# Acrylic Acetate Problems



## Herb G. (Nov 24, 2017)

Sorry I don't have any pics, but I will try to describe what happened best I can.
I turned only my 2nd AA blank today. I took it down as close to the bushings
as I could. Then, I sanded it the rest of the way.
When I stopped the lathe, I see cracks & crevices in the blank in the direction
of turning. Sort of like deep scratches, but actual cracks.

They did not fill in with CA, and the whole blank is pretty much translucent now.
In other words, ruined.
Any ideas on what happened? 
Did the AA get too hot from sanding & craze?

Any help is greatly appreciated.


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## duncsuss (Nov 24, 2017)

Acrylics do not like heat (and some don't like it much more than others). If you could feel the sand paper getting hot, that was probably where things went wrong.

I usually wet-sand acrylics, and turn the speed down to 1000 rpm or slower.


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## Schroedc (Nov 24, 2017)

Acrylic Acetate is usually fairly forgiving. I turn a LOT of it, Higher speed than wood, scary sharp tools (I use EWT carbide style myself but you can use a skew or gouge too) Take really light cuts then wet sand at a slow speed. Depending on your tube size, your wall thickness may be thin enough that that particular acrylic is pretty see through and some of what you;re seeing may be from drilling it as well. You can address some of that by painting the inside of the blank after drilling before you glue in your tube. I generally start at about 320 and wet sand up to 2000 or more and then polish with 3M automotive rubbing compound. No other finish.

Reactions: Agree 1


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## rocky1 (Nov 24, 2017)

I'd be more inclined to believe the scratches you encountered were derived from drilling the blank for the tube than from sanding. You should feel heat well before anything sticking to your paper and scratching the blank that bad. Wet sand, with lots of water, at slow speeds!!

While I have messed up an acrylic blank or two sanding too aggressively, I've messed up more of them drilling the center. When drilling acrylic you have to be patient to the point of painful, make short stabs, and back out frequently to dump shavings that hold heat, melt quickly, and smear up/scratch the inside of the blank.


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## rdabpenman (Nov 25, 2017)

Drill at 250 rpm. Turn at 3500 RPM. Razor sharp tools with light cuts. Sand 400 grit only radially and laterally. Buff radially and laterally with Ultra Fine steel wool #000/0000 equivalent. Polish with Hut Ultra Gloss. Works great for me.

Les


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## Bean_counter (Nov 25, 2017)

Sounds like it could be chatter from your tools. Sometimes I get ridges on my blanks from hogging off to much


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## Herb G. (Nov 26, 2017)

I'll tell you what I figured out so far.
I drilled the blank slowly on my lathe. I cleared the swarf every 1/2" or so.
I checked the inside of the blank after drilling & it was uniformly dull inside.
In other words, no scratches or gouging inside the blank.
I painted the brass tube before using epoxy to glue it in.
The glue was allowed to dry for 48 hours before turning.

I turned it as close to the bushings as I could. I sanded it the rest of the way.
When I feel the blank getting warm, I stop & let it cool down.
Since it's only 60*F in my shop, it doesn't take long.
I forgot to sand it parallel to the length between grits.
I went back & did that, and got the scratches out.

I buffed it out with the Micro Mesh pads & finished it with One Step Plastic Polish.
The inside of the blank has a crack in it from casting. I believe too much catalyst was used in this batch.
The inner part of the blank has wrinkles or ripples in it where it set too quickly when poured.

It is too far gone for me to use in anything I'd put my name on, so it will serve to remind me that no plastic blank is perfect.
Here's a link for the blank so you know which one I'm talking about.
http://www.rockler.com/green-acrylic-acetate-pen-blank
Thanks for all the help guys. At least I know where to start looking from now on.
I appreciate it.


Well, a follow up, if I may.
I was sitting at my desk this morning with the blank in front of me.
I had not touched it at any time, but I heard a *CRACK*
& looked down to see the blank had delaminated itself from the brass tube.
It split along the length & peeled back like a banana.

I picked up the blank & most of the acrylic fell off the outside of the tube.
I painted the tube & let it dry for 24 hours. I glued the tube in the blank with 2 part epoxy & let it dry for 24 hours before I turned it.

My guess is that this blank had too much catalyst added to it & it dried way too fast, or it was poured in layers & it did not bond well.

Either way, the blank itself was definitely defective.


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