I keep blowing out the acrylics

[BigguyZ]

Hello-
I'm new to this forum and pen turning alike. Last night I was trying to turn two different acrylic blanks, but got the same result. One was a pink acrylic from Rockler, and that one seemed really quite brittle. I don't know if it was me or the blank, but it was impossible to get a smooth but on that. The second was one from Woodcraft, and cut like the other blanks I've turned. But for both of them, I'm having difficulty not getting a large amount of chatter while turning the acrylics. It seems like every other blank I turn ends up in shards. I've tried doing different cuts with different chisels, and nothing is working consistently. I'm also not sure what speed (RPM) I should be turning at.

Do any of you have any guidelines? I looked in the articles section, and couldn't find anything specific.

Thanks!

 

[its_virgil]

Fast speed and use a skew. Take a look at the videos in the library by Ed Davidson, aka YoYoSpin. I don't use the skew the way Ed does, but it works really well and Ed is an excellent turning instructor and his videos are also well done. I find gouges to be a bit agressive. You could round them with a disk or belt sander and then use a round nose scraper.
Do a good turn daily!
Don

Originally posted by BigguyZ
<br />Hello-
I'm new to this forum and pen turning alike. Last night I was trying to turn two different acrylic blanks, but got the same result. One was a pink acrylic from Rockler, and that one seemed really quite brittle. I don't know if it was me or the blank, but it was impossible to get a smooth but on that. The second was one from Woodcraft, and cut like the other blanks I've turned. But for both of them, I'm having difficulty not getting a large amount of chatter while turning the acrylics. It seems like every other blank I turn ends up in shards. I've tried doing different cuts with different chisels, and nothing is working consistently. I'm also not sure what speed (RPM) I should be turning at.

Do any of you have any guidelines? I looked in the articles section, and couldn't find anything specific.

Thanks!

 

[BigguyZ]

So you're saying I should take orr the corners with a sander prior to moving to the chisels? I'll try that. I'm not huge on using the skew- it seems to e my #1 chisel for getting massive cathes with. It's probably my technique, but for now it's definitely not my favorite...

 

[Jeff-in-Indiana]

even if you are not a Level-5 Skew Ninja, haha, you can still use it like a scraper and get where you want to be ... "sharp, sharp, sharp" is how you the skew should be sharpened. "fast, fast, fast" is how the speed should be .. "light, light, light" is the type of cut you should be taking ...

The great videos from YoYoSpin (Ed Davidson) are excellent at illustrating how-to ..

It would be useful to grab a hunk of junk wood and practice your skew technique ...

 

[its_virgil]

There was a thread here a couple of months back (I think) about this very topic. It showed a jig for reducing the acrylic blank to almost finished diameter then completed with a scraper. Using a scraper is slow but works. Using a skew as a scraper may be a little faster. Using the sanding jig should go much faster. Watch the Ed Davidson videos and search for the sanding jig for acrylics. Keep practicing...it will happen.
Do a good turn daily!
Don

Originally posted by BigguyZ
<br />So you're saying I should take orr the corners with a sander prior to moving to the chisels? I'll try that. I'm not huge on using the skew- it seems to e my #1 chisel for getting massive cathes with. It's probably my technique, but for now it's definitely not my favorite...

 

[babyblues]

Even if your technique is correct you won't get good results with a dull tool. Sounds to me like it's not sharp enough. Dull tools aren't going to cut the way they should, and it's going to take more pressure to do any cutting at all which causes more heat and stress on the material.

 

[Texatdurango]

Travis, When I started turning acrylics I was having the exact same results you are, tossing away I don't recall how many blanks because they just kept chattering or broke off chunks of plastic.

The turning point in my success was watching Ed Davidson's videos then re-watching them then watching them again to see what he was doing that I wasn't. Things finally sunk in and now I use a skew with no problems.

I echo the comments about using a light touch, regardless of what tool you use, it's important to use a sharp tool and don't get too agressive. It still takes me a lot longer to turn an acrylic blank than a wood blank.

Some say sanding the edges is a waste of time but if you are having trouble with the tool catching the blank, anything is worth a try until you get more proficient. Heck, I actually found that using a scraper worked for me. It took forever but at least I was making pens![]

George

 

[Chasper]

I've been there an made the same mistakes. But I've been successful with the last several acrylics. Turn the speed up high, sharpen chisels well and often, don't be overly aggressive, and it makes a world of differance. Using a skew properly makes it even better. I haven't pre-cut or sanded the corners.
Gerry

 

[RONB]

I am making my own acrylics and find that sanding down with an angle die grinder with a 36 grit pad works for roughing in. Then it's a sharp skew, fast speed and cut it like it cost a million dollars. Slow and steady works for me.

 

[Narwhale]

Think most of us started out with flying acrylic shards.
Now, for me, the acyrlics and PR blanks turn better and faster than wood. Learned to:
1. Crank up the lathe speed to high (really, all the way.)
2. Sharpen the skew.
3. I use an old HF 3/4" skew to take off the corners. Small cuts, gentle. I don't push the skew into the work, but let it cut along the top surface.
4. When the skew is rounded, the skew should be taking off nice long, light fluffy strings that wind around everything. Little tiny cuts. Easy does it.
5. Shape with the skew till close to correct shape.
6. Switch to newer skew that is sharp and clean up shape. Will use this skew as a scapper to get smooth finish without any lines or continuous marks. It may still have some chatter marks, but otherwise smooth. Get ends level with bushings.
7. Slow down lathe to 300 rpm and start wet sanding with 100 or 220 grit paper. Sand wet thru 1000 grit, wiping balnks off between grists. Then on to micro mesh (MM&gt
Hope this helps.
Rich S.

 

[BigguyZ]

OK, I had actually slowed down the lather because I saw a online supply store state to not turn at excessive speeds. I have the Jet Mini lathe, and I think right now I'm turning all the blanks at a very low speed. Maybe 900-1200 RPM. I'll go back up to full speed. I also read just today that over tightening the brass nut cat create a wobble in the mandrel- and I've actually been seeing that lately. So I'll ease up on that too.

I think a major issue is the quality/ sharpness of my tools. I have the HF HSS set, and a couple my dad gave me. One's a large Sorby gouge, and another a diamond parting tool. I'm having a heck of a time getting a consistant bevel, and I'm actually not sure if I'm doing it correctly. To sharpen, I'm using a belt loop sander from HF. That's what the guy from The American Woodshop used, and I figured it'd be easier and cheaper than a whole slow speed grinder + wolverine+ whatever set up. I think I may need to be pointed in the direction of a resource to help me sharpen correctly.

In the mean time, I'll up the speed and do my best with what I have. I have two acrylic pens due tomorrow from commissions...

Thanks!

 

[leatherjunkie]

I have the lathe set to the same speed that i turn wood blanks, fast fast.

I will glue up my acrylic blanks and let them sit overnite before attempting to turn em. this has helped me in not having the acrylic blanks blow apart on the lathe.


I even use my 3/4 roughing gouge to turn my acrylics. after the acrylic gets close to the bushing size i will switch to my skew.
I use the skew like a scraper and do the final shaping. this smoothes up the blank and helps with sanding. then i just sand to 2000 gritt sandpaper. use the sandpaper dry till 400 gritt, wet sandpaper at 600 gritt to 2000 gritt. then i use the buffing system to finish the blank.

this works very well for me.

 

[Narwhale]

BigguyZ,
Your profile says you live in Minneapolis Minnesota.
.
There ought to be someturning clubs or groups up there, see if you can take you tools there and let them show you how to sharpen some of them.

Anybody here from there
?
rich s.

 

[BigguyZ]

Narwhale- I should definitely try that. Eventually I want to get into turning bowls/ etc, so I'll need all the help I can get. In the mean time, I'm thinking of using the Woodcraft slow speed grinder that's currently on sale instead of the belt sander I'm currently using. I might get better/ more consistant results with that. I'm still looking into my options.

But, given all that, I was back in the saddle last night, and everything went really well. I had one tool slip and chip out a small section of one acrylic, but I used super glue to repair it, and it's virtually invisible under the clip. Other than that, I turned two acrylics from scratch, and turned another to final shape from round. I'd post pics, but either the forum doesn't support that- or more likely, I don't have that function yet b/c I'm new.

Thanks everyone for the help! I still need improvement, but my confidence is back up after destroying $9 worth of blanks the day before.

 

[PatrickTaylor]

I too have the Jet mini (6 speed non VS) and I like to use the second to highest speed (2500 rpm I think) for wood and acrylic pens. I turned to near-finished shape with the spindle roughing gouge, then either use the skew taking light cuts or use the wing if the roughing gouge (riding the bevel and addressing the piece at about 45 deg towards the direction I'm cutting.. this makes a cut similar to but not as smooth as a skew... it's also more forgiving!)

That's my method, YMMV. []

 

[KenV]

You may want to note that Ed Davidson (who turns lots of plastic) sharpens his skew at a considerably steeper angle (less bevel/bezel) than is traditionally used by those who turn wood (e.g. Alan Lacer). For Ed, the length of the bevel is about the thickness of the skew. For Lacer examples, the bevel length is about 1 1/2 the thickness of the skew.

Shorter bevel will result in a stiffer edge and combined with keeping the tool rest really close will reduce vibration/chatter. Honing with a diamond stone will also result in a finer edge than you will get from most grinding wheels and also result in less vibration.

Get some low cost blanks and practice practice practice --

 

[BernieW]

BigguyZ check your e-mail. I use a skew all the time on mine. They must be extremely sharp. If I feel it getting a little dull I will hone it with a diamond hone. If you are having trouble with the skew get Alan Lacer's "The Skew Chisel". Excellent video. Unless you are accomplished freehand sharpener I would definitely recommend the wolverine jig. A skew will give you a surface that just needs to be micro meshed.