a 1st time problem

[Richard Gibson]

I am a new turner. I have done 10-15 wooden pens and now I am doing acrylic. I have done 3-4 acrylics. No "major" problems as I learn, but today was a new one.

I was turning a piece of black w/white thread acrylic. From the beginning, it "acted" differently. There was a lot of vibration in the pice as I cut on it (but not while spinning by itself). When I would stop the lathe, there were flat places along the piece and small holes like it had chipped out. I continued to turn and ended up blowing out the lower piece. I finished the upper alright but still appears rougher than the other 3-4 that I have turned.

Any ideas or suggestions?

 

[its_virgil]

Exactly what material is it? Is the blank in question the same material as the others you mention? There are many many typed of "acrylic" pen blank materials and they all behave uniquely. What tools are you using? Some tools are a bit too aggressive for acrylics. The answers to these questions will help better answer your questions.
Do a good turn daily!
Don

I am a new turner. I have done 10-15 wooden pens and now I am doing acrylic. I have done 3-4 acrylics. No "major" problems as I learn, but today was a new one.

I was turning a piece of black w/white thread acrylic. From the beginning, it "acted" differently. There was a lot of vibration in the pice as I cut on it (but not while spinning by itself). When I would stop the lathe, there were flat places along the piece and small holes like it had chipped out. I continued to turn and ended up blowing out the lower piece. I finished the upper alright but still appears rougher than the other 3-4 that I have turned.

Any ideas or suggestions?

 

[PenPal]

Morning here from 6 thousand miles away with little or no knowledge of what, how, no pics
showing the means of holding. It sounds as if when you cut the blank is stalling, how do you face the ends, why do you turn at what speed, do you use a mandrel? Can you see if you ask first you must describe in detail having checked your lathe is in line accurate point to point and so on. Purchase at least one good treatise on turning pens. You could have a Club or turning group next door to you you give no info where you live, no name. To get a little you need to give a little.

Have fun learning show off your previous pens, show detail on this pen.

Kind regards Peter.

 

[KenV]

If you heard the dreaded "acrylic buzzzz" you know you are doing something wrong for that particular material -- and usually it is too agressive an approach, not super sharp tooling, or too much force especially near the ends.

I find some acrylics differer from one end of the blank to the other -- every one can be different.

I use a hunter round tool (carbide) on those which are the most troublesome instead of the standard skew -
Some days, a steep sharpend skew as a scraper is the answer (look at some of the Ed Davidson videos in the library (YoYoSpin).

 

[Richard Gibson]

Don- It is a "Lava Bright" acrylic from PSI. I got a sample pack and the others I have turned came in the same package. I am using a Woodchuck Pen Pro which is what I have used on all my others.

Peter- I am turning at 1700 rpm on a Jet Mini-lathe with a screw-on mandrel and a mandrel saver tail stock. The lathe is set accurately point-to-point. I just finished turning two other pens and it is still accurate. I don't know what a "treatise" is. I wish I could get a picture but I destroyed the bad piece when it blew and I took the rest off to save the brass tube.

As for my name, place I live, and pictures of other pens???... it's just to the left of each and every post.

Ken-thanks for somewhat understanding. I just cut and finished another acrylic pen this morning as well as an Olivewood one. This was my 3rd one this morning and it simply acted differently. It might be that I need to sharpen (turn the edge) on the Woodchuck but I don't think so.

Thanks for the feedback.

Richard

 

[Padre]

It sounds like chatter to me. That can be caused by the holding the woodchuck at an incorrect angle or having the tool rest too high or too low, usually too low, thusly taking out a bigger bite of the acrylic than you should. Those small "air bubbles" or the "things" that look like are bubbles are actually chunks of acrylic that have been 'chopped' off the blank. You should only get a smooth ribbon of acrylic using the woodchuck. Try changing the angle or the height of the tool rest and I think you'll have a much better result.

 

[ed4copies]

Hey Richard!!

Welcome to IAP and the wonderful world of Resin!!!

I believe Lava Bright is one of the acrylester series. This is a polyresin product that has beautiful colors, but is formulated to cure quickly to keep the colors separate, instead of blending (Yellow and blue turn green, given time).

What this means is the blanks are prone to be "chippy". My recommended approach is to remove the corners of square blanks on your sanding station, before mounting on the lathe. Then, I use a sharp skew in a near vertical orientation. Video here:
http://www.youtube.com/watch?v=LTgiE_U6eOk

The blank I am turning in the video is NOT acrylester, but it is a polyresin, that has a much more "turner friendly" mix--so it is far less likely to shatter. The technique is, however, the same.

Hope this helps, feel free to PM me if you have specific issues you would like to know more about.

 

[ed4copies]

Sorry, just read you are using a Woodchuck.

DEFINITELY remove the corners before you start. This is a very nice tool, but it works best when contacting the blank continuously. Use a different tool (IMO-you are allowed to differ) to get the blank to round, THEN the woodchuck will do a fine job of fine turning.

FWIW---I am NOT an expert with the Woodchuck!!!

 

[cnccutter]

Richard, it might not even be something you are doing. we think that all blanks from a given batch are the same but it just isn't so. if the person casting adds just a bit more hardener, or just a little less the acrylic blank can turn out much different. this even happens in bigger production casting shops.

As others have said/asked every acrylic blank turns different depending on if its PR or Aluminite. it sounds like you havnt had truble befor or after tis blank so I betting its more likely not you but the characteristics of that particular blank.

Erik

 

[Richard Gibson]

Thank you guys. I appreciate the feed back.

 

[okiebugg]

tailstock

FWIW, I've had the same problems turning acrylic at the slower RPM's.

One thing that hasn't been mentioned is the fact that your tailstock on that particular pen may have been held too tightly against the mandrel. I push the tailstock almost up to the mandrel and tighten lightly with the quill. If too loose, your blank will skip. If too tight, your mandrel will 'bow' thus making your mandrel deformed between the centers. The combination of the proper tension on the tailstock, combined with the raised RPM will probably help solve the problem.

 

[Akula]

remove hard edges, light cuts with sharp tools

 

[Richard Gibson]

FWIW, I've had the same problems turning acrylic at the slower RPM's.

One thing that hasn't been mentioned is the fact that your tailstock on that particular pen may have been held too tightly against the mandrel. I push the tailstock almost up to the mandrel and tighten lightly with the quill. If too loose, your blank will skip. If too tight, your mandrel will 'bow' thus making your mandrel deformed between the centers. The combination of the proper tension on the tailstock, combined with the raised RPM will probably help solve the problem.

Thanks but with the Mandrel Saver, there is no tension on the mandrel rod. All of the pressure is on the bushings. I adjusted it several times and still did not alleviate the problem.

 

[Richard Gibson]

FWIW, I've had the same problems turning acrylic at the slower RPM's.

One thing that hasn't been mentioned is the fact that your tailstock on that particular pen may have been held too tightly against the mandrel. I push the tailstock almost up to the mandrel and tighten lightly with the quill. If too loose, your blank will skip. If too tight, your mandrel will 'bow' thus making your mandrel deformed between the centers. The combination of the proper tension on the tailstock, combined with the raised RPM will probably help solve the problem.

Thanks but with the Mandrel Saver, there is no tension on the mandrel rod. All of the pressure is on the bushings. I adjusted it several times and still did not alleviate the problem.

I'm curious now Okiebugg. How fast do you usually turn acrylic?

 

[Richard Gibson]

Sorry, just read you are using a Woodchuck.

DEFINITELY remove the corners before you start. This is a very nice tool, but it works best when contacting the blank continuously. Use a different tool (IMO-you are allowed to differ) to get the blank to round, THEN the woodchuck will do a fine job of fine turning.

FWIW---I am NOT an expert with the Woodchuck!!!

Ed, thanks for your suggestions. I didn't realize who you were until I was re-reading these suggestions. I have been looking at your site for the last couple of weeks and getting ready to order a couple blanks to try. Love the stuff on your site but I want to get a little better before trying some of the really high price stuff and mess it up

 

[ed4copies]

Richard,

When you order, make a note in the comments---ask us to include a few "seconds of PR" for you to practice. They are likely to have bubbles when finished, but they make GREAT practice!!

 

[Richard Gibson]

Richard,

When you order, make a note in the comments---ask us to include a few "seconds of PR" for you to practice. They are likely to have bubbles when finished, but they make GREAT practice!!

Thank you very much. I will do that this week
Richard

 

[KenV]

I have one of Ken's carbide tools in the tool bucket and use it a bunch -- but it does not do the best job of turning on everything --

There are some materials that do not respond as well with the PenPro or similar tools as to a light cut with a skew, or to a cup cutter such as a Hunter tool.

Brittle acrylics may take a different tool or approach --- How do you know == Listen for the buzzzz of the chipping happening and plan to change. I can end up using a steep bevel skew as a scraper and high speed with light cuts when I get closer to avoid the chips.

Yup -- I have lost a few blanks along the way too --

I can sometimes tell during drilling that I will have a challenge --

 

[okiebugg]

RPM

FWIW, I've had the same problems turning acrylic at the slower RPM's.

One thing that hasn't been mentioned is the fact that your tailstock on that particular pen may have been held too tightly against the mandrel. I push the tailstock almost up to the mandrel and tighten lightly with the quill. If too loose, your blank will skip. If too tight, your mandrel will 'bow' thus making your mandrel deformed between the centers. The combination of the proper tension on the tailstock, combined with the raised RPM will probably help solve the problem.

Thanks but with the Mandrel Saver, there is no tension on the mandrel rod. All of the pressure is on the bushings. I adjusted it several times and still did not alleviate the problem.

I'm curious now Okiebugg. How fast do you usually turn acrylic?

Usually between 2500 to 3500 RPM. Very sharp tools (Usually a skew). I rough pens with a 3/8" Sorby bowl gouge and almost always finish at the higher speeds with of all things, a 5'8" Sorby Carving skew. This skew is sharpened like all of my tools by hand on a regular Delta grinder with no special wheels. The skew is ground slightly into a small radius for better results. The skew allows me to turn a flat surface by eye or feel with little or no chatter.

Anymore, I don't turn much acrylic or other man made plastics because a Dr. friend ordered 35 pen and pencil sets at Christmas for his employees and friends. "All to be turned out of wood" I asked him if he wanted any Set turned out of anything else like acrylic. I got a very interesting answer. "If I wanted pens made of plastic, I would have bought them cheaper at Office Depot". Ponder that statement when making decisions about what to make your retail pens out of.

 

[JohnU]

Something else to pay attention too since your using a mandrel saver tail stock... Make sure your mandrel saver is not resting on the threads of the mandrel. This will cause much chatter and uneven turning. Been there done that. Took me a bit to realize but after I slid it up on the smooth rod I past the threads I was fine.