Chipping issues

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Big

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Remember that I have been away from the addiction for the past 7 years. I have to get a sharpening rig for my tools too. That was at the top of my list before I had to step away and now that I am doing pens again, it is more critical than ever to get one and set it up. I can get new cutter blades for my carbide tools but I have to get a sharpening rig ASAP.

That being said, I wanted to ask something that I have experienced on the last couple of acrylic blanks that I used. The blanks were at least 7 years old and possibly older before I got them. My tools need to be sharpened very badly. So, the issue was a bit of chipping. Instead of getting the lovely ribbons of material as I was turning them, it was often more like a dust. I was turning them at about 1800 rpms too. The purple slimline chipped very badly at near the tip and was done to the tube. I had to use CA glue and some of the dust material to fix it which was extremely hard. But, you can barely tell that I had that huge "chip out" by the tip. My wife loves it because the colors are so amazing in this blank. It was an Acrylester material.

The Music pen had a few chipping issues too but I was pretty much able to sand them out. The colors in this Music blank are beautiful in my opinion. I usually like to trim them down so that they are a bit slimmer but because of the chipping and powdering issues that I was having when trying to turn these, I decided to leave them a bit fatter than I like. They are still pretty but not to my liking.

Any ideas about how to fix these problems when I do Acrylester or other acrylics moving forward?




Purple Acrylester Blank.jpeg


Purple Acry Blank 2.jpeg



Music 1.jpeg


Music 2.jpeg
 
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Turning acrylics is much smoother at the highest speed possible. It may seem counterintuitive, but it makes the experience easier. Also, with acrylester especially, turn from the outside of the blank to the inside - go from the bushing inward. That gives the most support to your cuts.
 
Acrylester makes gorgeous pens but it is difficult to deal with. You may want to look at some of the other types of materials too. I've not made any of my own so I can't comment on that but I know that I've enjoyed making pens from alumilite because it's so nice to turn.

Yes, sharp tools will always help you. Tremendously so. Same to be said for turning at a higher speed as thewishman stated.

Another option may be to look at negative rake carbide for non wood based turning also.
 
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I've stopped working with acrylester unless forced....lol....because of what you experienced. Using carbide tools with negative rake inserts, going easy with my cuts and turning up the speed of the lathe to the highest speed you feel safe will all help make this less painful. It's doubtful you will get 'ribbons' like with Alumilite, but it should give you something other than 'dust'.

Good luck!

Kevin
 
Being away for as long as you have, there have been many many new threads added as well as lots more info added to the library and has been reorganized so easier to track. I suggest you do some searching because many of these issues have been had by many members here and discussed. But to your situation now, you hit the nail on the head. Sharp is needed. As far as a tool for this I have the Tormax sharpener system but mostly use my grinder with white stones on them. It is a slow speed grinder which is what you want. getting the proper angles is key too. There are web sites that can help there because not everyone presents the tools the same way so trial and error comes into play there. Negative rake scrapers seems to be used alot. I have not tried them. My go to tools are always take down any blank of any material with a round carbide cutter. Then I always switch to a very sharp skew. I finish every blank that comes off my lathe with the skew. Also one last suggestion and you may have forgotten this tip but when turning any blank down it is best to turn toward the center at all times. It prevents chip out on the ends. There is more support of the material in the center than the ends. Good luck.
 
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The best points have already been made. Acrylester does make gorgeous pens, but it is really chippy. Negative Rake Carbide has served me well. For a long time I avoided Acrylester and opted for Rhino Plastic blanks, they have many of the benefits of Acrylester, (hard and polish well), but are a little less brittle and are a little more friendly for turning. The easiest of the "acrylics" would be blanks made from Alumilite - it turns almost like wood and produces the lovely ribbons you spoke of. - Dave
 
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Polyester resins seem like they will crack if you look at them the wrong way, but it polishes up better than the softer, smoother cutting ones. Drilling is quite a challenge, too, as you probably noticed. Alumilite is great to turn, but I end up putting a CA finish on it to get the nice glossy finish.
 
I rarely get chipping since I started using my square carbide tool like a skew. Everytime I go back to using it straight I get chipping
 
I will offer a contrary view. The chipping / breakage has two possible causes.
1. Chipping is caused by the force applied to the blank. If you present the tool bit ABOVE CENTER of the blank, you are "prying" the cut is pulling the material outward. Negative rake bits just make sure the cutting edge is actually pushing inward. The easier solution is to present the cutting edge BELOW center. If you are getting "nits", these are the chips you are pulling out. Note: The further below center you go the more aggressive the cut and the more force is applied to the blank.

2. The blank cracked when the drill bit "broke through" the end of the blank during drilling.

PS. I have a 5" 80 grit flat disk on a face plate to attach to the lathe. I bring up the tool rest and hold half the blank against the outer edge of the wheel to knock the corners off square blanks. This also reduces the shock to the blank.
 
sorcerertd said:
Polyester resins seem like they will crack if you look at them the wrong way, but it polishes up better than the softer, smoother cutting ones. Drilling is quite a challenge, too, as you probably noticed. Alumilite is great to turn, but I end up putting a CA finish on it to get the nice glossy finish.
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Oh yes, drilling can cause blowouts on the end. This almost always happens to me despite drilling slowly and not too aggressively. Knowing the likelihood of blowout forces me to mark the blanks wider than normal so that I have extra when the blowout happens and the tube will still be completely covered.
 
I think you've already identified that sharp tools are the #1 most important thing for getting smooth cuts in acrylic.
 
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