Antler pens developing cracks

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Chasper

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We make and sell quite a few antler pens, at least 150 of them in a year. Occasionally one of them develops a crack in the antler before it is sold, it has been a several years since anyone returned one that had developed a crack. So cracks are rare, except for one show. This one show is in the winter in a convention center, the pens start cracking on the second or third day of the show. The last time we were at this show we had 18 cracked pens. Most of these same pens had been in our inventory for a few months at least. They had been to other shows in all kinds of weather, they had been loaded up and hauled thousands of miles, some of them for as much as a year to dozens of shows with no cracks developing. Two days in this show and a third of the antler pens we had were cracked. I'm not planning to take any antler pens along the next time we go to this show.

Why are the cracks developing at this one show only. It is not terribly hot in the building. Humidity may be very low, I've never checked. This wasn't a one time occurrence, it has happened to a lesser extent 4-5 times, but only at this same show, same location and at the same time of the year.

The pens were made of several types of antler, whitetail deer, mule deer, elk, caribou, and moose. As far as I know all types cracked equally, the antler was well dried, but some was drier than others. I don't rule out that some types of antler or dryness of the antler could be the issue. Sometimes only one section of a two section pens cracked and the other section was fine, even though both sections were made from the same piece of antler. 18 pens developed cracks, but 35-40 more did not. Larger diameter pens developed more cracks than skinny pens.

What causes these cracks to develop? How do I keep them from cracking?
 
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osuataltus

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I do several antler pens during the year. I've found when I generate too much heat they will crack later. I stop three times when drilling and let the blank cool, take my time turning and let cool and then wet sand. Since doing this there has been no cracks.
 

ed4copies

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Obviously this is a guess!!!

Winter and convention center probably means very low humidity. Outdoor air comes inside and, without additional humidity added, static electricity is a big concern--low ambient humidity. A couple days sitting in this condition, under lights I am guessing (again) that warm the antler even further and cracking develops. Next year take a good temp-humidity guage (or 3-4 cheap ones and average the readings) and see what you are dealing with.

All stabs in the dark!! Hope it might help!

Ed
 

leehljp

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Gerry,
Cracks in different materials and conditions intrigue me and being a very curious person, I ask a million questions to myself :oops: about that subject. One area of "cracks" that I have heard (read) only one person on here mention is - using flexible glue or rubber epoxy/CA; and I will add that the question "if drilling the hole about 1/64 (or 1/32 if possible) larger than normal" would allow expansion space?

What we don't know is the exact cause. (In some cases we do - sun light, hot dashboard, humidity swings on green wood, etc) Many things have been mentioned. For your situation - just a thoughtful question: Is it expansion and contraction of the material, or is it the solid hold on the glue or the differences in expansion rates of brass tube vs material. IF it is from different expansion rates or inflexible glue hold, then expansion/contraction space AND flexible adhesive material are both needed.

BTW, for those of you that grew up using wooden handled hammers, the reason that the vast majority of hammer heads come loose is not the blows, but the humidity swings it goes through over the course of a year or two. Hammers that have a tight head on it can be hung on a wall in an unheated & unairconditioned shop, allowed to stay there for 18 months to 2 years without being used. After 2 years the head will be loose. Humidity expands the outer cells against the steel head; the outer layer of cells are crushed as the handle swells (microscopically) from high humidity; then as it drys, it contracts; repeat a wide swing in humidity and the second and third layers of cells are crushed; then humidity drops for a few weeks; Loose head without being used. - a summary of Bruce Hoadly's explanation in "Understanding Wood".

I learned from the school of pure embarrassing experience through the making of two nice tables (my first 2) 40+ years ago that Wood MOVES with humidity swings. Those two tables are still in use today with the cracks in them - from my trying to make boards that crossed each other NOT move - with the use of screws and glue. Nature won! o_O

Just to make it clear, this is not about wood per se, but the issue of two different materials and different microscopic expansion rates in extreme situations - and which gives first.
 
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jttheclockman

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Well Not at all an expert of anything but not afraid to weigh in on things. Just like wood antler is a living thing and expands and contracts as such. You do not say if you glue the blank to the tube with epoxy or CA. I would think epoxy would give you a fighting chance as with wood. It can flex some. You do not say if you finish the outside of the material and if you do not then you leave it open to moisture and humidity changes. It can help to seal the inside of the antler before gluing in with epoxy, by CA . If you leave raw and with marrow it will absorb moisture so you may want to change that. Also when you talk convention center the humidity changes daily in those place because of the people. It can be dry but as the show builds up the humidity changes with everyone breathing air. Now if you can get people to stop breathing while they are there you will have a better chance of not cracking. Other shows may have a smaller crowd or the air conditioning system maybe different and draws humidity out or none is used. Just some guess work as others are too.
 

bsshog40

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I have only done a couple antler pens. I didn't even know that you finished these. I just buffed my out and left them natural. Haven't had any problems with cracking but they are only a few months old. Guess I'll need to keep an eye on them.
 

1080Wayne

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The initial three posts above in combination probably cover the most important factors . Heat during drilling may initiate microscopic cracks that don`t propagate through until it gets into the very low humidity environment . To check if that is a factor , drill some with water continuously in the hole to keep it cool enough that the drill bit is never too hot to hold in your hand . Compare them with some drilled your regular way in a low humidity environment . Maybe microwave oven would show a difference ? Similar testing could be done on adhesive systems .

I don`t make many , but when I do the I seal the inside with thin CA before using polyurethane glue to glue the tube in . I also seal any exposed marrow on the outside with CA . My climate dictates that the antler I use is always at 5-6 % moisture content , so quite different than your conditions .

To keep your current ones from cracking , perhaps display in a clear closed case with a wet sponge (hopefully not visible) to keep the humidity up . Most important thing though is to warn customers about what can happen to their pen in a dry environment .
 
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Lucky2

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Gerry, you failed to mention where the convention center was, knowing that could get you closer to the proper answer. Personally, I think it was one of these two things that caused the cracking. The cold weather, and the antlers acclaimating to the different conditions outside and in the center.Where do you live, and what was the weather like there compared to where the sale was? If one area is much different then the other, in weather and temp conditions and humidity. Then that probably is the culprit. There's a place in the states that dates and identifies woods of all types, I don't recall who it is. But there's a very good possibility, that it's a government operation. Good luck finding out, I'd like to know also.

Len
 

Dehn0045

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I started to type this prior to the other responses, just getting back now to finish it up and most of what I have to say has already been covered. I'll post it anyway, maybe you'll find it useful:

I HATE it when my pens crack, but being a low volume turner I don't have much of a sample size, but based on my limited experience I have a few suggestions:

1. Store blanks in a climate controlled space. Changes in relative humidity is towards the top of list of causes of cracking.
2. Use a urethane glue (like gorilla glue) for gluing tubes. I believe the sponginess of the glue allows for a little expansion/contraction without cracking
3. Soak the drilled holes with thin CA prior to gluing tubes to stabilize/seal the blank. You may need to re-drill or start with a slightly oversized hole.
4. Sand or ream the brass so the components are slip fit (or just less tight), use a small dab of blue loctite threadlock to secure the components.

I have heard about stabilizing antler (either professionally or using cactus juice), this might be worthwhile depending on circumstances.
 

penicillin

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The more details you provide, the better the responses. I would like to know more:

* Please post photos showing examples of the cracked antler pens.

* You don't want to say where, but can you make statements about the general climate of the area? What was it like? Was it consistent year-to-year?

* Would it help to learn more about the climate and conditions when the pens were made?

* Tell us more about how you make the antler pens. How do you drill? What speed? What glue do you use? What finish, if any?

* Do you do anything special, different, or unusual that might give us additional clues?
 

Chasper

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Great answers. To respond to some of the questions raised:
Show is in winter in northern US, outside temp always below freezing.​
Pens are made in Southern Indiana, more moderate in winter.​
Keep in mind that these same pens have been to Florida, Texas, New York, Ohio, Kansas, Minneapolis, and many places between over a year, they didn't develop cracks at any of those locations.​
Glued with non flex CA​
Drilled on lathe with entry/exit mark method, slow speed, about 400. No pre-rounding before drilling. Antler does heat up in drilling.​
Finished with CA, 6-8 coats​
I'm attaching a picture of one of the pens that cracked, this is the most common type crack, but I have seen them split from end to end with the antler totally separated from the tube, no glue holding it in place.cracked pen.jpg
 

Chasper

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One more set of factors that may be relevant. Conditions around travel and show set up.
Day one: Pens are loaded in van at home, van in unheated garage overnight, probably 45 degree temp. Pens are packed in hard sided cases.
Day two: Drive 6 hours to show, leave car overnight in urban parking garage, probably 10-20 degree temp.
Day three: Unload and set up booth, pens stay in heated convention center overnight, probably 65-70 degree temp
Day four: First day of show, no cracks on any pens
Day five: 5-6 hours into show, notice that one pen is cracked, find one more at end of second day of show
Day six: 8 more pens are cracked in morning of third day of show, additional 8 are cracked by end of third day
 

jttheclockman

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Has to be the extreme shifts in temps. We tell people not to do exactly what you are doing. Now would it help if the blank is not glued in with CA, who knows it may. Don't forget metal too expands and contracts as well. Not as much as woods and other materials but all happening and gluing to a solid surface to is asking for a problem and that is why I always use epoxy for gluing pen tubes. If the other shows that you do there is not as much temp shift could be the clue. Remember too if you press those fittings in there is pressure applied to those thin ends and maybe any small internal crack is just exposed now. I believe the temp shift is your problem You can get away with woods and acrylics and even metals but as we all know some woods are temp sensitive too like snake wood.
 

leehljp

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That is a stress crack. How to relieve the stress in future pens? Allow movement. I don't think you can control your environment totally and you do have a wide range of environments.

We know that the speed (quickness or slowness) at which newly shaped metals (by heat) are cooled or quenched dictates the crystalline structure and hardness it takes on. It might be that at certain temps, the quickness at which the pens are heated or cooled in changing environments could itself be the cause.
 

BRobbins629

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My theory is that there is stress on the blank due to pressing in fittings and is exacerbated with the temperature fluctuations. Best solution for crack prone materials is usually to ream out tube to get a slip fit and glue fittings in. An interesting test would be to bring some drilled, glued and turned blanks to your next show at this location but not assembled into a pen. Perhaps some drilled only blanks as well. What happens to these if anything will go a long was to better identify the problem.
 

1080Wayne

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Well there is a fairly simple cheap solution to your problem . Pack the antler pens into a couple zippered binders . Take them into the hotel room with you when you leave the van in the parking garage . Remember to put them back in the van when you go to the convention center , and make them the first items you take in .

Interesting though that you haven`t had a similar problem with some of the crack sensitive woods . I guess we all now know that antler is less forgiving . Thank you for giving me the opportunity to learn something today .
 

darrin1200

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One of the possible factors you haven’t mentioned, altitude. Is there a significant change in altitude from home to the convention center. Because air expands as the elevation increases, and since you have essentially sealed small air pockets (pores) into the blank, the expanding air could add additional stress to the blank. If this is the only show that occurs at higher elevation, then it could explain why it is the only place with this problem.

It’s been a long time since I was involved with scuba diving, so I don’t remember at what height affects occur. But think of what happens to your eardrums when driving up steep mountain hills.

Just a thought.
 
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