Stuff moves

Mark Knapp

Mark Knapp

Joined
Dec 20, 2009
Messages
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Here's a subject that is mysterious to many people. Why do materials move? Many natural handle materials move, some more than others. No matter what you do, cure it, dry it, stablize it, pin it, substrate it, glue it, captivate it, and seal it and it will still move. We as knife makers go to great lengths to keep expansion and shrinkage to a minimum but with some materials in some climates they will still move. It has been a recurring subject on this and other forums, in some cases (not so much here) it is with quite a bit of venom toward the knife maker or material dealer.

Movement occers, for the most part, due to a change in moisure content in the material, and to a lesser degree a change in temperature and I am pretty sure, though I have no proof, a change in barometric pressure. Fine furniture makers have known this for a long time. The effects can be mitigated in most cases by the methods mentioned above, but some materials were just not meant to be used on knives in some areas. You can do everything right and some materials will still move in some areas.

The average indoor humidity in Fairbanks in the winter is about 8%, so if I send a piece of handle material that has been cured properly to a maker with a humidity around 30% the material will need several months to acclimate to the new climate before it is used. To further complicate matters, if the knife is made and sent to an area with a different climate it will move again, and if it is an area with huge fluctuations in indoor humidity the material will continue to move forever with the seasons. A knife could have no apparent problems for many years and then all of a sudden shrink, expand or crack, especially if, but not necessarily if, moved to another climate.

As I mentioned, some materials are worse than others, horn (maybe musk ox horn especially) and ivory seems to have the most problems. I have spent a lot of time trying to figure out solutions to these problems, I have learned a lot but, still don't have all the answers. I have knives with exotic materials and technical assemblies all over the world and have had just a few problems. I am sure that I will be repairing knives every once in a while for as long as I continue to use exotic materials, I think it is worth it. I am willing to help other makers if I can.

There are lots of fine knife makers and material dealers, the thing to keep in mind is if something goes wrong with a natural material, it doesn't necessarily mean someone did something wrong. Pick an experienced maker, follow his instructions for care, let him know if a problem crops up and he will do what he can to fix it, no sweat. If the thought of something happening to your knife bothers you too much, stay away from the exotics.

Hope I didn't come off as some kind of know-it-all, just one man's opinion. Thanks Mark
 
Thanks for sharing your knowledge/experiences with us Mark.

The shifting of handle materials is kind of a "fact of life" in the custom knife world.
 
Mark, I'd like your opinion on pinning or not pinning Ivory. I have one pinned Ivory piece that is about 32 years old that has cracked at and into one of the pins on each side. Very minor, hair line cracks. I have another about the same age with no pins, or at least not visible pins and it has no cracks and not much if any visible or felt shrinkage.

I'm wondering if the handles were made without pins if that might reduce the incidence of cracking. My thought here is that as the ivory moves, if it did not have a pin to push against, it might not crack. It does seems that most of the cracks I see in natural handle material have a pin involved with the crack running away from or to the pin.

Paul
 
buy local?
 
sheathmaker said:
Mark, I'd like your opinion on pinning or not pinning Ivory. I have one pinned Ivory piece that is about 32 years old that has cracked at and into one of the pins on each side. Very minor, hair line cracks. I have another about the same age with no pins, or at least not visible pins and it has no cracks and not much if any visible or felt shrinkage.

I'm wondering if the handles were made without pins if that might reduce the incidence of cracking. My thought here is that as the ivory moves, if it did not have a pin to push against, it might not crack. It does seems that most of the cracks I see in natural handle material have a pin involved with the crack running away from or to the pin.

Paul
Click to expand...

Mark, I would like to hear your opinion on this as well. I have also noticed a much greater frequency in cracks around pins, and have almost eliminated the use of them in my knife handles. I have however, also had heartbreaking and severe cracking on ivory that had no pins. I am pretty certain that this was due to humidity changes. (the moisture controlled gun safe) I usually don't mind small surface cracks, and even like the way they give the ivory an aged look, it's the ones that go all the way to the tang and expose the knife to the elements that kill me.

Does anyone have any good advice on a technique for pinning ivory if it can't be avoided? I would like to know anything I can about working with the stuff.

Adam-
 
Kind of like our bodys shifting/changing as we get older. I hate when that happens. :D
 
Great post Mark. Educating and inquisitive at the very same time.

Thinking out loud: Pinning with a loose fit and filling in with a flexible filler. An intentional expansion joint allowing minor movement. I'm sure it's been done?

Subscribed.

Coop
 
Thanks for the post, Mark :thumbup:

Four or five years ago I bought a khukuri with a crack horn handle (i.e. from Reno, NV). When I received it (i.e. in Malaysia) the gap of the crack was narrowing down (i.e. from what appeared in the picture). After some times what is left on the handle is just a hairline crack mark. It seems something .. might be the weather or the temperature or the humidity .. I don't know .. caused a sort of reversal movement to the horn material.

Any explanation?

Mohd.
 
Great thread, Mark. This is the main reason that I don't use horn of any type anymore (that and the smell when grinding it). I do however use a good bit of ivory as well as wood which is just as effected. Here in the Ozarks the humidity is very high and air dried wood is usually 14% or higher in moisture. You can see where I'm going. This is why I use a lot of the oily exotics and stabilized blocks or woods that are more naturally stable..

Gary
 
Lorien said:
buy local?
Click to expand...

Actually Lorien, I think everyone should buy from a Fairbanks maker. :D:D.
Kidding aside, I would say that most handle materials are safe to be moved around. The safest thing to do with some of the most temperamental exotics would be to have the material cure and the knife made in a climate similar to yours or locally. But what's the fun in that, the most rewarding part of knife making for me is using exotic materials and sending them to exotic places, I can only guess that it would be the same for collectors. I say take the risks, but do the homework, and maybe bear a little of the responsibility if something happens down the line.
 
well, maybe a less risky way to handle handles would be to buy supplies from a supplier who is proximal or lives/works in a place with a similar environment.
Or to use handle material which comes naturally from the place where the knife is made.
Or if one is a customer, to supply material which has been stored in their place for awhile.

So, who's responsible? It's true that natural materials will morph in shape somewhat over time, however, when a maker does not perform due diligence and supplies a knife to a customer which exhibits substantial material shiftage, it would be a cop out in my book if said maker shrugs his shoulders and says; 'Well, shift happens'. If said maker takes on material that a customer sends in order to make a knife, but is held to a rigid timeline, is that the customer's responsibility?

Aftermarket knives, second hand knives I don't think should ever be held to the same standard as when the knife is purchased directly from the maker, in that the materials chosen at the time of the order might reflect some thought upon the environment where the knife is made to end up in originally.

Ah, too many variables, and not enough coffee.
Great topic:thumbup:
 
sheathmaker said:
Mark, I'd like your opinion on pinning or not pinning Ivory. I have one pinned Ivory piece that is about 32 years old that has cracked at and into one of the pins on each side. Very minor, hair line cracks. I have another about the same age with no pins, or at least not visible pins and it has no cracks and not much if any visible or felt shrinkage.

I'm wondering if the handles were made without pins if that might reduce the incidence of cracking. My thought here is that as the ivory moves, if it did not have a pin to push against, it might not crack. It does seems that most of the cracks I see in natural handle material have a pin involved with the crack running away from or to the pin.

Paul
Click to expand...

Hi Paul, I think you are right, pins are an invitation to crack, of course there are remedies that help reduce the chance of cracking, and some ivories are worse than others. I think that elephant is the worst no matter how old it is, then mammoth, then ancient walrus.

Some known methods to reduce the chance of cracking at pins are;

Make the holes in the scales a little oversized.
Do not try to flare pins into ivory, countersink it first, but still....
Drill one hole in the tang just a little oversized for location, usually the closest one to the guard, drill the rest of them well oversized to allow the handle material to move without cracking at the pin.

For sure any design without pins or fewer pins will have less chance of cracking.

I think that is a mistake to completely fill a hidden tang knife with an ivory or horn handle with epoxy because the tubular shape of the material has no room to shrink. I try to bond the tang completely on both ends but leave a small air space along the tang for room to shrink.
 
stabber said:
I heard soaking the handle in mineral oil periodically would help.
Click to expand...

That is an accepted practice for many, but all of the ivory people that I talk to not related to knives say to never put any oil on ivory. I don't, any one else have experience with this?
 
DesRosiers said:
Mark, I would like to hear your opinion on this as well. I have also noticed a much greater frequency in cracks around pins, and have almost eliminated the use of them in my knife handles. I have however, also had heartbreaking and severe cracking on ivory that had no pins. I am pretty certain that this was due to humidity changes. (the moisture controlled gun safe) I usually don't mind small surface cracks, and even like the way they give the ivory an aged look, it's the ones that go all the way to the tang and expose the knife to the elements that kill me.

Does anyone have any good advice on a technique for pinning ivory if it can't be avoided? I would like to know anything I can about working with the stuff.

Adam-
Click to expand...

I hope what I wrote in the above post helps.
 
SharpByCoop said:
Great post Mark. Educating and inquisitive at the very same time.

Thinking out loud: Pinning with a loose fit and filling in with a flexible filler. An intentional expansion joint allowing minor movement. I'm sure it's been done?

Subscribed.

Coop
Click to expand...

Yep, I use that concept a lot. Anybody else?
 
mohd said:
Thanks for the post, Mark :thumbup:

Four or five years ago I bought a khukuri with a crack horn handle (i.e. from Reno, NV). When I received it (i.e. in Malaysia) the gap of the crack was narrowing down (i.e. from what appeared in the picture). After some times what is left on the handle is just a hairline crack mark. It seems something .. might be the weather or the temperature or the humidity .. I don't know .. caused a sort of reversal movement to the horn material.

Any explanation?

Mohd.
Click to expand...

That happens quite a bit, sometimes from summer to winter and back again. It is because the material absorbs moisture from the air when the air is moist and then dries when the air is drier. It changes with the humidity.
 
Great thread topic and lots of good information. I've also heard of making holes for pins oversized and not peening tightly to allow expansion/contraction.

Maintaining consistent humidity is a good way to prevent issues but can be easier(and cheaper) said than done!

Also, instead of epoxy or cyanoacrylic type glues, something that does not completely harden, such as Barge contact cement, is something that has worked great for me on materials such as leather and stag. For many years it was the norm for shoemakers. It dries very much like rubber and pliable.

Peter
 
Lorien said:
well, maybe a less risky way to handle handles would be to buy supplies from a supplier who is proximal or lives/works in a place with a similar environment.
Or to use handle material which comes naturally from the place where the knife is made.
Or if one is a customer, to supply material which has been stored in their place for awhile.

So, who's responsible? It's true that natural materials will morph in shape somewhat over time, however, when a maker does not perform due diligence and supplies a knife to a customer which exhibits substantial material shiftage, it would be a cop out in my book if said maker shrugs his shoulders and says; 'Well, shift happens'. If said maker takes on material that a customer sends in order to make a knife, but is held to a rigid timeline, is that the customer's responsibility?

Aftermarket knives, second hand knives I don't think should ever be held to the same standard as when the knife is purchased directly from the maker, in that the materials chosen at the time of the order might reflect some thought upon the environment where the knife is made to end up in originally.

Ah, too many variables, and not enough coffee.
Great topic:thumbup:
Click to expand...

In my original post I suggested; Pick an experienced maker, problems will be mitigated and few. Do your homework to see if certain materials were meant to live where you live. Cure the material for a while after it is recieved by the maker. Take care of the knife after it is recieved. After that if a problem arrises the maker should fix it, I want my knives to look good forever. But in the long run the buyer of the knife made all of the choices, he should understand that he bears the responsibility that the knife ended up where it was and was taken care of in the way that it was. I'm not saying he is out of luck, I'm just saying it's not always the makers fault, in dealing with a problem cut the guy a little slack.

I have a lifetime warrenty (under normal use) on the knives I make , that includes all we are talking about here. Most of the makers I know do the same, we don't want handle failures with our names on them out there.
 
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