Bad Acrylic blanks or bad turning opinions please.

[Chuck B]

Well I bought 8 Acrylic blanks from a well known company I made 3 came out great(dark color blanks). I made 3 more (light color blanks)& you can see a ghost image of the gold tube. The last 2 are a light color & I see what looks like a line that goes from one end to the other about 3/16". As I was using Maguires wax on the last one the line split & cracked to the tube.Did I turn it to far down? it came out exactly to the bushings. I started sanding with 400 & went to wet/dry car sandpaper to 1200 grit. Did I do something wrong or did I receive a bad batch of Acrylic blanks.
I do know I really don't like to turn Acrylic maybe that's because of what happened. I took VERY LIGHT CUTS. I used a Sorby Spindlemaster & for final smoothness a Sorby 3/4" skew held horizontal & perpendicular to the ways. just kissed the blank.

Opinons please.

Thanks

Chuck

 

[its_virgil]

Chuck,
The blanks are not bad. What you are seeing is the brass tube showing through the acrylic. It happens when the colors of the blank are light and somewhat translucent. There is a cure. Check out this thread:

http://www.penturners.org/forum/topic.asp?TOPIC_ID=17951

You may want to do some searching for ohter info. We have a great search function here.
Do a good turn daily!
Don

Originally posted by recon
<br />Well I bought 8 Acrylic blanks from a well known company I made 3 came out great(dark color blanks). I made 3 more (light color blanks)& you can see a ghost image of the gold tube. The last 2 are a light color & I see what looks like a line that goes from one end to the other about 3/16". As I was using Maguires wax on the last one the line split & cracked to the tube.Did I turn it to far down? it came out exactly to the bushings. I started sanding with 400 & went to wet/dry car sandpaper to 1200 grit. Did I do something wrong or did I receive a bad batch of Acrylic blanks.
I do know I really don't like to turn Acrylic maybe that's because of what happened. I took VERY LIGHT CUTS. I used a Sorby Spindlemaster & for final smoothness a Sorby 3/4" skew held horizontal & perpendicular to the ways. just kissed the blank.

Opinons please.

Thanks

Chuck

http://www.penturners.org/forum/topic.asp?TOPIC_ID=17951

 

[ctEaglesc]

Just a sawg but the cracking came from the "shock" while you wwere roughing the blank.It helps to ease the corners.
(of course you could resort to wood[])

 

[Chuck B]

I tried both ways going from the ceter out then just kissing the corners going in. I took very light cuts It took me 4 times longer to turn these then wood I went slow so I wouldn't screw up.

Eagle the cracks are from my initial roughing that transmitted to the center of the blank?

Virgl,
Thanks for the link I forgot about that[:I]

 

[JimGo]

Try cutting the corners off on the bandsaw, or hitting them on a belt/disc sander.

 

[Chuck B]

Jim,
No bandsaw or belt sander yet after X mas.

 

[mick]

Chuck,
I use a very sharp round nose scraper to round my acrylic blanks. When I first started turning "plastics" I used a gouge and would quite often shatter or crack the blanks because of what I considered to be a too aggressive cut. By using a round nose scraper you have less surface contact with the blank and take off smaller bites ....you can actually watch the shavings lengthen as the corners are cut off. Once rounded or you can actually take it down pretty close to shape with the scraper, I switch to a 1/2 oval skew, also very scary sharp, which has been sharpened to a slightly convex edge so I don't "catch " the corners of the skew as easily. Usually when I'm finished I can start with 400 grit sand paper. Different "plastic" turn differently. Trying several manufacturers is the only way to get used to everything that's out there. As for painting the tubes as suggested above I keep ......or Connie does, a good supply of craft paints, so I mix a color close to the blank and paint the inside of the blank. This way by painting the inside of the blank vs. the tubes, the glue doesn't show through the lighter material as it's "under"the paint. This is what works for me, the best thing is to experiment and try different things. Especially if what you're doing isn't working.

 

[Chuck B]

Mick,
With the Sorby set I bough it came with a 3/4" oval skew for he life of me I can't sharpen the dam thing right. So I went & got the 3/4" regular skew. I still have to get the wolverine skew jig. Thanks for the idea on painting the blanks.

Chuck