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Gluing up lock-miter joints on plywood carcase

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Forum topic by GregD posted 06-06-2010 05:09 AM 4728 views 0 times favorited 9 replies Add to Favorites Watch
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GregD

623 posts in 1824 days


06-06-2010 05:09 AM

I am making what I thought would be a fairly simple plywood cabinet with drawers – 30” tall, 20” wide and 27” deep. Because it will be on wheels I’m using 3/4” plywood for the sides, back, and top. While I plan to use pocket hole screws on the other parts of the carcase, I decided to use a lock miter to join the sides, back, and top.

The lock miter joints did not glue up as tight as I would have liked. The joints needed a bit of clamp pressure to pull tight on the dry fit, so I probably would have had better results if I had worked faster or used a glue with a very long setup time like Gorilla glue. Any other suggestions for getting a better glue up? Any suggestions for getting longer working time with yellow glue? I’m using the “long work time” Titebond, but it still starts grabbing pretty fast. I suspect it wouldn’t grab so fast if I thinned it or even if I wet the joint before spreading the glue, but I was concerned that might weaken the glue bond.

Also, any suggestions for filling the cracks at the miters? My best idea is to try and work some wood filler in them and hope they become less noticeable. Another idea that would also make the corners wear better would be to chamfer the corners – maybe 1/4” – and glue in some solid stock that could take a 1/8” roundover.

Thanks in advance!

-- Greg D.


9 replies so far

View a1Jim's profile

a1Jim

112316 posts in 2265 days


#1 posted 06-06-2010 05:58 AM

Greg the best patch for wood is wood so just glue some slivers of wood in the cracks let dry and then trim and sand. filler almost always looks bad unless it gets painted.

-- http://artisticwoodstudio.com Custom furniture

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RZH

73 posts in 1797 days


#2 posted 06-06-2010 06:12 AM

I would suggest glue only as many panels as you feel cormfortable handling. Assemble the rest of the panels dry, without glue, then make sure everything is square, and let dry. Repeat…

-- Ron

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GregD

623 posts in 1824 days


#3 posted 06-06-2010 07:10 AM

Ron – sad to admit it but I glued 1 side to the back on the first pass, and then the other side to the back on the second pass. The was the third pass and there was no choice – it fit into the other 3 parts all at once. Next time I guess I’ll try Gorilla glue and a bigger stack of clamps.

Jim – OK, so maybe I shouldn’t bother with the wood filler. I think I could fill the cracks with splinters well enough. Still, I don’t really like the sharp corners either, and if I’m going to fuss with the corners I’d like to do something about that too. What about a small chamfer on the corners and then iron-on edge banding? I suppose that might look strange on the corners that run cross grain on both surfaces.

-- Greg D.

View Julian's profile

Julian

880 posts in 2213 days


#4 posted 06-06-2010 03:24 PM

try slow setting titebond glue. poly glues like gorilla glue are too messy for me.

-- Julian, Park Forest, IL

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richgreer

4524 posts in 1763 days


#5 posted 06-06-2010 04:24 PM

There is a big difference between regular Gorilla glue and Gorilla Wood glue. I never use regular Gorilla glue on a wood working project – to messy and too hard to control.

Of the readily available glues available, Tite Bond III has the longest open time.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View Jim Crockett (USN Retired)'s profile

Jim Crockett (USN Retired)

852 posts in 2421 days


#6 posted 06-06-2010 06:04 PM

Greg, for future reference, if you need long open times for glue-ups, you should try either hide glue (in a bottle, not the melt type) or urea resin (weldwood, etc.). Both create a good bond and have 20-30 minute open times or greater depending upon the temperature and humidity.

Jim

-- A veteran is someone who, at one point in his/her life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including his/her life".

View RMR's profile

RMR

10 posts in 1602 days


#7 posted 06-06-2010 06:25 PM

I had the same disappointing results recently with locking mitre joints on fairly large plywood panels on some casework. Some drew up nicely and others were open at the edge 1 -2 mm. Fortunately it wasn’t critical on the piece I was building but I’d prefer to get it right regardless. I used a water based wood filler and, once the sharpness of the corners were relieved a bit with sanding, it wasn’t that noticeable. I top coated with lacquer and it’s okay for the application.

The chamfer idea may work but you will double your opportunity for noticeable seams. If you do something like that make it bold enough to be part of “your new design” so it doesn’t look like a repair – just my opinion. Try the filler first, it doesn’t foreclose your options for something else if you aren’t happy with the results.

I was a little gun shy about using locking mitre joints again, at least on a long joint in a plywood panel (aren’t they ‘fun’ to set up?). Next time I’ll try a glue with a longer open time – I was using Titebond I. In hindsight, that was my problem. Thanks for the advice.

-- Bob, Kent, WA

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GregD

623 posts in 1824 days


#8 posted 06-06-2010 06:58 PM

Jim – I’ll look into those glues. Thanks.

RMR – I didn’t have much trouble setting up the bit. I was able to “dial in” the height in a few minutes using a digital caliper, digital height gauge, and a high-end router lift. Setting the fence was a bit more of a hit-and-miss process. Thanks for your thoughts.

-- Greg D.

View Ger21's profile

Ger21

671 posts in 1819 days


#9 posted 06-06-2010 08:06 PM

I’d route a 1/4”x1/4” rabbitt and glue a piece of hardwood in there.

-- Gerry, http://g-forcecnc.com/jointcam.html

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