Rhinoplastic Problem

[reddwil]

Posted several weeks back about the problems I was having with the "chippyness" in turning rhinoplastic blanks. Well I'm Proud to say that with help from some members on here, that problem is gone. We'll call it a learning curve. Now I have a new problem. Last weekend I turned and made two pens, one Jr Gent and one Triton. Both turned and finished perfect. Assembly went fine. I took them in the house and placed in my display case. The next day I got them out to show my son. Both pens were cracked on both the upper and lower sections of the pen. I know for a fact they were not there after assembly. They were not dropped or touched after they were put away. My first guess was that it could possibly be a heat issue, around 50 in the shop and 70 in the house. my second guess is a assembly issue. However, on the cap of the gent, I had to add a little CA because of the loose fit, but both ends of that cap split. Any ideas????

 

[Russianwolf]

pictures help....

The display case.... is it in the sun? It may be 70 in the house, but the inside of a glass case can be quite a bit warmer in the sun.

 

[reddwil]

Mike I tried to make pictures but the cracks are hair line and with the color contrast in the blanks, you can't make them out in the picture. I will try again. No the display case is on a dresser in my bedroom. Stays pretty dark in there.

 

[Drstrangefart]

Ummmm.... Seems like an odd problem, but the first likely culprit is the temperature shift from shop to house. Or maybe it tried to expand/contract overnight from all the handling it just went through and couldn't so it split.

 

[jttheclockman]

What is that material made of??? Not familar with it. May have needed to aclimate to the air being you spun away most of it. Wood will do this too. You then added pressure when fitting the parts.

 

[maxwell_smart007]

What is that material made of??? Not familar with it. May have needed to aclimate to the air being you spun away most of it. Wood will do this too. You then added pressure when fitting the parts.

Being that it's rhinoplastic, I'm guessing cartilidge! :biggrin:

 

[DozerMite]

Where do you store your blanks? If it's in the shop, keep them inside until you turn them.
The temp. difference can cause cracking and even the heat from drilling will cause fractures that can show up later when the material expands from going inside to the warmth.
Just my opinion.

 

[Brooks803]

What is that material made of??? Not familar with it. May have needed to aclimate to the air being you spun away most of it. Wood will do this too. You then added pressure when fitting the parts.

I know the guy who makes these and last time I spoke with him he was using silmar 41 and combinations of mica powder and dyes (mixol I believe ) for the blanks. I do not know the amount of catalyst or what conditions they are cast in though. Some culprits could be, temp (already spoken of), pressing in parts. I know you had a slip fit but interal air pressure can cause a break at weak spots. When I assemble a cap I always do the threads first and then the end finial so there isn't a way to trap air when pressing either part in. Another possibility is if you used an end mill to square the blank. If they get dull they won't cut easily and create alot of heat which can cause splits that wont show until later.

 

[GregHight]

As with all synthetics, make sure you cut your blank long so that you can trim the bottom after drilling. Sometimes the crack can start from when the drill bit comes out of the bottom and you may not see it until later.

Due to all the alligator jawbone that I work with, I only use carbide tipped bits which I have found work much better on acrylics as they cut faster with less heat. Otherwise, I keep a spray bottle of water on hand to keep the hole cool while drilling any acrylics.

Good luck and let us know what you figured out!

 

[tgraffte]

RhinoPastic

I have found RhinoPlastic to be the best acrylic I have used. It drills very well, does not clog the bit, nor does it start to melt. When I turn the blanks, I use a chisel with a replaceable tip. Turn RhinoPlastic at high speed and use a very sharp chisel. I must also state that RhinoPlastic is made by my oldest son in Columbia, SC. Having stated that fact, I still have found his invention to be the best I have used.

 

[76winger]

Usually when I've gotten hairline cracks like that, I can trace it back to something that was slightly misaligned when I assembled the pen, thus causing the very thin material on the end to split. Then once the part is fully pressed in, the material goes back together to where it's almost unnoticeable.

 

[dankc908]

Just another thought with Rhinoplastic -- When I begin the process I turn the blank "to round" using either a 5/8" or 3/4" (depending on the kit) tenon cutter in my lathe (kinda like lathe drilling) and this seems to avoid some problems.

PS - I use a "4 flute" cutter that creates less heat and gives even pressure when cutting the blank.