the best foam for kydex molding?

J

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Aug 23, 2003
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I tried my first kydex today, using foam rubber from an old gym mat, and two metal plates that I stood on. the results were....ok. But the molding is really loose. The rubber didn't press that closely to the plastic, and I got it soft enough with the heat gun.

I've read that some guys use closed cell foam, which I'm having difficulty finding. I've recently found some tutorials that mention the use of neoprene.

So what do you guys use? Neoprene? Closed Cell? What are the choices?
 
I used the foam from the blue mats they sell in the camping section at stores, and it molded plenty well for me. (Simple press setup, two boards with the foam, and I put my weight on it.) I had to work it a bit to make the blade able to come out with the proper force, it was such a close fit. Are you sure it was getting hot enough?
 
This is a good question. There must be a foam that will stand the high pressure I use. My forging press tends to ruin it. I go through allot of foam. I like a deep impression.
100_1430_edited.jpg
 
I have heard that something called "blow molding" or "blow mold" is what is recommended but I ended up going with the blue sleeping mat found at walmart as well.

I use a hydraulic press set up and cinch it down tight until it has cooled.

SDS
 
Following some tutorials here and other places- especially the advice given by Normark
I was able to get my first one work out fairly well.

You can search those threads out

In summary this has worked for me-

Masking taped 2 layers of thicknesses on the blade to allow clearance.

I used a toaster oven to do the first mould and a heat gun to fit the retention.

Blue sleeping bag foam from Wal-Mart – layered and glued together to get about 3- 4 inches of thickness per side.
Steel backing plates minimum 3/8 inch
I started with 3/4” plywood, but it flexed a lot and took me to the limit of my vise opening.


*** HEAVY PRESSURE ***
Now I admit to being way too close to 300 pounds, but some sort of mechanical advantage is a must to get tons of force.
You have to clamp it tight and keep it there until the kydex cools enough to lose its elasticity.
I think heavy pressure and enough heat will solve your problem.
I don’t know how standing on it became the recommended SOP, but I think it’s so easy to better that.

Skip the hinged waffle iron press – like you see in knife kits.com. It causes the material to slip sideways with the uneven pressure.

Others have used c clamps and hydraulic presses.

I tried the c clamps, but juggled and dropped them a lot. It was cool before i was done.

I found using the mechanics bench vise I already had worked pretty well. It applied tons of pressure very fast with no movement of the materials.
If I did more that way, I would mount a vise with the screw vertically.

Use a spray lube as a mould release, like “Pam” no-stick cooking spray.

Once I was done, the impression of the knife was imprinted in the foam. It can be reused with a different knife, or just kept aside for the next time you do the same knife.

The best foam???
I’m sure that there are better, but it would be a trade off of $ vs., durability.
High production methods use vacuum moulding around a standardized form.

Attached is the photo of the first one I did using this method - I was happy with the results.

Note the difference between Bruce's photo and mine.
I did a fold over at the top with a rod in the tip to allow a drainage hole for cleaning.
Bruce used two seperate layers. He achieved a much nicer finish along the blade spine using this method
 

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Bruce , that sheath looks like it would require a large force to remove the knife because of the way the sheath locks onto the guard .
 
P4190057.jpg


I use the kydex foam like fludunlimited and I made my own press that gives me about 600lb's of presure on the knife. as you can see I get a lot of detail in the sheath.
 
mete said:
Bruce , that sheath looks like it would require a large force to remove the knife because of the way the sheath locks onto the guard .
Click to expand...

You got that right. It cant be removed without the use of the thumb tab. Simply use the thumb and a slight twist of the handle and it comes out nicely. Snaps back in good too. This knife is carried upside down
 
fludunlimited said:
this is what i used
http://www.knifekits.com/vcom/product_info.php?cPath=41_57&products_id=278
they sell a press to but I never got one.
Click to expand...

Use the same foam from knifekits as well. Works bitchin. I just stand on top of the press, Which is basically two pieces of 1" thick plywood held together with two large hinges. If I can't stand there for the time, i just put a few cinder blocks on top and come back in 5-10 minutes. Depending on how hot you heat up the kydex will determine on how well it takes shape to the knife. If you don't heat it up evenly, doesn't matter how much pressure you put, only thing you'll do with all that pressure is smash the knife handle! LOL.
 
I am using a couple layers of the 3/4in thick foam floor matting Fred Meyer sells. It is the stuff with the dovetail pattern on the edges so you can set em out however you want. I think it was $17 for a set. Been using the same pieces for over a year now with good results :)
 
I got the kydex hot enough to be "floppy", like wet leather. But maybe it should have been heated a little more. I also realize that I need more pressure on it. Time to get some clamps..
 
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