an unusual problem

[sunnybob]

My neighbour came round today. i give him many carrier bags of scrap wood so he knows what my hobby is.

he said his shotgun had a crack in the stock and he did not want to shoot it as he thought it was dangerous.

I removed the lock and saw the crack. I pulled gently on it to see if i could run some glue in it, and it just disassembled itself.

What are the (varying) opinions on how to stick this back together again?
Glue, epoxy, stitching?

 

[undergroundhunter]

Epoxy definitely. To be honest I wouldn't fire it again without a gunsmith looking at it and carrying out some sae test firings, it could be really dangerous.

Matt

 

[NazNomad]

A good PVA will make a joint that's stronger than the wood. I'd have thought epoxy would be a bit brittle?

 

[sunnybob]

This is the choice. Pva or epoxy?

Safety isnt a real issue, I've had firearms for well over 30 years and have shot stuff in almost as bad a condition. The main force of the shot is directly back into the good wood.
But this we are pretty sure, is why his scores have been poor for the last few months.
Luckily, as the stock is now considered scrap, it doesnt really matter what I do. I could even stitch it with wire.
A new stock is in the £500 range, so he will be happy with safe, and not too fussed with looks.

 

[Hot stuff]

Is making a new stock out of the question? I have no experience of guns, don't know what they're made of, just genuinely curious.

 

[NazNomad]

I wouldn't think epoxy was a choice, to be honest, and I reckon you'd see a glue line with it anyway.

Aliphatic resin is best, PVA is just as good for a gunstock really. It's not being left out in the rain, after all.

 

[sunnybob]

Almost all shotgun stocks are walnut. Making new is way beyond me. Fitting the wood to the lock is a very skilled job, and even shaping would take me a fortnight of painfull mistakes. The wood value is immaterial in this case, its the machining that costs the money.

I have D3 pva, or Titebond 3. or 2 part epoxy. Must admit I'm favouring titebond at this stage. This is bad enough that glue lines are irrelevant. the split goes right through the checkering, so its not going to be an invisible repair, no matter what.

 

[Racers]

Do you have the Titebond for dark wood, that would be my first choice, I would degrease the break and make some clamping blocks to hold everything in line.

Pete

 

[sunnybob]

I only have titebond 3. It leaves a dark line, but the walnut is quite dark anyway, and as said, looks are just not relevant to this repair. Its all about strength.

looking closely at the crack it appears to be quite an old start to it. my prying fingers just finished it off.
i think maybe a good clean with white spirit before gluing?

 

[thetyreman]

if it's about strength then definitely go with epoxy

 

[custard]

These kinds of angled splits are notorious for leaving big ugly glue lines. Epoxy or Cascamite have more pronounced glue lines to begin with, they're also thicker than PVA so they'll tend to hold the split apart slightly, making the glue line even more prominent.

The advantages of Epoxy or Cascamite are that they're slightly gap filling, so they can accommodate any small voids or misalignments, and secondly they don't need any complicated cramping arrangements. With PVA you'd have to ensure high pressure right out to the feather edge of the split, that in turn would probably require some kind of waxed caul.

Another thing to bear in mind, as time passes the exposed surfaces within the break will oxidise and become contaminated with dust. That will reduce the strength of any glue joint, but PVA probably suffers more than Epoxy or Cascamite in this respect.

There isn't a right or a wrong answer, it's as much about your particular priorities and resources.

 

[Beau]

I would go for a high quality epoxy like West System. The plain West resin has a low viscosity so leaves a very thin glue line and gets deep into the pours of the wood plus its gap filling ability if things don't go together perfectly.

 

[Orraloon]

I would encourage the use of epoxy for all the reasons custard mentioned. The quick set tends to be brittle so use the slow set. First use acetone to degrease the surfaces. The repair should be stronger than wood but the real issue and cause of the failure is the grain runout. Grain direction should have been more in line with the stock. A poor bit of wood selection in the first place. As said there is nothing to loose with a repair attempt and it may even last for decades yet.
As examples of the strength of epoxy I have repaired guitar necks that have snapped clean through and they are under a lot of string tension. I have also spliced wood billets together at the handle to make longbows. Again under quite a bit of stress. I did have a bow break on me but it was not at the glue splice.
Regards
John

 

[MusicMan]

Aerolite was tested under severe machine gun fire, both ways, in Mosquitos in WW2. Cascamite is a similar glue. So they would be my choice. A thin slow-cure epoxy would also be OK. As Custard says, the gap filling and ease of cramping (just duct tape wrapped around would work) would be my main considerations.

Keith

 

[sunnybob]

The majority opinion is epoxy then. Dont have cascamite or aerolite, so thats good to hear.

The gun is a Beretta, so it should have been a better piece of wood than it is.

As looks are no longer relevant, I might even inlet a brass strap and turn it into a name plate, it just depends how much time I get with it and if I can find screws small enough.
Thanks all.

 

[Eric The Viking]

Just a query: the dark, narrow hole that seems to run back into the split--does that have metal in it normally? If not (as in it's a leftover from the machining), could you put a neat cross dowel, possibly even two, in to strengthen it? It would have to go across that hole, hence my question, but it might alleviate the shear stresses on that awkward grain. With care it would look quite neat, and you'd have to re-finish the stock anyway, probably...

I do a lot of stuff in cheap softwood, and use cross-grain* dowels to strengthen end-grain fixings, that wouldn't work otherwise. I realise it's a different problem, but it would help with the shock stresses when the gun is fired.

E.
*obviously I mean that the dowels run across the grain of the main piece of wood, not that they themselves have cross grain like plugs you make with a plug cutter!

 

[sunnybob]

No, that hole is needed for the bolt that holds the lock to the stock. Impossible to fit even a small dowel across the split without actually weakening it.
Pins might work, thats why I'm thinking a brass plate so the pins have a purpose.

 

[Eric The Viking]

Ah. Shame. Thanks for explaining.

 

[beech1948]

Sunnybob,
I would really like to see the outcome of this if you have time to post it. Thanks in advance.

 

[MusicMan]

There's a technique used for pinning cracks in hardwood woodwind instruments that might help.

1. Get some threaded pinning rod for a musical instrument repair supply shop such as Dawkes.

2. Drill and tap a hole the right diameter for the thread. preferably blind but not too important. The thread should be tight fitting. It should have a small lead in at the entry side.

3. Measure the length of rod needed so that it ends up just below the surface at each end. Nick the rod with a small hacksaw, but not too deeply.

4. Screw the rod in to its final depth. The nick is below the outer surface but within the lead-in taper.

5. With a pliers, give the road a sharp bend across the nick. It will snap off there.

6. Mix powdered walnut (or whatever wood the stock is made of) with epoxy to a thick paste.

7. Fill the entrance hole (and exit if you drilled through) and allow to set hard.

8. Smooth and finish.

Such pins can be very nearly invisible. The purpose is not to pull the crack together but to hold it stable and stop it spreading. Thus you do this after glueing.

The holes are often drilled at an angle to the surface but I don't see a lot of point to this.


Keith