"Bubbles" in acrylic/synthetic

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Woodchipper

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I recall seeing a thread that addressed this issue and neglected to Favorite it. I have a blank that is full of them. Not exactly bubbles but pock marks in the material. I read the thread and said, So that's what causes it! I had couple of places today that had minor issues and I had enough material to carefully, with light touches, turn them down. Can anyone help here? What am I doing wrong? Not sure what to use for search words. As always, thanks.
 
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Tim'sTurnings

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I try to make sure and mix the liquid material slowly and I try my best to not make bubbles in the first place before putting the blank/s in the pressure pot. That is what helped me a lot when I make PR blanks and also make sure you have a consistent pressure in the pressure pot until the blanks are hardened.

I have read on this forum and have done it myself that you can fill in the pock marks in the hardened blanks with CA. It might take more than one application to fill the holes.

I wish you the best of luck Woodchipper. I am sure you will get other options/suggestions from other forum members that may help.
Tim.
 

Woodchipper

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This is not a casting. It is a camo blank from Woodcraft. I'll try to post a picture but not confident it will be decent.
 

duncsuss

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That's chip-out (the plastics equivalent of tear-out), the blank is more than likely solid.

A few possibilities for why this might be happening ...

... tool vibration, blunt gouge, blunt scraper, blunt carbide insert, lathe rpm too high causing the tool tip to get hot, trying to take too large a bite, too much pressure (rubbing the bevel too hard against the blank) ...

Approaches to reduce/eliminate the problem ... sharp tools, less pressure, move the tool rest closer to the blank (to reduce overhang and chatter due to vibration), slow down the lathe rpm.
 

MikeinSC

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Either your blank is vibrating, a dull tool, too much pressure or you're cutting too fast.

I catch myself all the time doing one of those things when it happens to me. It is usually, in my case, a dull edge and pushing it a little too much. Or it's vibrating and not tight on the lathe.
 

Woodchipper

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May be all of the above. I have my grinder two steps from the lathe so keeping my tool sharp is not problem. I think I might have been using a round nose scraper. BTW, I did an acrylic blank today and decided to try a 3/4 roughing gouge. When my grandson took a pen turning class, the instructor used a one inch roughing gouge and was fantastic with it. A real craftsman, and not one from Sears. I came out with a much better first-finish and easier to sand and polish.
Will be aware of what is being said here. I do get into a rush sometimes and have to back up and slow down.
Thanks to all.
Edit: Now all I have to do is figure out what it was for, find the bushings and finish turning it.
 
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Beautys_Beast

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I use a large roughing gouge to do exactly that, rough out my blanks. Light passes. Works wonders. If I get to aggressive, it will chatter. It's the blank talking to me, saying patients grasshopper. I shape with a skew, and finish with a small carbide skew.
 
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Woodchipper

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Found the cause of the dimples!

I was taking a break and was looking for info on sanding and finishing acrylics and synthetics. I stumbled onto Exotic Blanks and found a video on turning acrylic. Ed showed how this hiccup happened- I found that I had pushed the gouge into the blank for some unknown reason. He showed the difference in pushing the gouge into the blank and cutting along the long side of the blank.
 

ed4copies

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I was taking a break and was looking for info on sanding and finishing acrylics and synthetics. I stumbled onto Exotic Blanks and found a video on turning acrylic. Ed showed how this hiccup happened- I found that I had pushed the gouge into the blank for some unknown reason. He showed the difference in pushing the gouge into the blank and cutting along the long side of the blank.
These posts are ALWAYS appreciated!!!!

Lots of time went into making those vids, it is good to see someone benefit--THANKS for mentioning it!!!

Ed

For those who may not know, there is a library of videos (over 70) FREE to view, here: https://www.exoticblanks.com/How-To-Videos.html

You will also get there, if you "click on" my signature box.
 
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