bad plastic for threading??

[watch_art]

Well, I turned two sections, and the same thing on both. Several cracks on the threaded bit of this plastic:
Bear Tooth Woods - Invisavue UA-01 Black Pen Blank

Is this stuff just not good for threading?

Here's one of my sections...

 

[watch_art]

here's the back end.

 

[SDB777]

I think your turning the inside threads firtst, correct? Then screwing in something to 'support' the blank while turning the outside threads?

Maybe the 'support' is too large and once the material is removed on the outside, it's just enough to allow it to crack....




This is just a guess....cuase I really haven't seen your set-up.





Scott

 

[watch_art]

It's really frustrating b/c I'm doing the same things with this as I do with the smaller sections and I haven't had any cracks like this. I've squished a bunch of super glue in the cracks and will chase the threads to see how it does. Ugh...

 

[leehljp]

Another way of saying what Scott said - is that it is better to thread the outside first, put some kind of a support cap on it, and then thread the inside.

Different PR has different characteristics so the technique and sequence of threading become VERY important.

I have not done this, only reading the different posts on this as I intend to start doing the kit-less in the near future. (I hope I got it correct.) There was another thread on this very subject just a few days ago.

 

[watch_art]

IT's not PR though - it's acrylic. I'll go ahead and do the support collar though - for the next section (making three of these).

Thanks

 

[leehljp]

IT's not PR though - it's acrylic.
Thanks

OK, that doesn't make any difference in the results - because from what I have read, PR or acrylic act the same in threading. The "sequence" is what is important at this point.

 

[Dan_F]

I've net tried threading this material, but I do know that as even though it seems relatively soft, it dulls my skew pretty fast, so it might be harder on taps and dies too. Might not be the best material for sections, and I'd be even more leery of using the triple starts on it for bodies for that reason.

Dan

 

[watch_art]

Thanks. Just using single start threading....
I'll probably end up making black sections from acrylic. Dernit.

 

[soligen]

I tried this marterial too and it is not near as friendly as the regular acrylics. My results were similar to yours. I used up the 2 blanks I bought and never tried it again.

It is more opaque than normal acylic. To do this, I think they have to add more pigment, which affects the workability of the material. I've also struggled with black acrylic, which is more opaque than the normal arcylics. My conclusion is that more pigment means less workability

 

[watch_art]

Hmmm.... interesting. THanks! Guess I'll avoid this stuff in the future then. Black delrin or even black ebonite would be the way to go I guess?



Source for black delrin?

 

[Texatdurango]

Well, I turned two sections, and the same thing on both. Several cracks on the threaded bit of this plastic:
Bear Tooth Woods - Invisavue UA-01 Black Pen Blank

Is this stuff just not good for threading?

In my opinion, Alumilite, being polyurethane, is by far the best material for making sections. Compared to the more brittle plastics, acrylics, and whatever else they are called, the polyurethane is more forgiving in that it will give more before it cracks. I think it was Curtis who tossed an acrylic pen and an alumilite pen up in the air, one breaking, the other bouncing! That pretty sums up the difference.

I've made and sold dozens upon dozens of pens with Alumilite sections and haven't heard any complaints but have received several positive comments about the feel.

To me, Ebonite has a soft warm "grippy" feel, acrylic has a hard cold "slippery" feel and Alumilite falls in-between.

On Edit: I just saw your last post and I would NOT use delrin, it is way too soft and while it is nice to work with, the customers will scratch and mar it to pieces!

 

[soligen]

George,

Do you use the black alumilite, or add pigment to the clear?

 

[watch_art]

Alumilite huh? Thanks! I do like that stuff quite a bit. Very easy to work with. I also saw the video of throwing the alumilite and acrylic (or PR?). Very cool.

 

[Texatdurango]

George,

Do you use the black alumilite, or add pigment to the clear?

I use the clear and have been adding Alumilite black dye but just last night realized I had a big jar of carbon black PearlEx pigment so I cast a few blanks. I'll see how they turn and polish before commenting further on them.

 

[Robert111]

Another way of saying what Scott said - is that it is better to thread the outside first, put some kind of a support cap on it, and then thread the inside.

Different PR has different characteristics so the technique and sequence of threading become VERY important.

I have not done this, only reading the different posts on this as I intend to start doing the kit-less in the near future. (I hope I got it correct.) There was another thread on this very subject just a few days ago.

+1
I too find threading then supporting the cap threads on the barrel FIRST works best.