About acrylic blanks

[avbill]

My last two acrylic blanks both an acetate and a inlace acrylester blanks cracked from one end. up just 1/4 of an inch. enough to show that something went wrong. the one thing that stands out is that I tighting the mandrel nut too tight. In all probability its the nut been too tight yet i know its pretty loose with just a thumb tight.

The lathe is running at 1800-1900 rpm.
I'm use sharpen tools
I also allow the glue to dry 24 hours before turning the pen. I'm puzzled.

If there is anything I might be doing wrong let me know thanks

bill Daniels

 

[alphageek]

My answer to the above problem came from discovering 2 things - 1... How to use a sharp skew (both the sharp and the skew were keys) and 2... Up the speed.. Believe it or not, I turn acrylic at 3900 rpm now.

 

[Texatdurango]

Bill when you trim your blank ends, do you make sure the blank is dead flush with the brass? I had a blank or two crack on me and I found that when everything was mounted for turning the bushings were actually applying all of the pressure on the blanks themselves instead of spreading the load to the brass tube as well.

Might be worth looking into.

 

[rlharding]

Another thing: did you glue the ends enough?

 

[fernhills]

One other thing, you can loosen up on the nut some when it is down to it final dia. then sand or whatever,also turn at highest speeds sand at its lowest speeds,plastics get hot easy..good luck, Carl

 

[MobilMan]

Brass nut too tight????? I tighten mine until it is fairly hard to twist the blank on the mandrel. Are you starting your cut about 3/8 to 1/2 from the end of the blank & working toward the end. Never start in the center or off the end comming onto the blank. A fluted spindle gouge used like "U" will cause catches. A 3/4 gouge without the flutes turned at an angle "/" will make a sheering cut. Actually held more at [clock 2-8] position. Use thick ca glue. After sanding your tubes, wipe them off & blow out the drilled hole in the blank. Using the gouge like this works like a skew but a lot easier to control. Hope you don't have anymore blowouts.