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Old 7th August 2012, 07:49 AM   #1
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Default Cabinet glued and clamped, but not perfectly square - now what?

I just finished building my first guitar amp cabinet. First time user of a dado blade set and cutting box/finger joints and they turned out quite nicely if I do say so myself.

However, I hit an amateur snag. Once the cabinet was glued and clamped I did some last minute checking and measuring and found that the cabinet wasn't perfectly square in all corners. One was out by about 1"

My dad and I managed to apply some pressure and get it to a very close 90 degree angle on all corners. I'd say 3 out of the 4 corners are off by no more than 1 degree, while it seems like on corner is slightly out by just a bit more.

If I use a machinist square to check for its dimensions, the one corner is off by roughtly 1/4".

Will this cause problems when mounting my speaker baffle, and later on for the internal acoustics of the cabinet itself and/or the resonance of the baffle?

Thanks for any and all advice,
Cheers,
Joel
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Old 7th August 2012, 10:25 AM   #2
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The old camel herder always said, "Only Allah is perfect.". (I actually don't know if he said that or not, but an old machinist told me that the old camel herder said that.)

You're quite ambitious to attempt finger joints - I admire you!

Without a dimensioned sketch of your cabinet I can't really say, but it sounds like your cabinet is usable. The misalignments don't sound severe enough to prevent sealing the joints with, e.g., battens and glue, some kind of caulking material, etc. In a theoretical sense it can only help the internal acoustics - without parallel surfaces it's more difficult to create internal standing waves.

If I understand your description, the only problem is you may have to carefully measure and cut your front baffle as a parallelogram rather than a rectangle.

Finish your project!

Dale
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Old 7th August 2012, 12:32 PM   #3
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You likely encountered a common problem in fabricating a long finger joint, the tradeoff between making the joints with with tight clearance vs. adequate clearance. When setting up and cutting the finger joint you like to use a fit that dry assembles fairly tightly. The problem is that by the time you can apply glue to all of the mating surfaces the glue begins to set while the wood begins expanding from the moisture in the glue and the thickness of the glue layers...making your "nice tight dry fit" finger joint a near interference fit that is very tough to close. I use finger joints for drawer box construction and find that a long finger joint (one with more than maybe 12 pairs of fingers) needs clearance of about 0.01" (0.25mm) to allow for these factors.

In view of these factors I would consider a finger joint to be very challenging to assemble for something as large as a speaker unless the pitch of the joints is widened to limit the number of fingers to 10 or less.
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Old 7th August 2012, 05:55 PM   #4
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Cool, thanks. Ya its a very minimal misalignment and once the internal battens are set in to attach my front baffle to there should be no problems (gaps etc.).

If you measure corner to corner the diameter of the cabinet you'll find 30" on one side and 29 3/4" diameter on the other side. Again, a very minor overstep.
But ya, i fully intent to keep going with this one and see it through to the end.

To be honest the finger joints weren't that difficult of an endeavour. Constructing a good jig likeTHIS ONE was the most time consuming part. Once it was fine tuned enough to get each cut identical it was just a matter of taking my time and making each cut one at a time with it. The joints fit together like a glove afterwards.

Cheers!
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Old 7th August 2012, 08:25 PM   #5
adason is offline adason  United States
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"Cabinet glued and clamped, but not perfectly square - now what? "

the question is, if no one is there, will it still produce the sound?
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Old 7th August 2012, 08:28 PM   #6
adason is offline adason  United States
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actually, if you think about it, it may even be better, for any symetry is not good for fr response
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Old 8th August 2012, 08:37 AM   #7
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Quote:
Originally Posted by joelostrom View Post
To be honest the finger joints weren't that difficult of an endeavour. Constructing a good jig likeTHIS ONE was the most time consuming part. Once it was fine tuned enough to get each cut identical it was just a matter of taking my time and making each cut one at a time with it.
Yes, there are quite a few plans available for jigs to do finger joints and dovetails. I recently made one for my router - took about 3 days to get the jig properly aligned, then about an hour to do the joint I built it for.

Dale
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Old 8th August 2012, 08:48 AM   #8
ODougbo is offline ODougbo  United States
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I've been to a few tool/trade shows, demonstrators are making them super fast (minutes) with table router jigs .

They are expensive and I don't have the patient, but it looked fine.
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