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Campfire Greenhorn
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Campfire Greenhorn
Joined: Aug 2009
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I find myself in the process of repairing a laminate stock with a hairline crack in the wrist. I read somewhere that Thinned Acraglas was an excellent adhesive to make this repair with.
What do I use to thin Acraglas?
Any suggestions on a better product to repair a small crack where getting the glue to penetrate is the key?
thanks,
TK
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Campfire Outfitter
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Campfire Outfitter
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Heat it, or heat the work piece. A hair dryer will work. At some point it will turn watery, then you have to work quickly before it begins to harden. I have repaired cracks by loading Acraglas into a hypodermic syringe and injecting it into the crack. You can apply the hair dryer to the syringe. Sometimes you can use a small drill just larger than the needle to drill a blind hole.
Paul
Stupidity has its way, while its cousin, evil, runs rampant.
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Campfire Outfitter
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Campfire Outfitter
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Heat.
Paul has some good ideas. A syringe and a small drill will help ensure you get at the guts.
You should warm the stock as well, almost to scary hot, no more than about 130-150, depending on your tolerance. Hot enough to burn you is too hot.
Get yourself some decent rubber disposable latex gloves. One of the things I do with cracks is finger-force hot, wet goo into the crack. It's kind of messy. But the hot stuff releases bubbles fast.
You can protect the surrounding area with masking tape, either blue or white, so you don't spill everywhere. Then when you think you have the crack filled, clamp it good, then make one last pass with the heat to liquify what is on the surface and wipe that off.
Depending on where the hairline is, I would consider dowelling, too. In fact, with a little planning, you can massively strengthen the wood, get more epoxy where it needs to go, and have the dowel looking like some kind of factory accent. Stylish.
Reason I know this is because I shattered an H-R sporter stock when I blew up my favorite 98.
After I realized I'd almost killed myself but was not dead, I went about the salvage job.
Aside from the action, I managed to recycle everything bent and twisted into another rifle, which took lots of epoxy and dowelling through the grip area and forend. But it doesn't look too bad after all -- almost looks like I PLANNED it to look like it does. Most important, it shoots fine.
Up hills slow,
Down hills fast
Tonnage first and
Safety last.
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Joined: May 2005
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Campfire Ranger
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Campfire Ranger
Joined: May 2005
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Hard to see how a crack could be in more than one lamination in a properly made stock. Anyway, I use paste wax on the wood surrounding a repair. Works as a release agent to make it easy to trim excess glue and pop off "oopses" with a fingernail. Careful to not get wax in the crack where you want the glue to stick, I don't heat the stock which would make that problematical.
The key elements in human thinking are not numbers but labels of fuzzy sets. -- L. Zadeh
Which explains a lot.
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Joined: Feb 2001
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Campfire Kahuna
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Campfire Kahuna
Joined: Feb 2001
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Heat.
Paul has some good ideas. A syringe and a small drill will help ensure you get at the guts.
You should warm the stock as well, almost to scary hot, no more than about 130-150, depending on your tolerance. Hot enough to burn you is too hot.
Get yourself some decent rubber disposable latex gloves. One of the things I do with cracks is finger-force hot, wet goo into the crack. It's kind of messy. But the hot stuff releases bubbles fast.
You can protect the surrounding area with masking tape, either blue or white, so you don't spill everywhere. Then when you think you have the crack filled, clamp it good, then make one last pass with the heat to liquify what is on the surface and wipe that off.
Depending on where the hairline is, I would consider dowelling, too. In fact, with a little planning, you can massively strengthen the wood, get more epoxy where it needs to go, and have the dowel looking like some kind of factory accent. Stylish.
Reason I know this is because I shattered an H-R sporter stock when I blew up my favorite 98.
After I realized I'd almost killed myself but was not dead, I went about the salvage job.
Aside from the action, I managed to recycle everything bent and twisted into another rifle, which took lots of epoxy and dowelling through the grip area and forend. But it doesn't look too bad after all -- almost looks like I PLANNED it to look like it does. Most important, it shoots fine. 130 is MUCH too hot! Getting the temp to 110 down deep inside the wood is about as hot as you want or need to go. Hotter and your epoxy will always set before you can get stuff together and aligned. Getting the wood hot and applying a bit of excess epoxy works well IF you add a layer of plastic wrap. The plastic seals the area and allows the cooling wood to "suck" the epoxy down into the crack/break. Doweling works if you have the jigs to hold the stock properly. art
Mark Begich, Joaquin Jackson, and Heller resistance... Three huge reasons to worry about the NRA.
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Joined: Nov 2005
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Campfire Ranger
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Campfire Ranger
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Any more heat than a seriously hot summer day and you are degrading the bonding and the tensile strength of the epoxy. Don't be heating that stuff up with a hair dryer to 130-150 degrees! You might as well save the money and use Elmer's Glue for all the structural integrity the epoxy will provide.
"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty
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Campfire Regular
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Acetone will thin AcraGlass!
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Joined: Nov 2005
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Campfire Ranger
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Campfire Ranger
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Yes it will, but thinning epoxy with any kind of solvent degrades its structural integrity as much as heat does, if not even more so. If your end use of epoxy is as a sealer coat on wood you can get away with those tricks (sort of, as heat promotes bubbles in the dried film from more dramatic out-gassing). If you intend to use it as a glue or bedding compound, absolutely not. This I got from engineers representing various epoxy manufacturers who would conduct tutorials in our shop on the use and properties of the stuff, since we were using hundreds of gallons of epoxy per year building boats and their reputations were on the line as much as ours. Naturally we had to prove them wrong, but only succeeded in proving ourselves wrong.
Last edited by gnoahhh; 02/22/11.
"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty
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Joined: May 2003
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Campfire Outfitter
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Campfire Outfitter
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Well, I confess I don't use a thermometer. I go with "ow" hot, warm enough to get good flow and haven't had trouble. Used to fix wrecked skis, including my own, and never had a fix pop unless it hit another boulder, this over a period of several years and several hundred repairs.
But yeah, I defer to the structural layup professionals. Boats can sink.
Up hills slow,
Down hills fast
Tonnage first and
Safety last.
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Joined: Jan 2001
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Campfire Ranger
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Campfire Ranger
Joined: Jan 2001
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You'll have to get with the manufacturer of your epoxy to find out at what temp you'll have problems with the epoxy curing. It actually takes an elevated temperature during cure to get the majority of the hardener and resin to complete their molecular bonding, so heat is a good thing, just not too much or it'll cure before it's completely bonded to what you want to glue together. Also cured epoxy softens at elevated temperatures.
The only reason to use a "thinner" with epoxy is to remove it from places you don't want it to go. Mixing a thinner in the epoxy will weaken it, heat should be sufficient to get the epoxy to get into the spaces you need it to go.
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Campfire Outfitter
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IF you can get ahold of the maker....sometimes their support sucks unless you just bought a carload lot.
In general, though, some heat is good to make your initial mix and get the bubbles to the surface. And it's also good to put your work someplace "warm" to cure. Like on a high shelf or in the furnace room.
Whatever the case, epoxies are wonderful stuff.
Up hills slow,
Down hills fast
Tonnage first and
Safety last.
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Joined: Nov 2005
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Campfire Ranger
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Campfire Ranger
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Yep, where would we be without it! I've spent so much time around epoxies that I'm starting to develop an intolerance/allergy to it. Small batches are ok, but if I'm around bucketful's for any length of time my skin starts to break out.
Did I tell you about the time one of the guys in the shop forgot to close the spigot on a 50 gallon drum of West System resin? You haven't lived until you tried to clean up a 20 foot wide lake of the stuff. Or the time a guy dumped resin into the hardener pot, and vice-versa, on a bulk epoxy mixer? Thank God it wasn't me as those were two very expensive mistakes!
The main word of advice I give people messing with the stuff is don't thin it, and don't heat it. Let it do it's thing.
Also, when working with thickened epoxy (such as when bedding a rifle) wet out the area first with un-thickened stuff (give it a couple minutes to soak into the wood), then mix the thickener into the remaining epoxy, and apply. You'll get a little better bond.
"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty
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Campfire Outfitter
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Noah, I'm curious if you have any experience with heat-sink epoxy. I have a problem-child sporter barrel that was chambered cockeyed. Read an old NRA short article, some guy had put a sleeve around his Springfield barrel, filled it with two-part, and halved his groups.
So...I cut threads on the muzzle, made a tension nut, found some conduit...that was before I thought to check the chamber for runout.
What I plan to do is cut away the bad section and rechamber it properly, then procure some electronics heat-sink goo and EXPERIMENT. I want the transfer of heat, not insulation. I have mold release so will try it unbonded without tension first, maybe a glue-in later.
Up hills slow,
Down hills fast
Tonnage first and
Safety last.
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Joined: Nov 2005
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Campfire Ranger
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Campfire Ranger
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I honestly don't know. Never worked with it. So, in effect, the guy in the article made a kind of bull barrel using epoxy around the issue barrel? If that's so, and it worked, I would think that maybe your experiment might work too. Nothing hurts a try but a failure! Of course, setting back and rechambering might make fooling around with epoxies a moot endeavor.
Carrying it one step further, I wonder how a fibreglass cloth (or carbon fibre)+ epoxy layup around a barrel would work. Build it up thicker than wanted, then turn a straight bull barrel taper in a lathe? God what a mess that would make! And the cloud of fibreglass dust swirling over the lathe? Whoo-boy!! Of course, in the end you would gain a modicum of added rigidity and some heat transfer (and a very funky looking barrel) but would there be a sufficient increase in accuracy to justify the hassle? And would the epoxy stay bonded to the barrel for a lifetime of thousands of shots? (I'll bet it would.) I know of at least one custom gun manufacturer (Christianson?) doing a carbon fibre barrel with a thin steel tube liner, but this would be a little different.
"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty
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Campfire Ranger
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Campfire Ranger
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So, in effect, the guy in the article made a kind of bull barrel using epoxy around the issue barrel? Sounds more like a composite structure. structural (tube) - core (epoxy) - structural (barrel). Would add substantial stiffness but guessing you're getting into diminishing returns past a heavy target barrel. Interesting concept though as the core material doesn't need much strength. Microbaloon/epoxy filler? Would be a insulator though. Haven't worked with heat sink epoxy (in electronics) after looking at the small quantity pricing. Staying with silicone pads or the zinc oxide crap. Or add fins radially like I beam construction. Now that would be a bear to fabricate!
The key elements in human thinking are not numbers but labels of fuzzy sets. -- L. Zadeh
Which explains a lot.
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Campfire Regular
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I've worked with heat sink epoxies. The problem with them is that they are about 10 times less heat conducting than steel. The best ones are silver filled, which makes them very expensive. Carbon fiber is about 10 times more conductive than steel, but when you put it in epoxy it goes to about 10 times less than steel. Additionally, carbon fibers conduct the heat along the length of the fiber, not through it, so you really don't gain an advantage for what you have in mind.
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If you aer using brownnell's acra glas they sell a thinner for it works real well on stock splits like you describe make the mix a little thin and i uas air to blow the stuff in the crack (30# ) or so and tape or wrap with rubber tubing and let sit over night
there is no man more free than he who has nothing left to lose --unknown--
" If it bleeds we can kill it" Conan The Barbarian
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Campfire Outfitter
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I don't want the insulation, of course. Maybe I should use Jello! That's almost a water jacket, right?
You are right about the spendy part. I looked, and the "fastest" stuff in terms of heat conductivity was like 50 bucks a half pint.
I'm still gonna do this....
The idea being, if it works, then those featherweight takeoffs at the gun shows become potential.
Up hills slow,
Down hills fast
Tonnage first and
Safety last.
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Campfire Regular
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Campfire Regular
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There's a company that I read about that's doing basically what you want to do - http://www.teludynetech.com/ . For epoxy you might look at Devcon Aluminum Putty (F). It's probably the best tradeoff of cost and performance for what you want to do. They also have an aluminum liquid, but I'd guess there's less aluminum in it, so not as conductive as the putty. I use the Plastic Steel Putty for bedding, and it's about the consistency of peanut butter. A little heat will lower the viscosity some.
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Here's the stuff to use: www.brownells.com/.aspx/cid=0/k=Acc...y/Products/All/search=Accraglass_thinnerEpoxy injection uses pressure to force the material into cracks. You may want to widen the crack a bit with a narrow saw blade on a Dremel tool, then use a hypodermic syringe to force the material into the crack.
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