Carbide Tools for Turning Acrylic Blanks?

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thawkins87

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May 15, 2017
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So I just recently got into pen turning. I made a few cool pens from exotic woods and tried my hand on an acrylic blank (I believe it was an inlace acrylester blank). Once I got the blank to round and started turning it down, I noticed my carbide tools were essentially just "chunking out" pieces of blank instead of pulling off in ribbons like it shows in all the videos I watched.

I guess my question is, can you use carbide tools to turn acrylics, or have I unknowingly committed a faux pas? If most people don't have a problem with carbide tools and acrylic blanks, is there something I'm doing wrong? Any tips, etc? I use my round cutter on most things, and this particular blank i tried turning at probably 1000 rpm or so.

I ended up being able to salvage the blank by turning it to shape plus about 1/8" on the radius or so and sanding it down for an hour, but I'm not keen on repeating that process...

Thanks!
 
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lyonsacc

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Hi Tim,

A couple of thoughts:

1) inlace acryluster gives a lot of people trouble. Seems to be one of the harder acrylics to turn. But the results can be very pretty.
2) I would try a higher rpm - maybe in the 3,000 to 4,000 range
3) carbide works fine on acrylic - but you need to have sharp cutters. Some folks on the IAP replace their blades every couple of pens, others, like me, sharpen the cutter every couple of pens. They are pretty easy to sharpen.
4) glad you could salvage the blank. I have sanded down a few because I was afraid of a chunk or a blow out. But sanding down for an hour seems awfully long. Maybe up your grit of sandpaper (I would start with 150). With acrylics make sure you wet sand (keep the blank and paper wet with plenty of water) rather than dry sand. And maybe up the RPMs as long as you can keep the blank from getting too hot.

Hope that helps.
Dave
 

mecompco

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Dave covered it pretty well! I never slow my lathe down for any pen material--wide open at 3700 all the time (no idea why folks slow them down). IA is probably the worst acrylic to turn--hard and chippy. I use an R2 cutter in my Magical Skew. The Magical Skew's shaft is a hexagon, so it makes it easy to hold at an angle to the work piece, like you would do with a HSS skew. I'm sure you could do the same with your tool. IA prefers to be cut rather than scraped. I am frugal (wife says cheap), so sharpen my cutter with diamond cards.

If you're still getting chipping when your getting near the final diameter, there's no shame in switching to paper. You might, while you are learning acrylics, want to switch to one that is easier to turn (which is pretty much any of them).

Regards,
Michael
 

moke

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I only turn acrylics for pens and aside from true stone, inlace acrylester is one of the most difficult.....
I totally agree with mecompco, there is no shame in going to sanding earlier than you might ordinarily. Do what you must to get a good product! I might try using the "corner" of the cutter. This is similar to what a metal lathe would be doing....rather than scraping. Scraping "stresses" anything, and chipping is a result. As mentioned, keep your cutter sharp. The diamond file is the best, or just turn it in it's mount.

You can sharpen the cutters many times, except I once mentored a guy who insisted on setting his tool on the lathe and continually knocked it off. Carbide is brittle and chips...turn the cutter head to get rid of the chipped side and always set the tool where it can not be knocked off.

I would recommend picking up a 1" skew chisel, watch some You tube videos on how to use it and practice on 2x4's cut to 1 1/2 square. It takes some practice but the skew is an awesome tool. You can even scrape with it, if you must .... Once you get the hang of it, you will not use your carbide insert tools much.....
All just IMHO.
 
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campzeke

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All good advice in the above posts. I use carbide for all of my pens. Wood, acrylic, antler, and Inlace. I can turn most acrylic blanks in 10 minutes or less. Inlace ... that's another story. I usually turn at 24~2500 RPM... it works for me. When turning Inlace, I use very light cuts and will often sand the corners off on a belt sander before turning. I will almost always spend 2 to 3 times longer on an inlace blank than almost any other type. It's worth it in the end but it does require a little more patience in the process. The same is true of the Stars and stripes blanks many vendors sell.

As a new turner, I would recommend staying away from Inlace until you are more comfortable with some of the other acrylics out there. Work on your fit and finish first. Focus on smooth, tight joints where the blank meets the kit hardware. Work on your sanding and polishing procedure then apply what you learned and ease back into Inlace.

Bottom line, don't get discouraged and let's see some photos of those beautiful pens you are creating!
 

thawkins87

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Awesome - thank y'all so much for the tips/advice. I suppose it was just a bit unlucky that I grabbed one of the harder materials to work with the first time around; I'm glad I asked the question or else I would have assumed that all acrylics were as difficult!
 

Edgar

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All great advice - I can't really add much except to suggest that you try an R2 cutter. I find it easier to control and get the contours that I want on pens than a round cutter. I use my round cutter for some of my bottle stoppers & other spindle shaping, but when I just want a straight or slightly contoured shape, an R2 works best for me.

I also agree with Mike, cant the R2 cutter about 30˚ or so rather than presenting it straight on. I just have a regular square bar on mine, but I have no problem canting it to and holding a steady angle with it. A hexagonal bar like the Magic Skew does make it easier though.

Definitely high speed & sharp tools. I generally turn pens around 3000 RPM.
 

qquake

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I hate inlace acrylester, and rarely turn it. When I do, I always use sandpaper for final shaping, starting with 100 grit. This money blank is either inlace acrylester, or turns just like it, and I hated it. But my friend was set on a pen with it, so I persevered.
 

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eharri446

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I turn a lot of IA. I use a 3/4 inch Sorby spindle gouge and my round carbide. In some instances, I turned the corner round using a mill file. I also stop a little proud of the final dimension and take the rest of the way with Abranet. I usually start with 80 and go to 600, then I wet sand it using 500 and 1000 grit then finally I switch to MM and go from 1500 to 12000. That put a finish on it that can stand on it's own, however, I use sometype of plastic polish to complete the process. Now that I have a R2 carbide I will be using it to do some of the final turning.
 

TonyL

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Inlace, Acrylester, and other more brittle "plastics" motivated me to use a sanding jig to trim barrels and HSS skew to turn. I also turn those materials at 2,500 rpms. I have used carbide, but have personally had more success with HSS. I turn it all the time now. Much success with your process!
 
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So I just recently got into pen turning. I made a few cool pens from exotic woods and tried my hand on an acrylic blank (I believe it was an inlace acrylester blank). Once I got the blank to round and started turning it down, I noticed my carbide tools were essentially just "chunking out" pieces of blank instead of pulling off in ribbons like it shows in all the videos I watched.

I guess my question is, can you use carbide tools to turn acrylics, or have I unknowingly committed a faux pas? If most people don't have a problem with carbide tools and acrylic blanks, is there something I'm doing wrong? Any tips, etc? I use my round cutter on most things, and this particular blank i tried turning at probably 1000 rpm or so.

I ended up being able to salvage the blank by turning it to shape plus about 1/8" on the radius or so and sanding it down for an hour, but I'm not keen on repeating that process...

Thanks!
Easy Wood Tools had a carbide insert for the tools that has a negative rake cutting edge that eliminates the chips and catches that can occur when turning acrylic or composite blanks. They work amazingly well. If you do not have the EWT tools, try tipping the handle end of your tool up in the air at about a 20 degree angle and raise your toolrest just above center. Also, I would turn at a higher rpm. Hope that helps!
 

donwae

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I use the 'negative rake' cutter from Easy Wood on acrylics and other man made material. They work better than any thing else I have used.
 

robutacion

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Australia - SA Adelaide Hills
I was going to mention the carbide with the negative rake inserts but Don already did that.

I have read a lot of comments about these inserts and people that turn hard acrylics and hardwoods and they seem to have resolved the issues they were having.

Negative rake tools is not a new thing, I remember to have created the negative rake shape in some of my gouges many years ago so is great to see that carbide insert makers have also developed that shape/design on some of their inserts, they are not impossible to sharpen but I wouldn't bother, they are not that expensive, any more.

Cheers
George
 

randyrls

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Late to the party; I normally have no trouble with IA (I just ordered some and Karma will get me!:)). Just use the tool below center and peel off endless ribbons. You can't "hog off" material this way, a light touch is needed. My goto tool for acrylics is the lower one below; presented below center.

The negative rake scraper can be used, but it just changes the geometry of the blank to tool contact point.

 

Sylvanite

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Hillsborough, North Carolina, USA.
IMO, carbide scrapers are popular with penturners for two reasons:
  1. You don't have to learn how to sharpen your tools.
  2. You don't have to learn how to do a shearing cut.
Once you have learned how to sharpen and use a HSS skew chisel, however, carbide scrapers don't work any better. I have an EasyWoodTool carbide scraper, and while it is a well-made, high-quality tool, my preferred chisel for almost all penturning is my cheap 1" flat skew with a rounded heel (hollow-ground HSS).

Only once have I ever felt I needed to use a carbide cutter for a pen, and that was when turning Petoskey Stone. The stone was so abrasive that steel tools wouldn't hold an edge.

By all means, use whatever tool you like, but I believe that investing in your skills yields a better return in the long run.
 
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