Epoxy 101

[cyclone]

Hi all. I'm looking to do a fixer-upper job on a cracked plastic riflestock, and I've narrowed down my choices for filling-in the the cracks. They are, in what I assume to be a particular order:

1) resourcinal expoxy resin,

2) Oatey cement/similar variety, or

3) a strong "crazy" glue.

Now, I'm looking for [just] three key things (a) the fix-it job shouldn't look horrid (not too much excess goop hanging off the rifle) (b) the job should be as waterproof/watertight as possible, and (c) it should be a more-or-less long-term fix.

This would probably rule out my current weapon of choice, "gorilla glue" (an expanding "crazy" glue), because it's neither neat nor watertight, and because it can tend to flake off.

Another concern of mine is that this would be my first epoxy job, but it had to happen some time, so I figured no time like the present. From what I'm told, resourcinal expoy is waterproof. If that is the best choice, I'd welcome recommended brand names and idiot-proof expoxying instructions...

If the solution is an Oatey cement or something of that sort, I'd appreciate similar information - brand names, cement variety (e.g. PVC, CPVC or ABS)and tips on technique.

Thanks all.

 

[gbmarsh]

Hi all. I'm looking to do a fixer-upper job on a cracked plastic riflestock, and I've narrowed down my choices for filling-in the the cracks. They are, in what I assume to be a particular order:

1) resourcinal expoxy resin,

Well, first off. epoxies generally don't bond well to plastics without a 'mechanical' bond meaning you need to rough up the bonding surfaces quite a bit.
second epoxies really are a ##### to sand in their cured state.
The best solution for most thermoformed plastics is to heat weld them using a filler rod of the same material as the original part.

I also don't think you would have much better luck using the other adhesives that you listed. You would probably save a lot of time, money and frustration by just replacing the stock

my .02

 

[woodchopper]

I would have to wonder how the stock got cracked and if you should perhaps look at reinforcing the interior before you look at the cosmetic fix

 

[buckbrush]

brownells acraglass gel

 

[kodiak1]

Replace it don't cheap out. You fix it and are out on a hunt in a year or two or three and it breaks again on you in the same place and you will be muttering those emortal words *@$%^ I shouldn't have be so damn cheap.
Ken.

 

[Wrong Way]

The only sure way to fix a cracked synthetic with epoxy is as follows:

1. remove buttplate
2. mix 1/2 gallon resin with 1/2 gallon hardener
3. pour into stock until stock is completely full
4. reinstall butplate
5. Allow to cure then get friend to help you carry it out to the range.

 

[eltorro]

The only sure way to fix a cracked synthetic with epoxy is as follows:

1. remove buttplate
2. mix 1/2 gallon resin with 1/2 gallon hardener
3. pour into stock until stock is completely full
4. reinstall butplate
5. Allow to cure then get friend to help you carry it out to the range.

I did the Foam filling thinghy on a 10/22 plastic stock, so I lessen the sound it made when accidentally hit. I filled it nicely..... About one year after, I drilled the stock to install a swivel stud..... Believe it or not, the foam was still liquid.
I realize that the Epoxy will harden if mixed, but I thought it was funny...... I had to throw the stock away.

 

[cyclone]

buckbrush, any advice on the use of the gel?

Btw, this is not a cheap-out issue; the rifle I'm working on is notoriously difficult to dissassemble and re-assemble...

 

[tiriaq]

If it is notoriously difficult to dissassemble and re-assemble, would it be a Remington Nylon 66?
If it is, I recall reading of solvent welding the nylon. IIRC, carbolic acid was used. A call to the Remington customer service department might be in order.

 

[bluedcanoed]

Just a note of caution!

If you ever mixed up a gallon of epoxy resin with the proper amount of catalyst and poured it into a confined space the resulting exothermic reaction will generate enough heat to probably melt the container and very likely start a fire.

Cheers,

Bob

 

[Andy]

You didn't say what the stock was for - can you?

I repaired a black synthetic (plastic?) stock that had a cut-out for a receiver sight I wanted filled. I installed a few pins to give the epoxy something to bond to, built a dam around it and filled it with epoxy coloured with black earth powder from Valley Tools. After drying, I sanded to final shape and then I painted the whole stock with truck bedliner. The repair cannot be detected and remains solid.

As for your situation, if it's just a crack to fill (the repair has been done and it's cosmetic), colour some epoxy and fill, and then wet sand to final shape. Test the epoxy on a spot on the stock that won't show to make sure the two are compatible.

 

[Wrong Way]

triaq nailed it. If it is a Nylon 66, solvent welding is the way to go....I believe that it's either methyline dichloride or methyl-ethyl quitone peroxide.

 

[cyclone]

Wrong_Way, your application to be a prophet is in the mail!

tiriaq, you were dead right. Andy, it is a Nylon 66, and I just finished brushing down all the cracked inter-fitting with the Oatey ABS compound (which contains methyl-ethyl quitone peroxide, according to my science-minded brother).

Thanks all for your interest and advice.

Update: the ABS cement did the trick. I used an artisan's narrow paintbrush to apply the compound, as the regular applicator was just too bulky and messy. By the way, for those of you who've lost the bolt-handle, the fitting-hole is roughly 1/4 of an inch, so sanding down a 1/2-inch wooden dowel will get you a crude but effective replacement. This is definitely going to be a truck-gun; not pretty, just workable. Perhaps spray-painting is in order....