high helix” or “aluminum cutting” endmill would be good, since you want quick chip clearance.
John’s right. Molds for plastic are expensive to the point where it would be unreasonable to make your own. That is also why Kris avoids modifying his handles so much. Even making changes to the mold itself can cost thousands of dollars. Kris has an easier time adding material to the handles rather than taking it away since he can just cut some of the mold away. Removing material from the handles means making a whole new mold. At least, that’s how I understand it.
Don’t use lexan. It’s disgusting to machine, and much to brittle (will crack or chip into sharp corners). I have a bunch of scrap UHMW and Lexan stock in my basement, and I stopped machining lexan early on because it just smells disgusting and the chips are bad for the lungs.
I don’t see why you couldn’t make a plaster mold from an existing handle and pour yourself handles. You are correct in that manufacturing an industrial mold would probably be around $30,000US. However if you are willing to pour say 10 moulds to get a good one and willing to work on it a little bit then a plaster mold should be good. That is how I made diving weights. Actually I used soldering alloy 62%Sn 36%Pb 2%Ag and with that 2% silver they came out much shinier than just plain lead!
Good God Unicorn! We’re talking about injection molding plastics, not plaster casting lead! (As a side note, we did lead castings at the place I used to work. You need to make sure your plaster has absolutely ZERO water left in it when you cast, unless you like to see volcanoes of molten lead sprayed up into your face and then a final casting with a bubbly, pitted surface. Ask me how I know). You can’t just cast plastics like you do lead.
Evan, you’re overthinking this. Just go get a belt sander (not the hand held kind) or a faceplate sander and then just sand the curves. It’s easy. Wear a dust mask to protect your lungs. Or get a coarse mill file or vixen file and use a vise and a file to file the curves. It’s kinda fun to sculpt things this way, and the end result can look very good if you’re patient.
For the inside curves, you could do it with a router bit as you describe, but honestly, drill press bearings aren’t meant to take those kinds of side loads, and router bits are meant to run at speeds 2-3 times as fast as your average drill press will run. But most importantly, this sounds dangerous. Dangerous as in an excellent way to lose a finger, if not worse. If you do go this route (no pun intended) take very light cuts, and keep the quill as retracted as you can to reduce flexure.
if I were you for inside curves I’d just drill large holes to make the curves. Then file them out so only 1/4 of the hole is left, leaving you hour curve. Just remember, a drill bit is meant to drill through solid stock, not a half load. So don’t drill a hole if the drill bit is only going to hit on one side. That’s a recipe to ruin the part and the drill bit and also yourself and the machine if you’re unlucky.
If you make it in wax that you can easly sculpt you can then put it in plaster with just a small hole at the top. When the plaster sets heat it so the wax melts out then pour your plastic in the hole at the top when that sets you can just smash the plaster and remove your beautiful handle. The wax will probly work as a bit of a release agent as well. This should make a nice handle with little effort and work and shouldnt cost much.
i say use gerblefranklin idea, its simple and will give u a result. Albeit maybe not a great one. Don’t cast it, that probably won’t work.
@Borgschulze - you’ve never seen delrin crack? lol i used to have some delrin waterblocks, and although tougher than acrylic ones, they are still very crackable and quite rubbish. Metal waterblocks are the onyl way forwards.
you know mark that is actually a good idea… although it would only be good for a one off.
i have been thinking of making a cast aluminium handle by making a mold im pottery clay then ovening it, then do trial runs with lead and when the shape and method is all sorted out melt some alum and tip er in…
although i am always busy and am also poor so i cant afford a big block of clay.
but recently i have decide to make a reeder style handle that uses the same mounting holes as a kh handle so i dont fill my carbon base up with holes.