Tips for Machining PVC Plastic

[Jarh73]

Just after some wisdom from the collective.

I'm machining up some plastic bushings out of PVC.

I sharpened up a cobalt (Looks like HSS but has cobalt written on it) piece of tool steel.
It cuts really well and leave an excellent finish but its makes lots of strings, for want of a better word.
It doesn't make actual chips.
The stringy stuff just bunches up and makes a big birds nest.

I don't need to remove a lot of material so that's maybe why it won't chip.

Any hints or tips or pictures of how to sharpen a tool for machining plastics?

Cheers

Justin

[DaveTTC]

Plastic, acrylic etc does just what you are saying. If it came off in chips likely there would be a problem like blunt chisel etc.


Any woodturning chisel should turn PVC as I imagine steel machine bits would too

[Jarh73]

Yeah I thought as much!!!

Its cutting beautifully actually just messy stringy stuff everywhere and it bunches up.
Mind you it doesn't affect the surface finish.

Cheers

Justin

[j.ashburn]

Try a piece of hss with a groove ground across the rake face might help othrwise you going to make lots and lots of string.groove will distort the chip flow.might have to play with it.sssh........t stuff to do like nolothane.

[Ueee]

I have only ever had it come off in strings. Nice sharp tool, highest rpm possible and it will cut very cleanly. I machined up some gear blanks a while back, I had ribbons flying a couple of meters.
Cheers,
Ew

[Gerbilsquasher]

Here's a good tip... don't get it too hot or you will die.

The gasses released by heating PVC include cyanide which has well-documented evidence of reduced longevity.

Machining PVC with coolant should be perfectly safe. Hell, I have even cut PVC tube with my cutoff saw.... not dead yet. Repeated use in an enclosed space might not be healthy......

I am not trying to spoil your fun. Just be careful :wink:

[Grahame Collins]

HSS is the way to go, but you won't get a chip from it.

If you do get plastic to chip, let us know as no one I am aware of has done it, mentioned it, written about it or posted it on the web.:D

The HSS should be well sharpened with the cutting edge honed to a extremely sharp edge by a finishing stone and turned at high rpm.

I have turned about thirty odd jobs of the black poly solid stuff over the years and never got it to chip. Good finishes were attained through sharp edges and high RPM.



Grahame

[jack620]

Machining PVC with coolant should be perfectly safe.

I think compressed air is used to cool tools when cutting plastics. I've been meaning to setup a flexible air nozzle on my lathe for turning Delrin.

[Oldneweng]

I think compressed air is used to cool tools when cutting plastics. I've been meaning to setup a flexible air nozzle on my lathe for turning Delrin.

Good tip. Have to remember that one. I have to cut 2 panels of perspex to replace broken windows on my new canopy soon. It came from the wreckers and was cheap. May help with the cutting.

Dean

[rodweb]

For HDPE, the best finish I got was when the power cross feed was set up for threading M12x1.75. The finish was near mirror like! Things happened scary fast with that setting at maximum RPM so I face my parts by hand now. I move the tool a lot faster than ally, but not as fast as I can wind the handle.

[Jarh73]

Well its nice to know I'm on the right track!

Thanks for all the hints, tips and safety advice.

Its machining beautifully and no signs of extra heat.

Cheers

Justin