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Acrylic problems

Joined
Jan 24, 2010
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Nothing major but gave me less than a quality turning. My grandson turned an acrylic piece for a pen for his mother (I helped him and he did about 85% of the work with me helping guide the tools). I noticed when we were done with the major turning to round, there were spiral grooves in the blank. We started with a roughing gouge, rounded the blank and then went to a spindle gouge. I sharpened the gouges and noted that there was a slight dip on the wing (?) of the cutting edge of the spindle gouge. Is this the culprit? We sanded with 320, then 400 wet and then the wet micro mesh pads. Still had a few small tool marks left. I wasn't happy with the outcome but my wife said that our DIL would be pleased that the boy made it. I would like to hear from the forum about preventing this in the future. I have several pens to turn for Christmas gifts. Yes, starting early.
As always, thanks in advance for taking time to look and for your replies. 🙂
BTW, I plan on getting a Wolverine sharpening jig. It seems I can't go to the Woodcraft store and not spend some $$$$. 🙄
 
Just a guess ... that sort of sounds like the spindle gouge was used with the cutting edge touching the acrylic, but the bevel wasn't rubbing. That sort of condition can cause chattering which is what your description sounds like. Other possibilities might include a dull tool and too much pressure being application to get the tool to cut. Were you getting long streamers or chips?
 
I think you arrived at success. The next one will be a success too.
I have only turned a few pieces of acrylic. My experience is that it is important to ride the bevel.
The dip may be bringing the edge off the bevel.

It is also possible you are moving the gouge too fast across the pen. This will leave ridges in sort of a spiral pattern when I do it, but I suppose it could leave grooves too.

My suggestion on the next one is to turn it just round with the roughing gouge then make some smoothing cuts with the spindle gouge while you have some material to remove.
Be sure to ride the bevel and not rush the cut. You want to go fast enough to have a continuous shaving coming off but no faster.
Play a game with your grandson to see who can get the longest thread in one pass.
 
You may have applied too much pressure on the bevel of the gouge, and deflected the pen mandrel. Also could be moving the gouge too quickly along the part. If you don't have a perfectly smooth cylinder, 320 is too fine to start. A skew is the perfect tool for pens.
 
Thanks to all. I have several pens to turn before Christmas. I can get lots of practice with wood and acrylic. I had sharpened the spindle gouge and the roughing gouge then touched it up with a DMT diamond mini-file. We did get long threads of acrylic. We had to stop and clean them off the mandrel periodically.
Now, to a definition- could you clarify what you are meaning by riding or rubbing the bevel? I might be using just the cutting edge of the spindle gouge but not using the proper angle to approach the cut. Again, thanks! Is there a good Youtube video you would recommend?
Might stop at a cabinet and countertop shop and see if I can score some Corian for practice.
 
... Now, to a definition- could you clarify what you are meaning by riding or rubbing the bevel? I might be using just the cutting edge of the spindle gouge but not using the proper angle to approach the cut.

Are you familiar with the ABC rule?
A = Anchor the tool to the toolrest with the back of the tool handle low so that the tool isn't contacting the wood
B = Bevel -- raise the back of the tool handle to lower the tool until the bevel is making contact with the wood, but the cutting edge still isn't make contact
C = Cut -- continue to raise the back of the tool handle until the cutting edge just begins to create shavings. This is the angle that you want ... the cutting edge is removing wood and a portion of the bevel adjacent to the edge is riding against the wood to support the cut. If you were to continue raising the back edge of the handle any further the bevel would lose contact with the wood and the tool would start chattering and scraping.

I think that John Lucas has a video on this topic.
 
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Bill gave a great description.
It is also the cut that is close to coming out of the wood and not cutting.

With practice you get a feeling for the bevel.
When the bevel is locked in the tool sort of cuts by itself with no effort on the part of the turner.

One of the keys is to hold the tools loosely.
A turning tool is like any game played with a stick you hold the stick loosely.
If a six year old can't pull the bat out of your hands you can't hit with it.
 
Bill gave a great description.
It is also the cut that is close to coming out of the wood and not cutting.

With practice you get a feeling for the bevel.
When the bevel is locked in the tool sort of cuts by itself with no effort on the part of the turner.

One of the keys is to hold the tools loosely.
A turning tool is like any game played with a stick you hold the stick loosely.
If a six year old can't pull the bat out of your hands you can't hit with it.

Now that you mention being relaxed, I remember when I was first learning to turn I was about as stiff as a statue with a death grip on the tool. One of David Ellsworth's videos included some limbering up exercises to get you thinking about moving your body almost as if you were dancing with the lathe. Before that I was rigid except for my hands and wrists
 
The other variable is the acrylic, depending on the compounds mixed into the acrylic some of
these materials can be a pain to turn, a really sharp tool helps with most of the issues. Some
of these compounds added to acrylic blanks can quickly dull a sharp tool.
 
A lot has been revealed in posts 6, 7 and 8. It sounds simple, but sometimes things are lost in translation. I would suggest reading the ABC post again and visualize each step. Nothing wrong with mounting a piece of round scrap wood on the lathe and slowly turn by hand while going through the ABC’s as Bill stated. So, you follow the ABC’s, the tool is cutting, shavings flowing, life is good… and then the tool starts getting twitchy, a little catchy, the cut isn’t as good, the shavings turn to chips, what happened? Sometimes, when things are going well, the handle drifts up, which means the cutting edge drifts down, which also means the bevel has come off the wood and the tool is now scraping. Lower the handle. If things are going well, and you lower the handle a tad, the tool should stop cutting, if it doesn’t, you were off the bevel. Back up and start over with the ABC’s. And as Al said “loose”… let those tools breath…

cc
 
Thanks. I got the idea. Will practice as I have enough wood to build a small cottage.

Dance with the lathe? We Baptists aren't supposed to dance. Our pastor refers to it as coordinated movement. 🙄
 
BTW, I plan on getting a Wolverine sharpening jig. It seems I can't go to the Woodcraft store and not spend some $$$$. 🙄

There are a couple accessories for the Wolverine. One is the Varigrind jig. I highly recommend the original Varigrind and not the Varigrind 2. The other accessory is the skew sharpening jig. I don't know if others use it, but mine only came out of the box once or twice to look at it and then hasn't been touched in the last dozen years.
 
Bill, the one I'm considering is Woodcraft #125676. Might add #125677 later on. Are these the items you refer to?
 
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