Butt joints,wood glue strong enough?

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I had trouble when I mitre jointed my cabinets using 18mm (three-quarter inch) ply. I wanted the layers to be visible around the baffle so as to be part of the design and then to keep the cabinet natural looking but piano lacquer the baffle. @caused a bit of stress and still haven't managed to do it properly. I have a strap type mitre clamp by Stanley (for picture frames though) and a couple of fully adjustable sliding 'sash' clamps I think they are called but I need to do some remedial work and would really appreciate some guidance here !!!!!! I want a completely strong and airtight seal and have added some fixed 'guides' internally to keep everything in place, if you know what I mean. Any tips appreciated

Thanks
Gareth
 
I had trouble when I mitre jointed my cabinets using 18mm (three-quarter inch) ply. I wanted the layers to be visible around the baffle so as to be part of the design and then to keep the cabinet natural looking but piano lacquer the baffle. @caused a bit of stress and still haven't managed to do it properly. I have a strap type mitre clamp by Stanley (for picture frames though) and a couple of fully adjustable sliding 'sash' clamps I think they are called but I need to do some remedial work and would really appreciate some guidance here !!!!!! I want a completely strong and airtight seal and have added some fixed 'guides' internally to keep everything in place, if you know what I mean. Any tips appreciated

Thanks
Gareth

I never had any luck with band clamps on large boxes. There is made an oversize version of a corner clamp by Bessey (I think.) It comes the closest to holding a corner true. The best results come from machined joints such as a rebate cut.

I just built a porch with mortise and tenon joints. Took half a day to prep the pieces. Fifteen minutes to frame it up! Saved about $60 in steel braces! Because the mortises were template routed ant the tenons dado cut everything went together square.

With fewer tools then clamping blocks in place then glue and nails is a very good method.

Once glued up badly wood filler, stain and markers can fake the look.

Also when you sand through the veneer a bit of stain carefully mixed will hide your mistake.

Painted boxes are often built with the rebate (dado) cut slightly deep so the edge sticks up. It is then sanded flush to look like the joints were cut perfectly.
 
I love the Kreg pocket screws. The single best thing about them is that you can easily disassemble a joint. That's not so useful for speaker cabinets, but when I discovered that one of the kitchen cabinets I built was 3/4" too wide for the space, it took me all of 30 minutes to disassemble the cabinet, cut the 3/4" out of the top, bottom, back and door of the cabinet and reassemble it.

As for filling nail holes, I've used home-made wood filler using wood dust from my sander and yellow glue. It's messy, but it's cheap and quick. However, I'm thinking of trying to use auto body filler just to see how it works, especially for any larger gaps.

I have never had luck with mitered corners on bigger boxes. They are hard to cut accurately (the only reliable way I've found is to use a table saw sled with stops to manage length), they move around when you try to glue and clamp them and, if your pieces have any issues with warpage (see my screed about $&#$^# cheap plywood), they will not come together tightly.
 
I often use butt-joints in my building. With good clamping, they're as strong or stronger than the base materials.

I am currently working a pair of dressers into sub cabs. Don't laugh, the tops are 2.25" thick mdf, one side is 1" mfd and the other two sides 3/4", all glued and screwed- hence why they're being recycled, there's about $70 in MDF free as a starting point. Front and back are new plywood from me, as drawers and 1/8" fiberboard don't make good panels.

In reworking them to my purpose, I've been adding lots of internal bracing- scrap plywood cut to fit. Clamping would be a nightmare inside the middle of a deep cab like that, so I'm using pressure from the braces. Essentially, they're press fit with other cut braces pressing them into place while the glue cures. Between these and wedging some shims in, the glue is working beautifully.

Lots of clamping pressure is desirable, but you'd be surprised just how much a little wedge action can get you. Also remember, that while strength is very helpful, we're not talking about high energy transfer here, cabinet vibrations are relatively small so it doesn't take a lot of outright strength. Sometimes just laying (flat) pieces in with glue and pressing them into place is sufficient for strengthening a cabinet. A proper designed bracing system isn't always an option, particularly if you're fond of recycling cabinets (as I am).
 
Yeah I see what you mean, Getting the mitres to sit nicely is a problem. Whilst I have cut them nicely, taking my time to set up the saw blade and checking twice and working once, it is a pain to bond the full length of the mitre perfectly. I have inserted some 1" x 1.5" around the insides to help alignment, bought another mitre strap clamp then used some extra pieces of wood between the clamp and the speaker itself, making sure to get rid of any glue beforehand and then tightened the clamps and the woodscrews I have inserted all-round inside to help.

Seems o.k. and they are super sturdy. Fit the internal bracing next and then insert the 1" MDF baffles inside the front and the dual 18mm (3/4") sandwiched back to the cabinet and job done. Not forgetting the crossover and some stuffing.
 
Yeah I see what you mean, Getting the mitres to sit nicely is a problem. Whilst I have cut them nicely, taking my time to set up the saw blade and checking twice and working once, it is a pain to bond the full length of the mitre perfectly. I have inserted some 1" x 1.5" around the insides to help alignment, bought another mitre strap clamp then used some extra pieces of wood between the clamp and the speaker itself, making sure to get rid of any glue beforehand and then tightened the clamps and the woodscrews I have inserted all-round inside to help.

Seems o.k. and they are super sturdy. Fit the internal bracing next and then insert the 1" MDF baffles inside the front and the dual 18mm (3/4") sandwiched back to the cabinet and job done. Not forgetting the crossover and some stuffing.

Investigate the biscuit joiner (plate joiner.) You can angle the fence to cut on the mitered faces. The biscuits will hold the joint in position while you clamp making perfect registration very easy. The resulting bond will be very strong.

The only screws I use hold the drivers and the wire cups.
 
a spline the length of the miter keeps it aligned. Leave the blade angle set after you cut the miter. lower the blade and flip the piece. check your fence and cut the groove. My blade is 1/8" but if needed you can carefully adjust the fence to make a slot any thickness you wish. !/8" ply or pressboard makes a good spline.
 

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a spline the length of the miter keeps it aligned. Leave the blade angle set after you cut the miter. lower the blade and flip the piece. check your fence and cut the groove. My blade is 1/8" but if needed you can carefully adjust the fence to make a slot any thickness you wish. !/8" ply or pressboard makes a good spline.

Given your illustration, the spline would obviously be better but lacking CNC wouldn't that approach be impossible? <I like making things myself.>

P

As well, how much stronger <compared to performance> could the spline be verses biscuits? I guess you have the CNC people make the splines also?
 
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My original point was I used biscuits and butt joints with good success in the beginning. CNC isnt a magical place where evertthing is perfect. Things still need to be fitted together and "worked". I wont lie...it is nice b]ut with it comes a brand new set of problems. Personally I wouldn't do a mittered edge...there is too much that can go wrong. I bite the bullet and get a dado set, some good pipe clamps and if budget allowed a pneumatic stapler. I have had way better results with staples than with brads.
 
Semi OT, forgive me:

In reworking them to my purpose, I've been adding lots of internal bracing- scrap plywood cut to fit. Clamping would be a nightmare inside the middle of a deep cab like that, so I'm using pressure from the braces. Essentially, they're press fit with other cut braces pressing them into place while the glue cures. Between these and wedging some shims in, the glue is working beautifully.

Lots of clamping pressure is desirable, but you'd be surprised just how much a little wedge action can get you. Also remember, that while strength is very helpful, we're not talking about high energy transfer here, cabinet vibrations are relatively small so it doesn't take a lot of outright strength. Sometimes just laying (flat) pieces in with glue and pressing them into place is sufficient for strengthening a cabinet. A proper designed bracing system isn't always an option, particularly if you're fond of recycling cabinets (as I am).
Just adding a pic to clarify- couple more braces away from "done" but you get the idea.

An externally hosted image should be here but it was not working when we last tested it.
 
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