Acrylic blank chipped failry badly.

[HoleyDiver]

Hello,
As title states acrylic blank chipped. First time turning acrylic blank. I was using carbide tools. All was fine while turning with square cutter but once I switched to round I started getting pits and then then this big chip broke off. Any guidance or advice would be very much appreciated. I am very new to turning. That k you very much.
JB

 

[egnald]

Hello,
As title states acrylic blank chipped. First time turning acrylic blank. I was using carbide tools. All was fine while turning with square cutter but once I switched to round I started getting pits and then then this big chip broke off. Any guidance or advice would be very much appreciated. I am very new to turning. That k you very much.
JB

Was the blank perhaps an Inlace Acrylester or perhaps a Rhino Plastic blank? Those are two of the most brittle "acrylic" blanks that I am familiar and are prone to being "chippy". They are also therefore some of the most difficult plastic materials to turn. They require very sharp tools (like the carbide that you were using) and light cuts. A negative rake cutter is really the best for these as it is less aggressive. I've had the best luck cutting these at the highest speed my lathe will go. If you still get major chips you might try sanding it down to the final dimensions.

Inlace Acrylester is a polyester resin based material. I think Rhino is polyester also, but perhaps with different additives and/or percentages of hardeners that affect the brittleness.

I think the easiest to turn, but more expensive are they urethane based blanks, like Alumilite (and less odiferous as well). I would certainly recommend Alumilite blanks for beginning turners.

Although Inlace Acrylester is a tough material to turn, it polishes great and makes great looking pens. I don't turn it very often anymore and opt for Rhino blanks instead as they are a little less brittle but still polish great.

Here is a link to the help sheet .pdf file for working with inlace acrylester from the owner of the trademarked material, WoodTurningz. Link: Working with Inlace Acrylester. Although your material may not be Inlace, the information in the help sheet should still be pertinent to all brittle plastic blanks.

And of course, the best of luck to you! - Dave

PS. If you can find the piece, you might be able to glue it back in and salvage the blank.

 

[1080Wayne]

I find it is too easy for me to get aggressive with the round cutters , so now use the square ones for chippy blanks . As Dave said , use your highest lathe speed .

 

[its_virgil]

Acrylic is one type of plastic or resin. Acrylic is not a generic term for any and all types of plastics or resins.
Do a good turn daily!
Don

 

[RKB]

I use carbide and the Negative Rake Cutters are awesome with the plastic type blanks.

 

[Penchant 4]

Also, take care to be sure that the tool rest is set so that the edge of the cutter is not higher than the centerline of the long axis of the blank.

A catch with the cutting edge above center will tend to pull the cutter into the material, whereas a catch with the cutting edge below center will tend to push the cutter away from the material. Not a guarantee, but a bit more insurance.

Good luck!

 

[ed4copies]

Everything above is pretty accurate.

IF you have the equipment to turn between centers, you can leave the tailstock a little loose and the blank will stop when you are not turning at the correct angle. Can be frustrating if it keeps stopping, but saves money on "trashed" blanks!

 

[Painfullyslow]

All of the information above is correct however looking at the blank itself it looks like it was cured with tons of little air bubbles in it. That is the only way to get those marks, especially if you were using a round cutter.

I am far from an expert here but I would call that blank as mis-manufactured and/or defective.

 

[ed4copies]

All of the information above is correct however looking at the blank itself it looks like it was cured with tons of little air bubbles in it. That is the only way to get those marks, especially if you were using a round cutter.

I am far from an expert here but I would call that blank as mis-manufactured and/or defective.

Sorry, you would be dead wrong.

I have created that same pattern hundreds of times in 25 years--doesn't matter what tool, it is possible to turn it incorrectly.

Air bubbles, by the way, will be round and are VERY RARE in pen blanks.

This may help make the situation clearer: (Video posted nine years ago)

 

[NGLJ]

So far as long as I take light cuts I have had no problems with Acrylic blanks using Easy Wood carbide negative rake square cutters with 2" radius. With the exception of a thin HSS parting tool, that is the only cutter that I use for all my pen turning. Of course if you want to make concave cuts then a round cutter would be needed. NR would still be the best.

 

[jttheclockman]

Carbide tools will cut very fast so need to take real light cuts and to work inward from the ends toward the center. I would also switch to a well sharpened skew for final passes to get rid of any dips and valleys. Just a matter of practice. Never have I blown an acrylic blank up and have turned them all. learn to feel the touch of the tool. Be in tune with it. Your fingers can tell when something does not feel right. I agree those are not air bubbles. Acylics can do that depending on hardness of blank and type of blank but easily taken out. Practice practice practice.

 

[jrista]

Hello,
As title states acrylic blank chipped. First time turning acrylic blank. I was using carbide tools. All was fine while turning with square cutter but once I switched to round I started getting pits and then then this big chip broke off. Any guidance or advice would be very much appreciated. I am very new to turning. That k you very much.
JB

From my experience, blanks that look like that were turned too aggressively. Resins, just about any except maybe acrylic itself (you can be pretty aggressive with true acrylic...it streams off in threads or ribbons...although if you go too darn aggressive it will start to have problems as well, in my experience it will "ripple" and cause chatter before it does anything worse...so you have a warning sign), will start to "shred" when you turn them too aggressively. This is particularly true the harder the resin is, but not exclusive to hard resins. When I first started turning resins, I was often too aggressive, pushing my tool in too fast, and the result was exactly this: chipout, which is what leaves those little voids or can even give you an obsidian-like surface, and can result in larger chunks being ripped from the blank.

If you see this starting to happen, the only solution I know of is to back off, and use lighter cuts. You can further soften the cuts by using negative rake cutters on carbide tools, or even by going with sheer cutting which puts the cutting edge of any tool at a sheer angle to the blank, which is even less aggressive and allows the lightest of cuts once you learn enough control.

 

[Humongous]

Definitely light cuts and slow down. It may be frustrating but I typically take 2-3 times longer to turn a plastic blank as opposed to wood.

 

[Painfullyslow]

Sorry, you would be dead wrong.

I have created that same pattern hundreds of times in 25 years--doesn't matter what tool, it is possible to turn it incorrectly.

Air bubbles, by the way, will be round and are VERY RARE in pen blanks.

This may help make the situation clearer: (Video posted nine years ago)

I appreciate the education.

I guess I am fortunate then that I have never seen a blank look that way and was trying to wrap my head around how it would be possible with a rounded tool.

 

[KenB259]

This is a no brainer, but since it did happen to me once, I'll throw it out there. Make sure your cutter is tight.

 

[David350]

As previously mentioned, when you see long ribbons of material coming off, you are usually doing well. If you see what appears to be dust coming off, this is bad and I usually see the "pitting" on the blank as in your picture...

 

[RobS]

its a polyester blank not an acrylic. Acrylic is exceptionally forgiving in comparison to a polyester blank.

So I second/third or forth the use of a negative rake carbide insert on polyester blanks.

Good luck.

 

[greenacres2]

I appreciate the education.

I guess I am fortunate then that I have never seen a blank look that way and was trying to wrap my head around how it would be possible with a rounded tool.

Definitely heat & pressure. Been there, bought a drawer full of t-shirts. For ME, the cause of the heat & pressure varies from size of cut, not recognizing dull carbide, hurrying, impatience, ignorance of some or all of the above. Again, my experience only--most people get smarter in less time than i ever will!!
earl

 

[farmer]

To me It looks full of air pockets,

 

[jrista]

To me It looks full of air pockets,

Definitely not air pockets. Air bubbles are usually perfectly round, and usually pretty solitary (unless, I guess, you used alumilite without pressure...but again, the bubbles would generally be round). I get the exact same effect if I am too aggressive with the tool. Note how the "pockets" are elongated, rather than round? Kind of the telltale sign of a too aggressive tool.

 

[farmer]

Definitely not air pockets. Air bubbles are usually perfectly round, and usually pretty solitary (unless, I guess, you used alumilite without pressure...but again, the bubbles would generally be round). I get the exact same effect if I am too aggressive with the tool. Note how the "pockets" are elongated, rather than round? Kind of the telltale sign of a too aggressive tool.

Thanks for the education.