Is there a secret?

[egnald]

Hello all, A day or so ago my wife and I were going through my finished pens to pick some out to give as gifts when she picked up a nice Cigar made from Black and White Ebony and finished wiht CA. She announced "It's too bad it has that big crack in it". Wow, somehow the Grand Canyon of cracks had developed on the upper blank. I guess it didn't really surprize me because some woods like the Ebonys are prone to cracking. But what did suprize me I guess was that it just cracked on it's own, sitting in a tray in a pen box - no big temperature or humidity swings or anything. It is, of course, one of my favorite blanks as one of the black areas looks just like the neck and head of some kind of bird (to me anyway). I will most likely sand it down, re-finish it, and re-position the clip to cover any of the filled in crack that is still visible.

Ok, so does anyone have a secret for helping prevent this kind of thing from happening? I've read that some of the friction polishes help prevent micro-cracks from developing into full blown cracks. Does anyone have any experience along these lines?

Regards,
Dave

PS This is a picture before the crack appeared.

 

[jrista]

I have had some pens crack after I thought they were done. Mostly Tritons, which I think are prone to this as the parts, IMO, are just slightly too large for the tubes, and put undue outward pressure on an assembled pen. I've had wood and resins crack.

I have had some other pens crack as well. Sometimes days or near a week after assembly, after looking perfect until suddenly, there is a crack. I think it is material dependent, but I think its the same issue: pressure from compression-fit parts. The most recent cases were buffalo horn. I think that material is more elastic, so cracks take longer to appear (days, usually). I am quite careful when assembling now, and will even thin out tubes and grind down the fittings of parts, to make sure that there isn't too much compression, but sometimes I think some pens are just designed "too tight". With the buffalo horn, I think the elasticity of the material is why it doesn't crack until a few days later. I am in fact going to be re-making the lower part of an ultra cigar that cracked like this, and I'll be working hard to make sure that the parts are basically slip fit, and I'll glue them into place with loctite. I can report back once I get this done, and let it sit for a while, and see if for some reason the horn STILL cracks or not. If not, then I think my suspicions will be even stronger that these unexpected cracks occur as a result of too-tight of a compression fit.

Wood and resins will usually crack sooner. Resins pretty much immediately, the harder the more likely. Wood however, sometimes might take a couple of hours. I've assembled Tritons that looked perfect after initial assembly. Few hours later, though, I would suddenly see cracks I'm 100% certain were not there originally. As a matter of course now, I thin out tubes and file down the fittings of the kit to make sure that this no longer happens, and I glue the parts in.

I honestly have no other explanation for the unexpected random cracking I've experienced.

 

[jttheclockman]

No on friction polish. That is a myth. I believe the theory is oils can help prevent this such as tung oils and things of that nature. But you need to keep applying ever so often. Wood will continue to move and the more the humidity changes the more it will move. You will get answers like it never happened to me or it happened once or things like this. The truth is no one can tell you what a piece of wood will do. Remember to try to use dry materials. Many people get around cracking by stabilizing the blank before use. One method if not stabilizing is to relieve the pressure from the press in fittings and make them slip fit by filing the inside of the tubes. You are turning these blanks on the ends down to a small diameter that has very little material left. If there are micro cracks within the blank that are unnoticable then they can grow later down the road. It is not only ebony but many other species of wood can have this happen. I like to coat the inside of the blank with thin CA before gluing blank to tube and I always use epoxy glues because they have some give and do not harden. Some woods just have internal stress built into them because of growing factors. Sometimes where a wood is harvested can be a factor. Sometimes the time of the year it was harvested can play a role. Just no solid reason and answer to prevent. Good luck.

 

[magpens]

I see the bird neck and head on the lower blank.

But I don't see the Grand Canyon on the upper ! . . . I'll have another look in the morning.

 

[RichAldrich]

My 2 cents.
Ebony does not like getting hot. To me it cracks if it got to hot. Drilling, sanding and turning. Take your time. On and off let cool.

 

[KenB259]

I only make segmented pens and honestly I have never had a pen crack. Wondering if that comes in to play, perhaps smaller pieces of wood means smaller movement. All my wood is kiln dried and kept in a somewhat controlled environment, I run a dehumidifier in my basement in the Sumer and the humidity is around 45%.

 

[monophoto]

I have had items (pens and other stuff) as a result of changes in environmental humidity. As wood dries, it shrinks. If the wood is attached to something that can't move (such as a brass tube), it will crack as it shrinks.

It's winter, and the humidity is naturally lower. Wife has always insisted that we must have a humidifier on our furnace to maintain humidity in the house - something her doctor insisted on when she was a child. It does make a difference.

 

[MRDucks2]

I have a gabon ebony body on a Knurl GT kit that cracked after a year or so. It is one of my EDC pens now a some days you have to really look hard to see the crack, others it is Wide enough to easily see the brass tube on. All depending on temperature/ temperature change of where I am at.

 

[PatrickR]

i dont think there is any secret. Some woods are just more likely to develop cracks over time. There are things you can do to lessen the chances (most already mentioned). If I were selling pens I would avoid these woods totally.
the best lessons can be learned from luthiers that make hollow body acoustic instruments. They use similar woods, cut very thin, often cross-grain glued and then put under tension. Probably the worst possible combination. They go to great lengths to reduce the possibility of cracking. the people who buy the instruments also take precautions to lessen the chances of cracking (humidified/dehumidified storage etc). Pen buyers are not going to do these things.
I like these woods and use them for my pens. Some have cracked and some have not. I just live with it.

 

[jrista]

I like to coat the inside of the blank with thin CA before gluing blank to tube and I always use epoxy glues because they have some give and do not harden. Some woods just have internal stress built into them because of growing factors.

If you seal the inside with CA, does the CA soak through the wood? I generally finish with Pens Plus and Walnut Oil. Wondering if I tried to seal the inside of the tube with CA, if that would allow CA to leak through to the outside once the blank was turned down...

 

[jrista]

View attachment 328267

SO! I see a Shoebill Stork head myself! Is that what everyone else sees?

 

[jttheclockman]

If you seal the inside with CA, does the CA soak through the wood? I generally finish with Pens Plus and Walnut Oil. Wondering if I tried to seal the inside of the tube with CA, if that would allow CA to leak through to the outside once the blank was turned down...

How deep it penetrates is unknown. But remember we are only talking such a thin piece of wood when all turned down. One of those belt and suspender type deals. Any ounce of protection to try to ward off problems is worth the effort. I have never had a gabon ebony blank split on me and everyone knows I use lots of it.

 

[PatrickR]

I'll add this here as its the most recent "crack" post.
in 2017 I made three pentel bodies, African Blackwood, Brazilian Rosewood and Timborana.
These have lived indoors, stored in the same pouch. This year I noticed two cracks in the Blackwood. The other two are solid.
the two cracks are at 90* and at the thinnest area of the turning.

The diameter from crack to crack measures .347, measurement at 90* .326.
the other two are still close to round
a tube is often blamed, and may contribute to cracks but is not the sole reason.
in this case it would seem to be wood type and time. This pencil was fine for 3 plus years.