I started a new turning using wood and acrylics. I have turned quite a few pieces with acrylics and come to the conclusion that they have different hardnesses and it seems you need slow rpm down a bit for some. The type of cutting tool also makes a difference, or it seems to me to be so. A HSS cutter and a carbide cutter each work better at slower speed than normal with the harder stuff. I think the key to successful turning is to take lighter cuts and slow speeds down.

 

What is your technique  with acrylics? Any advice is appreciated.

 Ron, I did a little reading on you question and came across this chart. Could it be that some of the pieces you are turning are polycarbonate and not acrylic. Just a thought.

 

https://www.acmeplastics.com/acrylic-vs-polycarbonate

Seems everything has a different cut rate even wood.  These charts that say use this RPM for that diameter never take into consideration what's being turned.  I just learn what I turn.  Play with it until I find the sweet spot.  I can send you a piece of unknown black plastic that cuts fine until the tool gets warm and then it quits taking a cut.    

Ron, I don't turn acrylics but I know  Easy Wood Tools has developed a new negative rake insert designed just for that application. Haven't tried one on acrylics but I have used one on hard wood end grain and it gave a very nice finish on that.

 

Steve

Thanks, "learn while you turn" (HandyDan) is what I going to do more of. However, my assumption that all plastic type material was acrylics was totally wrong. (Ducksoup) Thanks for the the advice and info. I am going to approach turning this material with a a lot more caution. I hate it when I am nearly finished and have a chip come out. I think that when that happened, I was using the wrong speed and perhaps the wrong cutter for what I was doing. 

 I must also say that I'm not fond of turning plastic/Carbonates of any kind. The mess made by the tailings gets everywhere and binds up most moving things. After each turning is complete, I must remove and clean my chuck (and most other things)

+1 on what @Steve Krumanaker said about the new negative rake cutters from Easy Wood Tools. I have used them on both wood and acrylics (Alumilite castings). They cut much smoother and virtually no chipout. Once rounded, I turn the speed up fairly fast. My preference for smaller turnings is the Ci5 cutter. It is very easy to control and removes only a small amount of material at a time.

 

You are correct about the mess, those stringy shavings go everywhere!

2 hours ago, lew said:

You are correct about the mess, those stringy shavings go everywhere!

 

And if you try to suck them through the dust collector they make their way to the filter because they are so stringy and light.

 I had the piece 99% done. I needed to tap a place to drill a tiny hole. That stuff is SO brittle, that it split into 5 pieces with just a tiny tap. It was time to take a break and walk away, and I did

15 minutes ago, Ron Altier said:

 I had the piece 99% done. I needed to tap a place to drill a tiny hole. That stuff is SO brittle, that it split into 5 pieces with just a tiny tap. It was time to take a break and walk away, and I did

Without seeing what you were doing this is just a shot in the dark. When I'm doing small ornament finials I drill and tap them long before they are turned to a small diameter. If I don't they will often split because there just isn't enough material left to keep that from happening. When they are done installing the screw eye is no big deal.

 

Steve

Thanks Steve, I normally have the drilling done also. However this stuff is so brittle, the original piece with the drilled hole...............broke a chip off and I had to turn some more off. I was in the last procedure, redrill the hole and finish. I was making a tiny mark to start the drill when it happened. I will not use this type of material again on an ornament or anything small. I'm going to finish it as it is, chip and all. I'll post a picture if it turns out 

It may not apply in this situation but when I drill holes in plexiglass sheets (acrylic?) I make sure to hold the piece tight to a scrap backer.  And I prefer to use a brad point bit.

 

@Ron Altier

Perhaps I don't understand your use of the term "tap" here, but I would use a piece of painters or masking tap to wrap the piece, mark the hole and with a brad point bit no "tap" in the metal working sense would be needed...

Cal, this darn stuff is like glass and twice as brittle. After it broke off as I was finishing it, I turned it to a smaller diameter and needed to redrill a tiny hole in the end. At this point I had no alternative but to use a very small drill and bit. I've done this many time before, but not on an extremely hard/brittle piece of plastic. I used an ice pick and attempted to make a small surface hole/dent to start the tiny drill. One light tap and it broke into 5 pieces. I did them drill it a hole successfully but am at a standstill until I figure out how to fix the situation.

Don't give up on turning with the stuff.  I have tons of Corian sample squares and wasted a few just learning to spin them down without chipping them to death or breaking.  I found it is best to not turn them down to small diameters.  Common use has been white Corian on the ends of fan pulls.  Taught my kids white is light to help them remember the white ended ones were to turn on the fan light.

 

I know others recommended some great ideas for tooling and that will help.  All the pens in the box I made with a HSS gouge and skew tool.  They do dull quickly messing with this stuff so the carbide tips should be a big help in this regard.

@Ron Altier, even the sharpest of an ice pick is still a wedge when tapped.  As an experiment I wonder if you used your drill bit on high speed and go slow enough to "melt" through.  But then you might end up with a hole needing clean up, ending up melting it all back together again...

Check out this video regarding some specialty drill bits.  He mentions a 3/16" is in the set:

https://video.search.yahoo.com/search/video?fr=yfp-t-s&p=how+to+drill+a+hole+in+acrylic#id=3&vid=f20aa5456bdcb544b6bc27d30237b156&action=click