"Exotic Blanks" Are Chipping Heavily When Turning

[jacobbaldwin]

Hello, everyone! I'm fairly new to pen turning and have recently purchased some pen blanks from exoticblanks.com to use in crafting fountain pens. When turning these blanks on the lathe, using a carbide-tip roughing tool OR a carbide-tip finishing tool, big chunks are spontaneously breaking off. Rather than get a relatively smooth surface from which I can sand and polish, I get a peppered surface covered with holes and gashes. I've been turning hardwood prior to these with the same tools with no issues. I'm wondering if RPM has something to do with it, but I'm not certain. Currently I'm using about 1000 RPM on the lathe. Can anyone inform me why this is happening, and how they recommend turning these blanks so that they are smooth?

Thanks,

Jacob

 

[DrD]

What blanks specifically? AA (acrylic acetate), Inlace Acrylester, Rhino Plastic, Tru Stone, etc? A heavy cut, eg heavy hand may cause what you're seeing. A faster - but not much faster - speed may help, eg 1800 rpm; some suggest as fast as your lathe will go. Obviously how you are presenting your cutting tool yo the spinning blank. EZ Wood recommends a level approach slightly above the midline of the spinning blank. The sharpness of the cutter - all these can result in deeply pitted surfaces.

Log on to ExoticBlanks website and "Pour yourself a cup of coffee and enjoy
Exotic Blanks Pen Turning how-to videos!" Ed covers a lot of this and more. They are very good, very short, and very helpful.

Plus you'll get lots more tips here at the IAP.

 

[Sly Dog]

First, if I were you I would feel totally comfortable contacting exotic blanks about it because they will know the material you ordered and help you pinpoint the problem. Excellent company; knowledgeable and responsive.

It would be helpful to know the material you were turning. Some "acrylics" are more brittle than others and thus more prone to chipping. Other factors can include tool sharpness or dullness, the pressure you exert on the blank from the tool, turning speed, and even temperature (from what I've read). There are lots of older threads about brittle materials and chipping you can find by searching.

 

[qquake]

It can happen with any acrylic, but is more prone with the brittle blanks, especially inlace acrylester and Rhino. It happens to me a lot, because I have an aggressive turning style. I tend to get impatient and try to take off too much material with each pass. All I can do in these cases is force myself to back off and make less aggressive cuts. Lately I've been using a homemade carbide chisel with 15mm radiused cutters (2" radius). But instead of holding the cutting edge parallel to the blank, I rotate it to a 30-45 degree angle. I find this gives me a more "shearing" cut. But in spite of all my tools and turning techniques, the most important thing for me is to be patient and take lighter cuts. Oh, and I turn at around 2000 rpm.

The photos of my chisel are for illustration purposes only, and are not indicative of the "proper" way to use a carbide chisel. Merely to show you what I mean by a shearing cut. You'll need to practice and play around with different techniques to see what works for you. I recommend practicing with Rhino blanks (Exotic has a crap ton of them!). They're more brittle than say acrylic acetate, but less brittle than inlace acrylester. They're also very inexpensive, and Exotic will often have specials on certain Rhino blanks.

 

[jttheclockman]

Lets start with the speed, yes crank it up if you can but only you will know what a good speed is for you. Everyone is different. But 1500 to 1800 is good. The tool, you say carbide roughing gouge. What is that??? Is that a square blade carbide tip tool?? I do not like using those because you can have too much material in contact with the blade at one time if you lay it parallel to tool rest. That is not a good turning technique. The round cutters are a good tool to do the roughing with and finish off with a nice sharp skew. That is the tools I always promote. The skew is the best tool in the turning arsenal. Learn to use it. Next is the speed of feed rate of tool. You need to go slow and not too fast when bringing the tool across the blank. Faster will cause the blank to chatter and cause the pitting you see. You need to let the cutter do the work. This goes for the amount of pressure you apply to the tool also. The more you try to hog off at one time will cause above problems. Light cuts and slow tool speed will get you there. Takes practice when working with acrylics of any kind. Some blanks are more brittle as was mentioned but all material is turnable even the most brittle blanks. Hand eye coordination is key feel the tool do the work. One last thing make sure your equipment is good quality and running top notch. By this I mean there is no misalignment in head stock to tail stock on the lathe. The method you use to hold the blank weather using a mandrel or not is straight and true. Any bent rod will cause the blank and tools to skip causing said pitting. I always like to keep the mandrel as short as possible thus I always turn one blank at a time. You have to turn them one at a time anyway so why set both on the mandrel together. Never could understand that. Good luck and practice.

 

[alphageek]

Welcome to IAP and welcome to acrylics. Acrylics (of which is a generic term for over a dozen type) have their own learning curve. I recommend upping your speed (I use the top of my lathe at 3000 rpm. I also suggest that you watch some of Ed's videos https://www.exoticblanks.com/How-To-Videos.html Ed has some and I know one of the newest on their is Mark has one for turning acrylics with carbide tools. Ed and Mark both have years of experience and thousands of pens. It's a great place to learn.

 

[WriteON]

I'm a fan of high speed and a sharp skew from start to finish. Slow approach and light passes. Acrylics are sensitive to catches. And all acrylics are different. You'll get the feel. It takes a few times. Hang in there.. and welcome to IAP............... edit: work on short blanks for now.

 

[walshjp17]

I generally turn most resin-based blanks (acrylics, epoxies, urethanes) at 3200 - 3600 RPM and use very sharp skew chisels or negative rake carbide cutters. I use light passes, especially while the blank is still square-ish, and stop often to clear the ribbons (mostly to see what I am doing). Your mileage may vary, but I have not had much chip out since switching to NR cutters.

 

[turnit2020]

You are having the problem that most folks run into when first trying acrylic type blanks. The old adage sharp tools and light cuts is a good one to follow. I turn a lot of acrylics and have found that a lathe speed between 1600 to 2200 is best for me. I now use the Easy Wood negative rake cutters with all acrylic blanks regard less of type. Some folks turn with the round finisher cutter in negative rake and others, like me, use the R2 negative rake rougher. I cut at the midpoint of the blank and level. The negative rake cutter has given me the best cuts with any type of acrylic materials and produces far less chips. You will determine your best approach with practice and sadly with mistakes. A previous responder pointed you to Ed at Exotic Blanks for videos and advice. That is great advise. Keep practicing and you will get much better.
Turncrazy43

 

[ed4copies]

Sunday is "no rush" day, so I am just seeing this.

For a frame of reference, Jacob purchased "stardust" blanks which are exclusive to ExoticBlanks. They start out round, so this cannot be a "rounding" problem. They are manufactured in Italy and, as close as I can tell, they are a polyresin. More difficult than RhinoPlastic but
no where near as chippy as Inlace Acrylester.

There is a video (from 2013) showing how to cut with a 3/8" gouge, you can see it here:

In 2015, I made one on Easy Wood Carbide (pre-negative rake), cutting a resin that is similar to Stardust, which you can see here:

And, to listen to a DIFFERENT voice, watch the recent video from Mark Dreyer on turning "Plastic" with the Carbide tools:

I would suggest getting a few Rhino Plastic blanks (there will be a couple on special in the Sunday email). Get comfortable turning those and the transition to Stardust will be easier.

Welcome to IAP Jacob!! Hope this helps you and others!!

Ed

 

[ed4copies]

I don't know this demonstrator (FrickWerks), but this video is a pretty good commercial for the negative rake cutter, cutting another blank that looks to have similar characteristics to Stardust:

 

[ramaroodle]

I too would suggest a negative rake scraper or at least a faster speed and a less aggressive turning approach.

 

[qquake]

Hey Ed, have you ever considered having a rating system for your blanks based on turning difficulty? It would make things easier for beginners/novices.

 

[ed4copies]

Thanks Jim!

Yes, I have considered it and think it is a good idea--just have not gotten a "Round tuit".
Also considered doing a video on each type of material, another "Round tuit" needed.

They are both GOOD ideas that should be implemented!!!!

Ed

 

[qquake]

That would be thousands of videos! And then what would you do for one-off blanks?

 

[ed4copies]

I believe you have pinpointed part of the problem.

 

[jttheclockman]

Another problem is every batch of acrylic blanks may not be the same. If they are made by artisans they may have over cooked them with too much catalyst. If it is a foreign country made you have no idea what the material is and again not all turn the same. Too many unknowns to have a rating system in my opinion. Yes certain materials just are natural pains and we all know those or you can list them easily. To me the problem is operator error. Eventually if you want to become a pen turner per-se you need to be able to read the material you are turning as soon a s a problem or different occurrence happens. Plain and simple. The solutions brought up here about speed, tool presentation, tool choice and light cuts apply to each and every blank you turn. Turning some plastics even more so as well as with metals of all kinds. There are plenty of videos out there and plenty of threads on this topic so the info is available. We all have been through it and hopefully you learn as you go. Hands on experimenting can not be beat. This is a proven fact in whatever we do in life. Good luck and happy turning.

 

[qquake]

I agree with John, for the most part, and maybe a rating system isn't realistic. But you could certainly list groups of blanks for beginner, intermediate, and advanced.

 

[PaulWitmer]

Hi Jacob:
Welcome to the IAP. Following up with what everyone has stated above, turn at a higher speed, take light and easy cuts and use the rounded tip for finishing. Additionally, you need to be comfortable with your lathe and tools in order to minimize any presentation challenges. With a lot of craftsmen all over the globe all providing different formulations of a acrylics, alumilite and other resins, it is important to take light cuts. It will save you grief in the long run and you will gain experience with various makers' products. I use both carbide tipped tools as well as the standard HSS steel turning tools an rarely run into these type of occurrences as I did when I started out turning. I learned a long time ago, that haste with acrylics and resins, will definitely make waste of some blanks.
Paul

 

[jacobbaldwin]

Thank you to everyone for the awesome advice! Happy to know that IAP is an active and informative forum for this hobby. I am pleased to say that implementing a few recommendations produced stellar results when attempting to turn the remainder of the 'Stardust' blank that Ed sold me to the diameter I'm needing. Big shout-outs to those who chimed in with the following advice:

• Setting the tool rest below center of the blank, and approaching with the carbide tip roughing tool at a slight upward angle to produce more of a cut rather than a scrape.
• Increasing RPM - I set my RPM to about 2500 and the cuts were smoother and there was minimal, if any, chipping/shattering on the edges when taking easy passes without forcing it too much.

Attached you should see a before and after comparison... You'll see that things are looking A LOT better. (Note: I cut off the portion you see in the 'before' image, thus it is so small..

Thank you again!

-Jacob

 

[ramaroodle]

WOW! "Our work here is done!"

Now you can help pay it forward by posting what works best for you, as you learn. Your technique will turn out to be unique in some way.

If you can crank that puppy up to 3k rpm, try that.

 

[egnald]

Great progress - Congratulations! - Dave

 

[qquake]

Another thing I do with acrylic blanks is to "knock" the corners off. Makes them easier to rough round.