Turning Acrylis

[danroggensee]

Hi all is there a trick to turning Acrylis I tryed my first one today and it blowout rignt at the end of cuting so I thought I may have but to much pressuer on it so tryed another one and the same thing. I know I need to keep my tools sharp. is there someting else I can do to stop this other then stop earlyer and sand to finsh

Dannie

 

[GouletPens]

You're right about the sharp tools, and you're also right about the pressure. You don't want to push too hard, especially near the end when the acrylic is very thin. If you use epoxy as the glue, it can help fill any voids between the brass and the acrylic which will help with that problem as well. The more you do, the better you'll learn the "magic touch" you need when working with them. They're second nature once you've done a few.

 

[Jim Smith]

I also find some acrylics much more brittle than others. Some turn like butter with long curls and others seem to come off in tiny chips. On the brittle ones I take it really slow and switch to sanding (wet on acrylics) much earlier than with wood or some of the softer, less brittle acrylics. I also suspect that some of the very hard acrylics have small cracks that are just waiting to blow up on you no matter how careful you are. It's like the old children's rhyme. When they're good, they're very, very good, but when they're bad they're very, very bad. Dont' give up, they're certainly worth the effort.

Jim Smith

 

[chriselle]

Dannie,

Try to imagine the cutter on a metal lathe. Rest your finger against the tool rest and control your cuts in a smooth, controlled, balanced motion. Don't rotate your tool during the motion.

YOU control the tool...it doesn't control you.

All this basically translates to is light passes and patience.

Sharp and I mean SHARP! tools are a gimme.

 

[ldb2000]

First I have to ask what tools are you using to turn these acrylic blanks and what speed are you turning them at . For me I use a 3/8" carbide spindle gouge for rough turning to just above the bushings then switch to my 1/2" carbide oval skew and a shearing cut to the bushings then switch to a scraping cut to final size . Using this method I almost never have a blow out and can start sanding at 320 , and I turn all acrylics at full speed .

 

[Greg O'Sherwood]

For me I use a 3/8" carbide spindle gouge for rough turning to just above the bushings then switch to my 1/2" carbide oval skew and a shearing cut to the bushings then switch to a scraping cut to final size .

I couldn't have said it better myself! No blowouts yet, but it does take me 20 minutes to do a slimline like this, so it is slow...

Gregory of Sherwood Forest

 

[Nick]

I do the same as Butch except my tools are not carbide and I use the 1/2" to 1" oval skew to do the final cuts after getting it round with the gouge. Light and slow cuts with a very sharp tool. I use a credit card diamond hone on the skews.

 

[Mather323]

On real brittle acrlyics when using a skew I have had much better luck cutting into the acrlyic at the end. I have blown out a few then I have used my skew and started cutting in at one end and kept going until I got to the other end and cut way at that end and that is where my blow out occured.

 

[TellicoTurning]

After watching Ed Brown, (ed4copies) at a demo in the MPG a couple years ago, I do almost all of my turning on acrylics with a skew... usually a 1" flat skew (because I don't own an oval one - mine is from a cheap set I got with my original lathe from Home Depot), then for detail, I'll switch to a 1/2" flat skew... I rarely use any other tool on acrylics. Since I watched Ed's demo, I've blown out very few blanks... unless I get impatient and too aggressive in my cuts.

I'll use the spindle gouge to round over an antler blank, but switch to the skew as soon as I'm close to round.

 

[ed4copies]

Thanks Chuck!! Nice to know someone heard me!!!!

 

[wdcav1952]

After watching Ed Brown, (ed4copies) at a demo in the MPG a couple years ago, I do almost all of my turning on acrylics with a skew... usually a 1" flat skew (because I don't own an oval one - mine is from a cheap set I got with my original lathe from Home Depot), then for detail, I'll switch to a 1/2" flat skew... I rarely use any other tool on acrylics. Since I watched Ed's demo, I've blown out very few blanks... unless I get impatient and too aggressive in my cuts.

I'll use the spindle gouge to round over an antler blank, but switch to the skew as soon as I'm close to round.

Ed turns acrylics??????????????

 

[jimbob91577]

Ed - do you have a video in the IAP library demonstrating this technique? I haven't started to turn Acrylic blanks yet, but considering I often turn spirals with my skew, perhaps watching someone do it once or twice would be a good thing.

Thx!

 

[scotti158]

SHARP Skew, light pressure

I also use a skew for acrylics, going from square to just above bushings with the same tool. As you've already read, it works best when sharp, if my skew won't shave the hair on my arm, it gets sharpened on my Makita 9820-2 planer blade sharpener.

 

[danroggensee]

Thanks guys for all tip will try it again and let you know how it goes.


Dannie

 

[MobilMan]

Dannie, I may not be the tool or pressure that's the problem of the blowout. It could be the drilling. If the bit 'wanders' as it's starting to bore the hole, you'll end up with a slightly oval hole--not round-- for the first 1/8" or so. Cut you're blanks & drill, but insert the tube from the other end & try not to have the tube reach that first drilled part. Normally the end the bit exits will be round. This 'oval' will cause you to cut thru the blank thickness & be a blowout. Good luck

 

[Rcd567]

Just getting started myself, but found penturning extremely frustrating until I switched from CA to epoxy for glueing my tubes in. Didn't matter, wood or acrylic, both would blow up leaving a lot of the brass tube exposed. After reading on this site about using epoxy, I haven't had a one. (dives for wood to knock on while typing this) I know I'll have an occasional one but it was really frustrating at first.

Make sure you use epoxy. I use 5 minute but don't usually turn them until the next day. I would guess a couple hours would be good enough. Hope this helps others from the frustration I experienced.

 

[ed4copies]

RCD: If your avatar is a "self-portrait", you don't look too frustrated.

 

[JohnU]

Epoxy made the difference for me. Also, I keep my acrylic blanks in the house and not in the basement shop. Downstairs they get cold and seem to shatter or get more brittle when turned cold.

 

[TellicoTurning]

Make sure you use epoxy. I use 5 minute but don't usually turn them until the next day. I would guess a couple hours would be good enough. Hope this helps others from the frustration I experienced.

As the mobilman said, do watch your drilling... my cheap HF DP sometimes has a wobble in the bit if I'm not careful with how I set the bit in the chuck... I've gotten the oval starts on my drilling... I've always cut my blanks long to accommodate this, but since switching to the lathe do do my drilling I have much fewer incidents of the oval hole.

I rarely use epoxy..just thick CA and have little problems from the glue... after I started using the skew, turning plastics got a lot easier. I'm very generous with the CA when I'm gluing.. generally will insert the tube from both ends with a twisting motion and make the final set on the cleanest end(meaning the one that's either not oval or doesn't have a chip out which you can get if the bit isn't sharp or I go through the end too fast without some support under the exit)

 

[Dr. Frank N. Stein]

Chuck,

To use the lathe to drill did you buy the barracuda head to hold the blank?

but since switching to the lathe do do my drilling I have much fewer incidents of the oval hole.

if not how are you doing it. If I don't need it would like to get rid of the drill press I thought I would need. Even with it's fancy lazer gadget.

Thanks,
Mike

 

[ed4copies]

You can drill on the lathe with a scroll chuck and small jaws (I use #1)

OR pin jaws

Or Beall chuck (If you pre-round your blanks)

 

[randyrls]

To join the thread; I always rough up the brass tubes before gluing them in. The brass has something, (lacquer?) on it that prevents a good glue bond. This makes it easier to remove glue from the inside of the brass, but you want a good bond on the outside.

 

[TellicoTurning]

Chuck,

To use the lathe to drill did you buy the barracuda head to hold the blank?



if not how are you doing it. If I don't need it would like to get rid of the drill press I thought I would need. Even with it's fancy lazer gadget.

Thanks,
Mike

I just use the barracude with pen jaws or my little cmg3c chuck...

 

[eck]

try this link,. great stuff
http://www.penturners.org/forum/showthread.php?t=316