need some advice on re-glueing broken joint

[Dave Tesch]

i have a speaker box (store bought) made of particle board here in my shop. it was dropped on a truck (or off a truck, not sure) and it broke a glue joint and has some mild crush in a corner.

never in my life have i seen a proper glue joint break, so i assume this was not a well made glue joint. box is 3/4" particle board with angled butt joints. its a "wedge" shape box so it has 7 sides total.

i can pry a thin blade in the corner between the edge and i think i can get some glue in most of the edge, but not all of it especially where the joint has not yet failed. is there a way to "wick" glue into a tight spot? i am thinking of using titebond II as that is my glue of choice these days.

i would attempt to remove the entire side and redo all the glue but i think i may destroy the particle board attempting to remove it. i dont see any nails or staples. this thing was not built well but is otherwise a decent live sound speaker.

if i can get the joint glued tight then i can make a brace for the corner (out of real wood) and it should last another several years.

if you are into speakers the speaker is a yamaha sm115V and runs about $350. i dont have pictures of the damage yet. the speaker in the picture is the small angled box above the subs in the middle.

http://inlinethumb32.webshots.com/39647/2509645340026985969S425x425Q85.jpg (http://good-times.webshots.com/photo/2509645340026985969gjqbRn)

[Chip Lindley]

Dave, if you can pry the broken corner apart, a piece of wire can help push glue down into the joint as far as possible. Try not to break off bits of PB into the joint.

Consider using polyurethane glue (Roo Glue, Gorilla Glue, etc) instead of Titebond. The stuff really holds! If a wood cleat can be added to the inside of the broken corner, so much the better.

No reason your repair will not be as strong as the factory corners. Of course, you need to discuss this with your Roadies!

[Don Orr]

Dave-I am no highly experienced expert but that won't stop me from giving my opinion.:D

First of all I would use epoxy because it will stick to most anything including itself. There is probably still some of the original glue in the joint and if you can't clean it off to bare wood(PB) then Titebond will not be your best option. Also since you can get the joint apart a little you can put the epoxy on the inside of the joint and use a shopvac to draw it into the joint from the outside. Clamp it up and let it cure and you're done. If the epoxy you use is thick, it can be thinned with a little alcohol, acetone or lac. thinner. Common technique for a common problem.

[Van Huskey]

I have used something like the below in similar repairs, not a do all wonder cure but it does help more than anything lese I have tried.

http://www.garrettwade.com/product.asp?pn=08S01.01&bhcd2=1276022945

[Glen Butler]

Cyanoacrylate comes in different viscosities one of which is like water and will wick into anything. Problem with the glue being that thin is getting body to it. But tightbond's medium is thin enough to wick but still has body.

[David Thompson 27577]

What Don said....

Use Epoxy. Do whatever you have to do to get the epoxy into the joint. Then clamp it, and wait 24 hours.

[Dave Tesch]

thanks for the responses. further inspection reveals that at least 6 joints have broken, mostly along the glue. one edge has partially torn out an adjacent board along the joint but other than that it is all the glue joints that have broken.

i figure the best option at this point is to try to take the back two pieces off the box and reglue them. there are some nails, look like 2" staples or brads possibly 16 gauge in various spots. since the back two pieces are mostly loose anyway they should come out if i can cut/break the nails.

i did get a second opinion; i called up my good friend who is an actual carpenter (rather than a utility carpenter like me) and his suggestion was to remove the small end piece first, as if i broke it (likely) i could easily cut a new one out of plywood. if that piece were missing it should be a lot easier to get the larger back pieces out.

both he and i agree i would be better off with a new cabinet made from 3/4" ply but at this point my employer is not willing to go that far. i've done that kind of work and the hours involved getting it just right are plentiful.

i'm a little frustrated at the way this box was made; i suppose you get what you pay for but the better boxes are all made with dado joints and have braces on the inside in addition to being made from baltic birch. i would guess you could drop one of those and have it survive. this box is all butt joints and it looks like the front is not held in a dado, but just stuck there and brad nailed. not sure on that though.

if i can successfully get the two panels out and can clean up the edges, should i go ahead and use titebond II or use the poly type of glue? should i use a couple brads, or drill some countersunk holes for a few screws? or is clamping and no nails/screws my best bet?

[Eiji Fuller]

tighbond 2- squeegee it in with your fingers and force it in with compressed air, repeat, clamp, done, reinforce on the inside if possible.

I would stay away from poly glue. Weakest glue on the planet!

cyano acrylate is good for little stuff but is too brittle to make a strong joint unless there is good contact and plenty of glue surface.

[Stephen Cherry]

http://www.westsystem.com/ss/filler-selection-guide/


I would consider epoxy with a filleting filler. This is well known in the boat building areas for increasing joint strength. The concept is thicken the epoxy into a mayonnaise consistency, and glue the parts together. Then you add a bead of thickened epoxy where the parts meet and use a rounded flat piece of wood with the right radius to shape the bead into a fillet.

better explanation:
http://www.westsystem.com/ss/bonding-gluing-clamping/

[Don Orr]

Dave-as a follow up now that you have added more info, I would avoid Titebond on Particle Board. Not because of the glue but because of the compostion of the material. The particles in the board usually separate before the glue does. This would also happen if using epoxy. If you don't get rid of all the old glue, new glue will not adhere very well, where as epoxy will. A few carefully placed screws with predrilling might add significantly to the strength of the joints.

Good epoxy, like the West System products, is easy to work with, can be thinned or thickened and is available easily. They have great info on their website as Stephen C. showed. Make sure you use some kind of gloves when working with epoxy. Nitrile are best but others work.

[Harold Burrell]

Duct tape.

(Not really. I just wanted to be part of the discussion and say something different.) :o

[Ben Hatcher]

Dave,
I'd avoid taking it apart at all costs. You'll end up with a huge mess and cause more work for yourself. Your local big box store will have screws specially made for particle board and MDF. Put a few of them along each side using pre-drilled holes. They should have large faces to spread their holding power across more surface area.

Alternatively, screw and glue cleats into the joints from the inside of the boxes.

[Howard Acheson]

Do not attempt any repair with PVA (Titebond) adhesive unless you can get all the old adhesive completely off the joint. PVA adhesive relies on adherence to bare wood for good bonding.

Slow set two part epoxy is your best choice.

Speaker boxes require strong, tight joints for the best sound.

[Dave Tesch]

i have given up on this box, it fell apart while i was working on it this morning. it just gave out and all the joints in the entire box let go. it is a pile of boards at this point. literally i pulled the pieces apart with my hands, what a pile of junk.

i actually cant find any glue on this box. i did find some odd sticky clear stuff in one spot but that is it. i am wonering if they used tape or something, but not glue - no evidence of glue.

i am going to take the pile of boards and copy each piece with 3/4" plywood and make a new box that is a copy of the original. it just isnt worth trying to reuse any of the particle boards. the hardest part will be the dado cuts and getting an accurate measure of the angles used on the edges.

i will add at least two braces to the new box, as this size of box really does need some bracing inside.

thanks for all your help.

[Tom McMahon]

You might not have to take your speaker apart. Water thin CA will wick into a joint at least 3/4 of an inch and sometimes farther. I have done repairs where I even pre-clamped the joint then ran a bead of CA down the inside of the joint and gotten complete penetration of the joint. I usually go over the joint several times until the glue soaks in slower.

[Stew Hagerty]

I would definately use epoxy as it will stick to the previously glued surfaces better than a wood glue will. As for working it down in. I have found that the thin end of a zip tie (cable tie) is perfect. It is stiff enough to not ben and yet thin enough to spread the glue deep into the recesses you can't otherwise reach. Plus, individually, they cost virtually nothing.

[Cliff Rohrabacher]

from the extent of the damage you describe It might be better to just build another enclosure.

[Dave Tesch]

sigh. i dont think they are supposed to come apart like this.

http://inlinethumb36.webshots.com/45923/2783033770026985969S500x500Q85.jpg (http://outdoors.webshots.com/photo/2783033770026985969Lzlqky)

notice how only the joints came apart, like there was no glue in the first place. amazing.

i did a cut sheet and it looks like a full sheet of ply will give me enough for two boxes.

[Dave Tesch]

here is an update:

http://inlinethumb28.webshots.com/45083/2665920720026985969S500x500Q85.jpg (http://outdoors.webshots.com/photo/2665920720026985969nKulbi)

its not perfect, nor my best work. i have to be conservative with my hours on this project.

i do have to say, a 7 sided box pushed my limit on skill level. its hard to get all the pieces to fit together right, even though i copied the pieces exactly. the boards moved a little after i cut them just like they always do, but i have enough experience with 6 sided boxes that i can manage some movement.

i made two boxes, they are about 1/16" off from each other. i'm thinking these wont have the same issues as the particle board ones did :D

[Steve Bracken]

here is an update:

http://inlinethumb28.webshots.com/45083/2665920720026985969S500x500Q85.jpg (http://outdoors.webshots.com/photo/2665920720026985969nKulbi)

its not perfect, nor my best work. i have to be conservative with my hours on this project.

i do have to say, a 7 sided box pushed my limit on skill level. its hard to get all the pieces to fit together right, even though i copied the pieces exactly. the boards moved a little after i cut them just like they always do, but i have enough experience with 6 sided boxes that i can manage some movement.

i made two boxes, they are about 1/16" off from each other. i'm thinking these wont have the same issues as the particle board ones did :D

Decent looking box, but you have now completely changed the sonic characteristics of what was a very good speaker.

The speaker failed not because it was a bad box, but because it had been severely abused, way beyond what it was ever meant to take.

All is not lost, but you have to rebuild with the same materials as the original if you ever want to match it with a partner. Particle board is used because of it's mass. It's only real issue is if it gets wet, or dropped heavily, as you found out.

If it was mine, I would use the old pieces as a pattern, and rebuild with particle board the same thickness and density as the original.

just my 2c