Kydex Forming Questions

W

Wapiti

Joined
Sep 25, 1999
Messages
483
So I have been learning to work Kydex over the last several months. And am greatly enjoying it. It is very different than leather in most ways, but similar in other ways. I have been working with leather only for sheaths (off and on) since about 1995.

Here are my first few questions.

One thing I have found is that I don’t always get the best hot form around the blade, or at least what I expect.

So far I have set my 10x16” press up thus (from bottom to top):
¾” seasoned birch plywood
¾” foam pad
¾” foam pad
¾” foam pad
0.08 Kydex and knife
¾” foam pad
¾” foam pad
¾” foam pad
¾” seasoned birch plywood
¼” steel plate, 8x10”

This whole sandwich sits on the corner of one of my benches, where a 4x4 runs down to the ~8” thick cement slab.
On top of the steel plate I place a 4 ton piston jack, and on top of the piston jack I place another 4x4 running up to the ceiling directly under one of the 2x6 rafters.
I am not sure how much pressure I apply, but I basically jack until it looks good and squished (I stop just before the foam starts to squish out the side of the press).

But I just don’t feel that I am getting as nice a form as I have seen others get (through the definition in photos I have seen here and elsewhere).
It may be that the time to get everything set up after I take the Kydex out of the oven but before I apply pressure is allowing the Kydex to cool down too much.
I let my oven acclimate for 30 minutes and I heat at 2750F for 7 minutes.

Any thoughts on what I could try differently?

I am pretty sure a better press would help. I have designed a press, similar to a hydraulic shop press, but it might be a while until I get hat built.

Another question I had was do most of you folks use the same amount of foam under as over the Kydex?
I was thinking of trying to lay the Kydex directly on the lower plywood, that way the back part of the sheath would be flat, and the front part would be formed.
I am sure others have tried this and was curious what you thought of that method.

Last question.
I am using 0.08 Kydex and it works fine for most of the blades I have done, but I have some problems with it on larger blades (12” +, kukris, etc.). It just doesn’t seem to form evenly, or have the snap retention I like. Would you suggest going up to 0.09 for the larger blades.
Or a large press?

Also, I am very happy with this source for Chicago bolt posts:
http://www.chicagoscrews.com/
Many of you probably already know about it, but I was pretty happy that they sell only the posts and for about $5 for 100. I like to use my own screws so that works well for me, and I could find no other source that sells the posts alone.

One of these days I will take some photos of my setup and post them on my website.

Thanks for any thoughts you can share.
Brome
 
Brome,
Remove 4 layers of foam, and try again. This should help in giving you better definition of the blade in the sheath.
Make sure the kydex is real soft (hot) when you wrap it around the blade.

For larger blades you have to make sure that the whole sheath is covered, and pressure is spread evenly. Also make sure the kydex fits close to the spine along the entire length of the blade, if you do fold-over style.

Laying the botttom of the sheath on a flat surface will possibly form the upperlayer in a way that it'll may blunt your knife while drawing and sheathing, as the edge may touch along the kydex. To prevent that, make sure the 2 layers are always formed symetrical around the edge, so the edge can't touch the kydex, and thus blunt the knife.

I hope this helps a bit..
:thumbup: Thanks for the link btw. I needed that.

Good Luck!
Martin
 
Martin gave you some good answers. The amount of definition isn't that important - it's a matter of preference. Too much or too tight definition causes it's own set of problems. Function is first and foremost. Try for a good lock-up with a not too hard release. Work on form after you get function down. I use .093 for all fixed blades - works better for what I'm trying to accomplish.
 
Before I form my sheath,I draw the shape of the blade on a piece of matboard
then cut out and tape to the blade,that gives you more definition plus gives you space around the blade so it won't be so tight and scratch the blade.I actually bought a press from knifekits,and it works great,one thickness of foam top and bottom,you can fine tune with a heatgun...Regards Butch----I just use hand pressure
 
Thanks for the thoughts.

Martin:
So you saying go with only one layer of foam above and one layer below the Kydex and blade? For some reason I thought more would be better. I will give that a shot.

Good point about keeping the pressure even on both sides to insure that the knife edge doesn’t strike the Kydex.

Mike:
Well I am usually all about function. Guess I just forget sometimes. Thanks for the reminder.
I have found that after I do the full heat form, I like to use the heat gun to fine tune the retention and fit. Works well for me.
I think I will try some .093 and see how I like it.

Butch:
I like your matboard suggestion!
I was trying to think of a way to “thicken” the blade when forming, so there would be just a little more room between the blade’s sides and the Kydex. I currently use two layers of painters tape on each side, but that is not very thick, and tricky to put on evenly on a sharp blade.


Sounds like I might be overdoing it a bit with the foam and pressure. I have been known to overdue things…

Thanks again.
 
It's also quite possible you are taking too long in getting the Kydex pressed. From my experience you only have about 10/15 seconds max to get it pressed. any longer and the Kydex has cooled to the point that it won't give the definition you are looking for. For a faster clamp try a 10" woodworker's vice. About $30 at Harbor Freight. Good Luck!

Richard
 
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