I've got a CRKT crawford that I bought to carry as a neck knife.

 

The knife/sheath are similar to the image below, except instead of the lower fasteners being screws as in the image, they're rivets on mine:

 

Here's an image that shows the type of sheath I have:

 

 

Issue is that the sheath doesn't retain the knife securely enough for me to wear it around my neck with the point up/handle down.  If I moderately jar it (like say, do a couple of jumping jacks), it falls out of the sheath.

 

Is there anything I can do short of getting a new sheath made to get the sheath to retain the knife better? My first thought is to replace the bottom two rivets with pop-rivets to attempt to get the kydex to clamp tighter.

You can try to add a little more tension yourself. Get a hair dryer (or more preferably a heat gun), and heat up the sheath. After its moderately warm just squeeze the retention parts closed a bit. Cool, test and repeat as needed until it has the retention that you want.

 

In the top stock photo, it looks like your gonna want to add more tension to the bottom left corner. It looks like that's how its retaining the knife. 

Pop rivets won't accomplish it.  I agree with effd, use heat.

Same knife, same problem.  (Stainless version)  I called CRKT and they sent a replacement sheath.  Same problem.  Tried ABS solvent...popped right open.

So I just ordered 1/8" Chicago screws and will drill a hole in the lower left corner (the retention area as effd said) to hopefully tighten up.

I'll have extra screws when they come, so if it works and you're anywhere near Monmouth county, I'll gladly give you  set-

Thanks for the responses - I have a heat gun, so I'll try clamping and heating.  I don't know much about kydex, but I assume you can reform it indefinitely by heating/cooling?

 

4redz, keep me posted on how your screw addition works out.  If I can't meet up I'll definitely send a SASE package if you're willing to drop a screw into it and drop it back into the mail to me.

I'll keep you posted...just hoping the diameter of the Chicago screw will be small enough.  Let me know if you have any luck after trying the heat gun-I don't know how I could heat & tighten one side of the Kydex without the other opening up because it's already fastened together, if you know what I mean.

Chicago screws shipped.  Will attempt mod this weekend-

I think I've modded the sheath now to where it has stronger retention while still releasing the knife when wanted.  Instead of squeezing the sheath halves together I instead grabbed the lower left edge and gave it a slight twist while heating with a heat gun.  The twist on that corner seems to be enough to keep it from falilng out, but the halves will still split slightly to release the blade when it is pulled.

The screws that came in are too large to use on the sheath.  Thanks for the update!

Wheres Atech? hes the kydex guy

Oh hay.

So, the screws that you see in the first picture are for mounting whatever belt attachment they had on it for that picture. It's under the sheath so you can't see it. There are still rivets under those screws. Re-heating and clamping won't do anything because, it can only be as tight as the blade is thick. Adding a little twist at the corner is a good idea. I personally wouldn't do it, just for aesthetic reasons, but obviously it worked for you. What I do, on 95% of the stuff I make, is add a small point where the turn of a screw would loosen/tighten the retention. Everyone likes things differently so why should they all be the same retention?

 

This is my CRKT that is a minimalistic design for wearing horizontally on the belt.

That is a very nice looking sheath.

 

The crkt brand sheath is only riveted, so not adjustable and too loose to hold the knife. I tried chicago screws but they were too large. Heat and bending is probably the only way to salvage the original sheath.