I am starting to get into turning acrylic pens. The problem I'm having is pitting. part of the pin blank when I'm finished sanding and buffing there are little pit marks on part of the pin tube. Any suggestions?
I don’t have a ton of experience by have made plenty of mistakes. If it were my pen it would be what Doug pointed out, chipping of the blank. Guessing that because pits are irregular shape (not casting bubbles) and kind of in a band around the pen.
I tend to get these if I change angle slightly while turning either as I shape the blank or move my hands. Things that help me is to “ride the bevel” of my Skew more as I get close to the final shape and move my body instead of my hands/arms as I move across the blank.
If you are using carbide (which I have less experience at) try more of a cutting angle and not a scraping angle. Some resin does not like carbide as well so lighter, angles cuts.
Also try to keep the cutting edge at or above the centerline of blank. This happens more with inlace acrylister vs AA. You can clean the blank well and fill the pit with a drop of medium to thick CA and let it dry. Skim with A sharp tool and re-sand and polish.
In my very limited experience, all of the above advice is spot on. The type of acrylic and tool used may be helpful for more precise advice. As many have said, when I get those pits it is typically too aggressive of a cut...I'm not very patient and want to see the finished pen too quickly!
If when you turn you hear what sounds like ripping and getting covered in tiny chips or flakes instead of long ribbons of plastic you are too aggressive, using dull tools, presenting the tool wrong and stuff that isn't coming to mind. When you get it right the barrel will be smooth requiring very little sanding and the shavings will be like fine ribbons or hair. Practice with inexpensive blanks turning, them to nothing, that you don't care to make a pen from.
Only living across Indy from WoodTurningz I started out on Inlace Acrylester. Glad I had a face shield on. First few I thought ripping the corners off in a rain of shrapnel was the way it was supposed to work. Then watched some of Captain Eddie’s videos on sharpening, read some things on here about turning IA and now love it, normally turning the entire thing from square to finished with a sharp Skew. Though I can now use carbide to finish (just because the guys at WoodTurningz said not to try using carbide on it). Beautiful shine.
Some great advice has already been given, but nobody has mentioned that sometimes acrylics are just crappy to begin with.
Either they had too much catalyst added when they were poured, or they set up too fast, or it was too cold to set properly or, or, or.
I turned some AA blanks & they just delaminated all by themselves.
One was sitting on my desk when it went *POP* and split away like peeling an onion. I had turned it a few days before, so it had been sitting for a few days when it did it.
I still have no idea why it did it, it just did it all by its self.
Have turned both of these blanks (7/8 from PSI) and the 3/4" from Exotics. Never saw air bubbles in either one. They did not seem brittle at all. I agree with others the problem may be need for sharp tools and small cuts.