turning plastics,nylon

[thomas harris]

made a part last night and it turned out fairly well for an old "hammer-mechanic" like me. Is there a way to get the shavings to stay off the turning piece, or is a vacuum system really required with these materials. Had to shut down a few times to clear the mess. Kinda annoying. Nylon is really stringy stuff! Hope I'm not wearing out my welcome on this board, but I just recently bought the lathe and have lots of questions about techniques. My four jaw chuck came yesterday and that is the ticket four the plastic stuff. Kinda wild chunking off the corners on the square stuff, but in town there is a supplier who sells the "'chunks" by the pound and real cheap. Lots of various plastic too.

[Jake davis]

When I machine Delrin and Nylon I am able to snag the first couple of coils and pull as the lathe feeds. Most of the time it will come off in one continuous string. I have expirienced the wrapping you speak of and it is rather annoying.

-Jake

[walt37]

If at all passable cut the plastic with a utility knife ,then as you turn off material it will break into short strings as your tool bit crosses the knife cut.
You can also mill a slot if you have access to a mill.
Watch out those tong strings of plastic can't be yanked out by hand with the lathe running,[don't ask how i know]

[Steve_in_Mich]

in town there is a supplier who sells the "'chunks" by the pound and real cheap. Lots of various plastic too.

What town would that be, if you don't mind sharing. I'm in Midland.

I turn a fair amount of ABS and it reminds me of earlier days fishing with an open reel and the occasional "birds nest" tangle. I have turned some rubber pull rolls with similar results.

[JimGlass]

Plastic is interesting stuff to machine. Each type of plastic has their own characteristics when machined. Turning is usually the most challenging because the chips come off in continueous strings, curls or ribbons. I always liked seeing ribbons come off becuse they could often be directed into the trash can. Achieving the desired chip is a combination of tool condition and feed rate. If the tool is sharp and has a fairly sharp tool nose radius then experiment with the feed rate. Higher feed rates seem to work better overall compared to slower feeds.

Never allow plastic to become warm while machining. My home brew plastic coolant is dish soap and water. The soap lubricates and the water cools. Coolant is important when tapping plastic. It is possible to break taps in plasics (Lexan) because of the heat generated. I have seen plastic melt while tapping then solidify before the tap retracts.

Below is a picture most should find interesting. I found the 35mm snap shot recently and took a digital pic of it just now. I'm machining a feed screw made of delrin plastic. The screw portion is a radius much like a ballscrew. A boring head is used to make the radius on the feed screw. There is also a bushing coated with blue layout die that indicates when the final depth of the radius has been reached. The drive shaft at the left is screwed to the delrin shaft to drive rotation. The same shaft is used to rotate the feedscrew in the final automated device.

I'm using #25 roller chain and sprockets with a 5:1 ratio to achieve the 1" pitch of the screw. I made many, many feedscrews with this set-up. It is probably my most creative set-up ever.

During set-up a dial indicator can be used to check for taper in the spiral. The final feedscrew is nearly free of taper and runout.

Jim

[kencaz]

Is there a way to get the shavings to stay off the turning piece, or is a vacuum system really required with these materials. Had to shut down a few times to clear the mess. Kinda annoying. Nylon is really stringy stuff!

We had to bore some large abs sprinkler parts once and had a similar problem with the shavings. We ended up turning the boring bar over and cutting from the backside. It worked well because the shavings went straight downward.

You may try reversing direction, and either turning the cutter over or cutting from the other side.

KC

[tattoomike68]

Plastic can generate a huge volume of chips. I have turned more than my fair share.

I saw a 5 spindle screw machine set up to make shoulder bushing and there was air hoses mounted all over the place to eject the chips out of the machine and a dumpster on each side of the machine to catch them all. The dumpsters would fill up very fast with the high speed machines.

That was the job given to the shop screw up, it was hell. whoever was not doing a good job got stuck doing that nightmare.

[Harold_V]

It is probably my most creative set-up ever.

Beautiful setup, Jim.

I can see how I could emulate the same concept to create a form for winding a coil for an induction furnace. I just may have to give that a go in the future.

Harold

[thomas harris]

in town there is a supplier who sells the "'chunks" by the pound and real cheap. Lots of various plastic too.

What town would that be, if you don't mind sharing. I'm in Midland.

I turn a fair amount of ABS and it reminds me of earlier days fishing with an open reel and the occasional "birds nest" tangle. I have turned some rubber pull rolls with similar results.

Alro metal Plus is the Company. They have a branch in GR and Kalamazoo that I know of, perhaps others elsewhere.

[Charles T. McCullough]

I turned a bunch of plexiglass 'laser rifle' barrels ("Lost in Space" replicas) for a friend and had plastic ALL OVER DA PLACE... up to my knees at one point! When I vacuumed it all up I figured I'd have to empty the canister at least twice or more, but the stringy stuff shattered in the vacuum hose and there was only about an inch or two of gritty dust in the shop-vac when I was done.

[Jose Rivera]

Never use alcohol with acrylic plastics (Plexiglas).
Alcohol will crackle the material to pieces specially if it has been machined or drilled.

Try on a piece of scrap by drilling a hole in it and then use a little of alcohol and see what happens.

Even some called plastic cleaners will cause cracking on machined Plexiglas.

[Charles T. McCullough]

Never use alcohol with acrylic plastics (Plexiglas).
Alcohol will crackle the material to pieces specially if it has been machined or drilled.

Try on a piece of scrap by drilling a hole in it and then use a little of alcohol and see what happens.

Even some called plastic cleaners will cause cracking on machined Plexiglas.

I gotta go try that!