Pen "Chip Out"

[rickbw]

I have been casting pen blanks using Poly Resin from Douglas and Sturgess. I am really pleased with the colors I have been able to achieve so far. I am utilizing the round ice "cube" singles available for sports drinks to cast individual blanks. They work very well.

However, I have run into what I would call a "chip out" problem. The blank tends to chip out when I get close to end shape for the pen. I am using a sharp skew (similar to Ed Davidson's video) to shape the pen blank. Taking small cuts and being patient.

Could this problem be caused by the number of drops I am using to cast the resin? I am using approx 7 drops per ounce. Should I be using less?

Thanks in advance.

 

[turned_for_good]

When the chip out occures, are you cuting twords the center of the blank or away?

 

[rickbw]

It has happened a couple times, but I cannot remember which way the skew was moving. I want to say moving toward the end, but not for sure.

 

[ed4copies]

Originally posted by rickbw
<br />I have been casting pen blanks using Poly Resin from Douglas and Sturgess. I am really pleased with the colors I have been able to achieve so far. I am utilizing the round ice "cube" singles available for sports drinks to cast individual blanks. They work very well.

However, I have run into what I would call a "chip out" problem. The blank tends to chip out when I get close to end shape for the pen. I am using a sharp skew (similar to Ed Davidson's video) to shape the pen blank. Taking small cuts and being patient.

Could this problem be caused by the number of drops I am using to cast the resin? I am using approx 7 drops per ounce. Should I be using less?
Thanks in advance.

I believe it depends on temp and humidity while you are casting, but off the cuff, I'd say try fewer drops and see what happens.

And, cut from the outside toward the middle to help, while "rolling" your skew (takes a while to develop this technique). If you don't "chip out" acrylester-your method should work on anything.[][][]

 

[mrplace]

Also, use extremely sharp tools and turn faster than normal.

I get some really brittle casts occasionally in the summer when it is hot in the shop. I stopped trying to adjust the catalyst when I found out the blanks cut so much better at maximum speed on my lathe, that and using sharp tools.

 

[johnnycnc]

Originally posted by rickbw
<br />
I am using approx 7 drops per ounce. Should I be using less?

Thanks in advance.

I'm not the resident guru,but have done a good bit of casting.
I generally go 4 drops/ounce no more than 5.
I do cast indoors,controlled temp/humidity,so those
are not variables for me but could be for you.
My casts are a little brittle,but tolerable.
(I have used commercial castings and found some to be
almost so brittle as to be beyond my patience levels.)
Ed4copies advice on technique is probably most important.
Your mileage may vary []

 

[mick]

Rick as Ed says a lot depends on temp and humidity...but I've had my best castings when using the ice trays by using 3-4 drops of catalyst. It's usually overnight or at the least 6-8 hours before you can strip the molds, but you end up with a not so brittle casting. This helps with drilling as well as turning. To echo what mrplace says max speed and scary sharp tools are best for turning PR.

 

[Mikey]

7 is more than enough. It will harden with less and I do believe that is part of your problem. Also, do turn at a high speed with very sharp tools. Not everyone can use a skew for perfect results, so try a gouge or some other tool to use. You may find that one works better for certain medium than another.

 

[Gary Max]

Or---------when you get about 80% done removing the unwanted material---stop---- apply a couple drops of thin CA---let it sit for a couple of minutes---and you are good to go.