Crack in a Cocobolo

[airrat]

I turned a beautiful Cocobolo pen earlier this week. Did the BLO/CA finish. Pen looked great. Today I have a hairline crack. I know the normal causes of this (something in brass or not straight when pressing, I took extra time making sure these would not happen) but I was wanting to know if maybe it was due to the heat produced by the BLO/CA .

This piece had alot of oil in it I assume due to it clogging up my sand paper.

Very depressing, it has a glitter effect in the grain and a gold/orange for the rest. posting from work so cannot post picture with this post.

Anyone have any answers?

 

[woodscavenger]

I had the same thing in several of my cocobolo pens. They all still look great but all but one of them from the same batch of wood have small cracks at the end. [!] I wish I knew. I let it sit for a couple of months and it seemed pretty dry. During sanding it didn't seem to get too hot. I wish I knew why....one of them was going to be my guild submission but now I am afraid to enter it with the hairline crack.

 

[DCBluesman]

First off, this is experience only. I've not done exhaustive research.

Extremely oily woods tend to have a lot of movement in them. Someone posted a link about wood movement that I can't find right now, but I remember agreeing with the author on that.

The movement is frequently caused by heat. The heat comes from a number of sources.

The first source is in drilling and tubing the blanks. While drilling and clearing your blanks, touch the unfluted area of the bit. If it's warm, the oils in the wood are being stirred up and movement is more likely. Slow down, cool the wood. Cool the bit. I think Wayne advises using the shop vac to improve airflow. That's probably a great idea.

The next source of movement is in the use of CA. When CA cures it releases heat. More CA equates to more heat equates to more potential for movement. This is not to say that CA cannot be used on oily woods, just that there can be an added element of risk.

A third source of heat comes from turning and sanding. The potential for problems increases here. Simply using a steel tool to remove wood from the blank causes additional heat. With that heat, we have the added problem of having halted natural movement if the tubes are glued in with CA.

With all of those sources of heat and movement, it should not be surprising that additional movement during cool down or during normal day to day heat and humidity changes can further stress a blank that is only a few millimeters thick. My best thoughts are to do all you can to keep heat build up to a minimum with these very oily woods. FYI, the only pen I have had crack after assembly was a BOW pen that I had CA glued the tubes in and finished with friction polish. I was surely courting disaster! []

Among my list of "very oily" woods are cocobolo, olive wood, ebony, brazilian rosewood and a few of the other "true" rosewoods.

Shane--based on experience, do not submit a repaired pen to the PMG. Your submission is expected to be technically flawless. I've recently submitted an article to Jeff that describes my experience and suggestions. [8D]

 

[timdaleiden]

Originally posted by DCBluesman
<br />

Extremely oily woods tend to have a lot of movement in them. Someone posted a link about wood movement that I can't find right now, but I remember agreeing with the author on that.

Here they are:

http://www.morlanwoodgifts.com/MM011.ASP?pageno=82

http://www.americanfurnituredsgn.com/wood_movement.htm

(Sorry again if my sig loads slowly...I am working on it)

 

[airrat]

Thanks DC, I have not thought of the drilling process. I will try something to cool down the bit during that part. I did use CA on the brass tubes as well. I seem to have a love hate relationship with epoxy. I would love to use it but I hate it when it never sets up.(measuring problems)

 

[timdaleiden]

Originally posted by woodscavenger
<br />one of them was going to be my guild submission but now I am afraid to enter it with the hairline crack.

I agree with Lou that a crack would work against your submission. I am glad that you are considering submitting your work to the Guild. You do have the talent to make it there, IMHO.

I have noticed that there have been some anti-guild feelings expressed on this forum. I am saddened that some people feel that way.

I find these sentiments bewildering. One of the two folks that got this site up-and-running is a member of the Guild. Most of the original members here are also members of the PMG. A number of tutorial articles that are here, or are frequently referenced, were written by Guild members.

I think that nobody should feel compelled to join the Guild either. There is nothing wrong with that.

One more thing I want to add is that Guild members are not tool snobs, we do not have secret meetings (unless the rest of them are keeping something from me), we do not all agree on everything, and we do not sleep with mini-lathes under our beds.[]