Some thoughts on kydex shaping and forming

[DerekH]

I have been toying with the idea of making my own kydex for awhile now. While I have experimented with a few different things, I have yet to really make one successfully, and I think it was due to a number of issues I hadn't considered and that I didn't see covered in any of the "How To" videos or threads I had seen thus far. With that in mind, I thought it might be a good idea to mention some of those issues, see how others deal with them, and maybe get some detailed information about kydex forming up for others looking to try their hand at it like I am doing.

First off, my setup up until this point has been about 8 old school neoprene mousepads, two 1" x 8" boards, and myself standing on them to shape kydex. Now one of the things I have heard a few times here and there is that the amount of pressure applied will determine the "crispness" of the end product, and while I kept it in mind, I never paid it as much attention as I should have. My method of standing on a board to apply force to the pliable kydex has as yet proven to be not very productive. It could be the pads, but ultimately I think it comes down to the amount of pressure that is being applied. At best, I am putting maybe 235 lbs of pressure down on the kydex while around the knife, and that is if I am holding perfectly still. Add to that a propensity to move and fidget a little, a lack of patience, and me trying to pull myself down using a countertop as leverage, and you get maybe around 270 lbs of actual force, and that isn't perfectly vertical or stable.

I think this plays directly into my next problem that I encountered; spacing of eyelets from the edge of the knife, both blade and spine side. One thing I noticed after I was done with my crude method of forming is that the kydex, while shaped to the knife, wasn't really that well shaped. It bowed in the middle. It fit it, and some of the more extreme features were really nicely forced into the kydex shape (the beginning of the handle scales, etc...) but it didn't look near as crisp as some of the others I have seen. So I looked at the kydex from the side. The fit of the kydex to the knife was good. Not great, but good. The bowing didn't help, but while it was shaped like the knife on the inside, it was faint. This could stem from me using the thickest possible kydex I could get my hands on (0.093" I think) or not getting the kydex hot enough (225° in the oven) but I couldn't help feeling that maybe if more pressure was applied in a steady manner, maybe it wouldn't have been such a problem.

Having some crudely formed kydex, I went on to drill a hole and put in a single eyelet. My goal was to still be able to get inside to clean out any shavings or anything from the drilling of the other holes, and it worked. So I went and drilled some holes. What I didn't take into consideration though was distance from the knife edge and spine. After drilling the holes, I found that if the knife was sheathed, and the eyelets were in place, the sheath was so tight I couldn't actually get the knife out. I talked to a buddy of mine that has been known to make a lot of kydex for ESEE knives, and he said he put his eyelets a minimum of .5" from the edge and spine of the knife in his sheaths. Mine was closer to .25".

And that is where I stopped. I looked at some other kydex sheaths I have for other knives, I looked at my stock BK2 sheath that is injection molded nylon, and I got to thinking that the pressure issue would ensure a closer fit. If I got more detail, that would mean the kydex was better formed to the knife, and would mean I could theoretically put the eyelets closer to the edge and spine with less issues. To rectify this, I ordered an arbor press yesterday, and I have a line on some heavy duty neoprene padding that is pretty dense. I figure if I can sandwich the padding between two pieces of some quarter inch thick steel, the pressure from the arbor press should be fairly well transmitted directly into the kydex, causing a better form, and hopefully meaning I can have more room to play with the eyelet positioning. It should also be able to manage the pressure more directly, and cause less slippage of the top piece of kydex in a pancake style sheath.

So, giant wall of text over, what are your thoughts on my theories? Does more force equal better forming, or am I pissing in the wind here? Padding will make a difference I think, as well as fine tuning just how hot I am getting the kydex, so those two aspects will be dealt with as well, but ultimately I am looking for some feedback on the pressure idea and how that will translate to forming a better sheath.

 

[sonil]

also get it as hot as you can without burning it and be fast from the oven to the press...if you feel it takes to long to adjust it throw it back in the oven
good luck

 

[blade man]

If it's bowing in the middle, it sounds like it might have too much pressure from above. Try not using the boards or Doing it on a flat surface. Before I made my good press, I stood on my foam and boards one, and I'm only 150. Good foam makes a big difference. Try a blue camping mat from Walmart. It's pretty decent for cheap stuff. The mouse pads may not have enough compression to make a good mold.

 

[Cobec]

I personally stand on my press to get a good amount of pressure. I think the issue with modeling is the mouse pads. I started out using a blue foam camping mat which yield decent results. I then picked up some foam from Knife Kits which helped produce even better results. Like sonil mentioned the hotter you can get the Kydex the better. Try to get it as hot as possible without it melting and try heating it at a lower temperature for a longer duration rather then an extremely high temp for a shorter period. As for the eyelet issue, for myself it was trial and error. I eventually determined exactly where to put the eyelets or how close I could to get the right amount of retention. Like all things it took a lot of practice to get to the level I am at now. The three factors for a good form are the temperature of the material, pressure and the foam. Standing on it creates excellent results provided the Kydex is heated to a sufficient temperature and you have proper foam.

 

[dericdesmond]

I found some stadium seat butt foam-pads at Meijer that work pretty well for smaller items, its consistency is not far off kydex foam. I sometimes use them when my kydex press w/ foam I bought from knifekits is in use. Like $5-6 a pop. I have a large patio seat I sit in, I lay one down, lay the hot kydex and knife down, put the other pad over it, and just sit on it for a while, I dont even really worry about it being completely level, the foam typically works that out if sitting halfway properly. Doesnt work as well as an actual press but it works. I think I set my oven (12 inch pizzas sized oven) around 250-300 degrees depending on if Im sitting there and watching it or not. Once the kydex starts curling I know its either done or close to done, Ill typically reach in to see if its really flacid, if it starts getting shiny, smokes, or smells real strong, it got a bit too hot.

ETA-if you get a press that works properly and the kydex to the ideal temp, Ive found 105 lbs of weight to be suffiecnt in forming a good mold. I never use over 135 and no issues at all. Just stack actual weights on it, round ones or multiples hex style dumbbells and stack em.

 

[jwaj]

The best press will distribute pressure equally. For knife sheaths you could just get some 3/4 plywood and glue on some iso mat (gi green sleeping pad). I have seen others use stadium seats and other foam as well. Basically the cheaper the foam, the fewer sheaths you will be able to mold with it. I've tried mouse pads but they didn't work well, as it didn't form around the object well.

Instead of standing on the press, use quick clamps, or C clamps.

I heat the kydex up to around 275 in a pizza oven, depending on kydex thickness it usually takes a couple minutes. You could also use an electric flat griddle. The kind you make pancakes on.

 

[DerekH]

Deciding that I had little patience, I decided to modify my temperatures and see what I could do with more heat. I was very pleasantly surprised, and got the most detail I have ever managed on Kydex to this point. For 0.093" kydex, 275° for a few minutes worked perfectly, so much so that on my Becker BK16 I could see the transition on the grind at the saber area. Truly amazing. I will post up pics once I track down the camera the missus ran off with.

 

[jwaj]

Glad to hear you got the results you wanted. I still fight the urge to remove the sheath before it's cooled all the way. I now set a timer and walk away from the press.

 

[DerekH]

I was going to wait until I finished before posting any pics, but here is a pic of it as it is now:

Still need to cut off the excess, put a couple holes at the tip end, and set all the eyelets and polish the edges, as well as shape the mouth of the sheath. Coming along nicely thus far. What a difference temperature made in the detail I was getting out of it.

 

[Phydeaux]

I run my little toaster oven at 300-350°F, I leave the Kydex in for a few minutes to get it good and floppy. The foam I use is 3/4" from the local hardware store, a little softer than the camping matts, I glued it to some 3/4" ply wood. The press I use is a 2 ton arbor press I salvaged from a place i used to work. To maintain pressure while the kydex cools, I jam a piece or coat hanger wire into the gears of the press to keep the ram down. Once it is blocked in place I can go and do something else while it cools.

Sometimes I use c clamps to hold the sheath together, where some of the rivets will be. Then you can see how the knife slips in and out, and change the placement if necessary.

It looks like you could also use a heat gun to adjust the Kydex by the finger groove.

I found that if the pressing didn't come out the way I liked, I just put it back in the oven and try again and again and again... sooner or usually later it comes out the way I want it.

Ric

 

[jwaj]

Derek that came out really nice. If you decide to do any adjusting with a heat gun one trick I picked up is to wrap a wet towel or sponge around the area you don't want to heat up. It works great when forming a thumb ramp at the mouth.

 

[DerekH]

Here are the results of my first attempt after I got the temperature settings adjusted.

I still need to do a little shaping of the mouth of the sheath. Other than that though, it works. Very happy with how it turned out.