[HKEsq]

Just curious - what materials does HK use for the receiver, buttstock assy, etc.? I understand it is a carbon fiber reinforced polymer of some sort. One of you gurus probably knows. Thanks.

 

[Paletiger13]

hey

I beleive it is Nylon 66. Thats what was mentioned before. Let me know if you find someone who can weld it.

 

[Chopstix Kid]

Any plastics welder should be able to using Nylon 66 welding rods and a hot-air welder that will heat it to 400 degrees. There are alternatives to the hot-air method but from what I have found by talking to various welders in my area, hot-air welding would be the way to go.... the person doing the welding just needs to make sure they use an appropriate tip as not to heat-up too much surface area. In the area I live in, there a DOZENS of companies that do plastics welding... just search the web for your area.

There are several good hot-air units you can buy for under $300 if you want to make the investment for future projects... just Google "plastic welders".

And of course the popular alternative... Devcon Plastic Welder II.

 

[Chopstix Kid]

LAB REPORT!

Looks like (with some practice) you'll be able to weld at home with a common soldering gun. I pulled out my trusty Weller 140 watt gun and slid on the flat "plate" tip.

I took two pieces of scrap Nylon 66 and some strips I sheered off with a blade. I placed the ends together and gently heated up each end, slightly melting into them to produce a tack weld (to hold them in place).

Then I laid a strip across the seam and melted it into the seam. I went about 1/2 of the way down into the thickness of the two pieces. Extra material kept rolling over the top which I carefully "folded" back into the seam as I went, melting the "folded" plastic back in. I did this down the length of the seam.

I went back over it a second time, this time only going about 1/4 of the way through, carefully feathering the edges and smoothing the top (as not to leave air pockets) to create a nice 1/4"-1/2" wide bead.

I flipped it over and did the same onthe other side.

After about 30 mins of cooling, took a Dremel and ground the beads smooth and finished it with some 120 grit sandpaper.

I tested by trying to snap it with some pliers... the pieces bent and cracked before the weld did!

Wish I would have tried this before I used Plastic Welder II for covering the "window" created by milling out the magwell on my SL8, but I think when I pickup Tbostic's Gen-3 block kit I'll defintely try welding it.

Sorry I don't have pics to share but when I do the receiver mod I'll be sure to snap and post some.

 

[HKEsq]

Thanks for your reply. Interestingly, I had thought, "well this feels like Nylon." I figured HK probably went with something a little more high tech.

 

[boomfab]

It's not just plain Nylon 66. It uses carbon fibers mixed in the polymer for strength.

 

[bigdog2003_99]

when i soldered it, it did work for a while but in the end cracked-i dont know if it was because of the differences of the material in the rear and the receiver (black to grey) if you have any luck definitely post it... my best luck was devcons plastic welder 2 though

 

[Chopstix Kid]

Boomfab is correct, it is indeed carbon fiber reinforced Nylon66. If you're doing a conversion, you'll probably have enough scrap for the welding.

Devcon Platic Welder II works well because it's a "reactive" adhesive in that it creates a "chemical" bond... almost a "fusing" behavior. Additionally, it's designed for tougher to bond materials such as Nylon 66.

In the end, I prefer a "welded" approach... it's just a matter of getting your weld deep enough with enough heat to not only melt the weld rod, but enough of the surrounding material to get a good weld. For anyone who has done welding with a mig-welder, you know very well that the weld goes deep and and is reasonably wide.

I just got done welding in the "window" cover and gave it a good "whack" with a mallet... good to go. I also let the bolt carrier freely slam a dozen times or so... all is good. Ultimately with the back end, time will tell as it will take more of a beating than the window cover. I'll keep you guys posted.

 

[AviatorDave]

Yep, carbon reinforced Nylon 66. You can either hot air weld it, or solvent weld it. Hot air would be to fill huge gaps, solvent welds for tight fitting seams. You can melt chips of nylon 66 into the solvent if you have small cracks to fill.

Or you can solvent weld it with aqueous phenol, solutions of resorcinol in alcohol, or solutions of calcium chloride in alcohol. Aqueous pheonol in 10 to 15% water is most commonly used to bond nylon to itself and has a bond strength approaching that of the nylon itself.

 

[Chopstix Kid]

Dave

Or you can solvent weld it with aqueous phenol, solutions of resorcinol in alcohol, or solutions of calcium chloride in alcohol. Aqueous pheonol in 10 to 15% water is most commonly used to bond nylon to itself and has a bond strength approaching that of the nylon itself.

I read somewhere that calcium chloride in alcohol would do the trick. Any idea of the mix ratio?