Knife handle making - how much to force the wood

[Pierr]

Hi,

following on the thread "are stick tangs realy weaker?"

Xunil says:

You often see a similar effect where someone used a 6mm drill to then fit a 6mm pin (you wouldn’t believe how many makers don’t use a reamer or who force their assembly together using clamps or even a hammer) your pins are basically constantly trying to force the hole they are fitted in to be wider, unless it was properly prepared. This is a depressingly common area of scale material failure.

I have put handle on a few lauri blades (stick tang) and one Spyderco mule (full tang).

When preparing the handle for the stick tangs, so far I always made sure the hole was no larger than the tang and that it could only be forced in with some hammering. I still put epoxy of course but I go for a very very tight fit. It happened to me that I could not hammer down the handle all the way down and had to just destroy it an start all over again.

Similarly when doing the holes for the pins on the Mule's scales, I kept that just large enough -yeaw, with a drill and some files, don't have other tools) and had indeed to hammer down the pins. I thought this would give more robustness through the very tight fit.

Now Xunil's description would point out that I have it all wrong.

So what are the reactions here? Is a tight fit putting bad stress on the wood? Or is it a guarantee of the stick tang never going out?

 

[Chainsaw]

I'd go for more stress on the wood, wood and metal react to temperature and humidity by expanding or contracting.... at different rates, not good. my 2 cents

cheers,

alan

 

[Siberianfury]

a looer fit will be stronger, because their is room for the expxy to cling on.

peening the tang over is a great way to insure that blades not going anywhere

 

[Hugo]

I hear some people cut a few feather marks into the tang, that way when you do the final fit, with a bit of taping it can't be pulled out easily.

 

[Pierr]

I hear some people cut a few feather marks into the tang, that way when you do the final fit, with a bit of taping it can't be pulled out easily.

I do that and also put some file marks on the tang to give epoxy something to hold on.

 

[John Fenna]

I do that and also put some file marks on the tang to give epoxy something to hold on.

I tend to use a "Modified Henry Rabbet" construction with a tight fit and notched in the tang for both keying and a "barbed" fit. I also often make the tang into an eye and pin or rivet through this.
If using just a "push fit" then I do like these guys

 

[brancho]

When I make a knife I make sure the handle fits without force as this can end with gaps if not which happened on my first knife.

I recently took a handle of a knife and after boiling the wood for about an hour to soften the epoxy I stll ended ended up with the blade in a vice and my foot on the bench and I only just managed to loosen the handle to get it off. I usually put notches in the tang for the epoxy to hold onto.

 

[Xunil]

Traditional Scandi knives are often force fitted in the final assembly. There is a fine line between just enough and too much and only time will tell whether you get the balance right. Another significant factor is that many of the handle materials traditionally used on Scandi knives are softwoods.

Most of my knives are hidden tang, but most of them have the tang running at least two thirds and (more usually for me) three quarters of the length of the handle material. I usually fit a pin in the last third of the grip, somewhere near the end of the tang. By doing so I can make the whole assembly with tolerances that allow me to use gently hand pressure to fit the whole lot together. A little warmed epoxy on all surfaces slicks things up during final assembly and ensures that the epoxy is evenly distributed throughout the assembly.

Peening a tang on a through tang knife is a great way of securing it provided you take it only as far as it needs to go. I have seen folks go overboard on the peening resulting in a broken handle or, just as bad, a handle that is very difficult to remove but that has been made a loose fit during the peening process.

For full tang knives I ream out all holes so that the whole lot can be easily push fit assembled with gentle hand pressure. I never use clamps (it's far to easy to push too much glue out and end up with a dry joint) but I do use either plastic clips which are similar in principle to large clothes pegs or strips cut from an old inner tube wrapped around the setup to give a gentle, constant and evenly distributed pressure. I also use inner tube strips when glueing up longbow laminations for the same properties of gentle and even pressure.

As long as your surfaces are properly prepared you should need minimal pressure during the final fit.

On hidden tangs with no pin then the methods mentioned previously by others work well to introduce miniature barbs and similar raised areas on the tang which help the glue to key onto the tang and can also embed into the handle material itself.

Do this experiment:

Use a 6mm drill and drill through a scrap piece of steel or handle material.

Try and push fit a 6mm pin through the hole.

It won't fit in either of them without a lot of force and it might not go into the hole you drilled in the steel regardless of how much force you use.

Now try the same experiment but this time use a 1/4 inch drill (which is 6.4mm) and the same 6mm pin as before.

You should have slightly better results but they should still be tight enough to provide a good assembly and a strong glue-up but, depending on your handle material, you may still find it is on the tight side. Many natural handle materials will expand or push away from the pressure of the drill and recover slightly when the drill is removed, so while your drill may have gone through it is very rare to end up with a hole that equals the size of the drill you used.

Repeat the above experiments using a 3mm drill and 3mm pin material and then a 1/8 inch drill with the same 3mm pin material for almost identical results.

The forces used in assembling a knife should work to hold it together, not work from within to push things apart.

I was tempted to end that last sentence with the words "young Jedi"

A lot of knives are made without considering these issues and they end up holding together. A lot of them fail and leave the maker or owner automatically blaming materials. Sometimes it may be the materials but, often, it will be that they were all assembled 'pre-loaded' where there were pressures and stresses introduced on assembly which are constantly fighting 'outward' and running the risk of compromising the materials themselves.

My view is that you should build quality in and not build it out, and a few extra minutes spent in the manufacturing processes can pay off so why not ?

Another consideration is for makers who are increasing their volume or looking to go semi-pro or full time. Do you really want to run the risk of a knife returned due to failure that could have been prevented ?