?? About Nylon/Delrin (milling?)

[kartracer55]

I need to make a chain guide/tensioner for my minibike, and I was thinking about using an idler sprocket, but decided to use Delrin instead, so my dad got me a piece from work. Anyway, It has a slot cut into it, but I need to widen it just a bit, and I have the right size endmills. A few things here... What kind of feed rate and speed should I "machine" this stuff with, and would a 2 flute or 4 flute end mill be better. I have never milled anything this soft, so what should I keep in mind when doing so? Is the softness of the material going to present a hazard? I plan on doing it on a regular old manual Bridgeport mill.

Thanks

Jim

 

[Fast Orange]

Mill it the same as you would aluminum-no coolant/lubricant needed.Any sharp endmill is OK.
George

 

[kartracer55]

So about 800 then? 4 flute because its a slot, correct?

Jim

 

[Fast Orange]

Because of the softness of the mat'l,it's very machineable and forgiving-Make a couple practice passes-you'll see what I mean.
Off the top of my head,I'd say 800 RPM is about right for 1/4"-3/8" 4 flute-about .060 depth of cut,feed to be determined by desired finish.Even a 2 flute will work-just feed slower for better finish.

George

 

[vettescout]

If you go too fast you'll heat it up, thermal expansion coefficient of plastics generally much higher than metals, water is a good coolant, delrin has a machinability rating of 1, same as nylon 101 (easiest) Another thought, it's easy to machine and I think the chain will act like a dull endmill and just worry its way into the delrin, I'd look for a more suitable material

 

[kartracer55]

If you go too fast you'll heat it up, thermal expansion coefficient of plastics generally much higher than metals, water is a good coolant, delrin has a machinability rating of 1, same as nylon 101 (easiest) Another thought, it's easy to machine and I think the chain will act like a dull endmill and just worry its way into the delrin, I'd look for a more suitable material

Yeah, the chain does eat its way into it, but I dont really know what else to use. This is actually a leftover piece of a chain guide that my dad got me from one of his machines. Im just modifying it little bit. I originally wanted to use and idler sprocket, but they are about $20, and they would make th entire setup alot more complicated, because I would need a shaft and Id have to weld on a different bracket.

Jim

 

[vettescout]

I've got a Quadrant Plastics engineering handbook laying around someplace and I'll check to see what they recommend, won't be untill tomorrow though... Paul

 

[kartracer55]

Doesnt matter, Im not starting this project until next week, Im in the planning stages of making the tensioner/guide.

Thanks

Jim

 

[avsfan733]

might wanna consider ultra high melecular weight polyethylene its the plastic they make cutting boards out of tough stuff... make sure you keep it cool wether by coolant or by a really sharp tool. same goes for any plastic its more of a concern of it melting from my experiences although not to much a problem with delrin it machines really nice we use it a lot on the formula team i work on

 

[gerry]

I bet derlin will be fine for wear. The edges of the plates on the chain will cut channels in the derlin until the rollers bottom out. At this point wear will decrease because the rollers will tend to roll over the guide rather than cutting it

 

[Cebby]

What about getting a skateboard wheel and machining it. Isn't that what those tensioners are usually made of?

 

[MXtras]

Most chain guides are made from Urethane but I am thinking Nylon would work - just keep an eye on it.

Scott

 

[Luckydevil]

Hey Jim, check this out... http://www.brpit.com/pages/products/chain_guides.html

 

[number3]

I am not sure how well it works for chain guides but Delrin makes for great shift knobs. Delrin is not cheap either. Ebay it once.

 

[kartracer55]

Thanks for all the help guys. I wont get a chance to "machine" the stuff im school until probably around january The machine was moved from the former metals room to the autoshop(over the summer) and to date my autoshop teacher has submited 4 work/service forms to get 3 phase run over to where the machine is. Once again, Horribly mis managed school system, thier priorities lie more in getting recognized as a "National school of character" than anything else. Luckily, I spoke with my engine builder, and he said hed be more than happy to let me machine it in his shop when we go to pick up our one motor, about mid december.

Luke, those chain guides are really nice, make of polyethylene it says. Thats kind of what im looking to do but it needs to be able to add light tension to the chain as well.

And yeah, I looked at the price of delrin today and its REALLY expensive. This was a piece of "scrap" though. My dad always brings me home good stuff, 1/4 aluminum plate, steel plate, angle iron, its great

Thanks for all the help guys!

Jim