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Dave_Junior

Member
Joined
Apr 19, 2016
Messages
13
Location
New York, USA
I am still new to pen turning and just began turning acrylics. I am having an issue with getting a good surface after turning. The pen barrels have divots and other depressions that I can never seem to get out. I am using a brand new Rockler square radius carbide cutter tool to turn and cannot get a smooth surface. Anybody know what I am doing wrong?

Thanks,
Dave
 
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Dave, I don't use carbide tools, so that may make a difference. A lot depends upon the blank--I find that Inlace Acrylester is prone to this sort of problem. These days I pretty much just use a sharp medium-sized HSS gouge on all sort of acrylic blanks. I turn everything at full speed. I am very gentle until the blank is round, then I get a little more aggressive, backing off again once the blank is getting down to final size.

If you're unsure if you can get a smooth surface with the chisel, finish turning a bit proud of the bushings and finish up with paper--that's what I did for quite a while.

If you have ANY pits, they will not come out with Micro-mesh, so use 400 grit dry to get rid of them.

That's my recipe for acrylics, FWIW.

Regards,
Michael
 
You are probably too aggressive. Sneak up on it. tiny bites. Start from the end and barely barely touch and move the cutter.

I too have carbide cutters and I never use them on brittle blanks, wood or acrylic. As Michael does, I have my own made HSS gauge and I take a swipe across a 600 - 800 sandpaper every 30 seconds or so to keep it razor sharp. Quickness at getting to the finishing point is your enemy. Quickness at getting it rounded is your enemy. The point is a finished pen, and not how quick you can get there. Impatience is not noticed but it is there!
 
Thanks guys, I probably am too aggressive and wanting to finish the pen quicker then I should. Ill try taking it nice and easy and see how it goes.
 
Hi Dave, I use EZ carbide tools almost exclusively. I have had the best success with using the round cutter first and then when the blank is close to the size I may switch to the radius cutter with fresh edge to smooth up the surface if needed. Welcome to the very addicting hobby of pen turning.
Good Luck.

Rod
 
I use both HSS and carbide when turning acrylic. When turning carbide, I always turn at a much slower speed. simply because, the carbide tools scrape and do not shave like the HSS do. High speeds tend to chatter and eventually chip out the material. Much of my work is with a 1/2" bowel gouge and Ci2-R2 Radius carbide cutter and
Ci3 Round cutter. Hopes this helps!!
 
My vote is for a well sharpened skew. Learn how to use this tool and you will never have these problems again. Unless a blank has inherent divots in it due to the way it was cast, a skew will slice through that material. My opinion.:smile:
 
I only use carbide and find that turning the speed of the lathe higher helps with acrylics. Taking several shallow passes, rather than a deep pass will work better for brittle materials.
 
My 2 cents. I use EZ Wood carbide and turn at 3200 RPM using a gentle approach. I make sure the carbide is sharp. Using the Ci2-R2, one thing I discovered, if I get chatter, the blank is too far out from headstock or too much of the tool is contacting the blank. The tool also needs to be on center. I cut one blank at a time, meaning working on my patience and remembering to have fun and enjoying the experience.
 
I'm a rookie and I'm using the same Rockler square radius as you. I've turned 5 acrylics with the excelsior, see my avatar image. I had it at 2200 rpm and I found rolling the cutter to a 45 helped me slightly shave down any small divots. One of the Experienced turners at the store gave me the tip. You'll want to hold it steady and take a light cut.

Good luck.
 
Dave_Junior said:
I am still new to pen turning and just began turning acrylics. I am having an issue with getting a good surface after turning. The pen barrels have divots and other depressions that I can never seem to get out. I am using a brand new Rockler square radius carbide cutter tool to turn and cannot get a smooth surface. Anybody know what I am doing wrong?

Thanks,
Dave
Click to expand...

The SQUARE carbide cutter is very difficult to use as an all purpose cutting tool for pens. The 4 inch or 2 inch radius are a better choice...MUCH BETTER! The reason is the amount of control you have on your cut. The square cutter presents a broad cutting surface to the blank, which is prone to chatter and chipping of the material. Make that change along with the other suggestions offered, and you will be seeing great results. Happy Turning! :smile:
 
Some of the harder, more brittle acrylics are practically impossible to "turn" without getting the chipping you describe. The same material may also vary from blank to blank depending on how the hardener reacted with the mix / colors, and et cetera. It's unusual to find two blanks exactly the same. You may also encounter difficulty drilling some of these harder blanks without coolant and lubrication.

Sharp tools, high turning RPMs, and don't try to cut it down to size. Gently (that's sometimes difficult because some of these materials tend to get catches -- seems to grab your sharp tool and drag it into the cut) cut to an oversize. Then reduce your speed to 3-400 RPM and use 150 grit paper to take it down nearly to size. Then increase the grit of your paper to 220, 320, 400 til you reach your final dimension. Instead of pits, what you'll have is 400 grit scratches which you can work out with your finer micromesh.
 
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I used only carbide for pen turning. I start with a square insert to turn the blank round and switch to a radius insert for shaping. The last passes over the blank are very light with the cutter tilted at about 30 degrees. I usually then start sanding at 120 grit.
 
Turning help

I use carbide tools for acrylic. There is a couple things that you need to make sure of.
1. speed: You should be at high speed.
2. Tool rest: the tool rest needs to be very close to the acrylic. If the tool rest is to fare from the acrylic you will get chattering. That could be the cause of the divots.
 
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