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What is the minimum amount of time you would leave a back joint glue up in clamps before thickness sanding it?
Thanks

A couple hours unless it's humid or cold. Then I would double it.

I class thickness sanding as subjecting the joint to stress, and normally clamp for a couple of hours, then let it sit for 24 hours total drying time before "final" thicknessing.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Concur with Colin on this one. If the joint is to be worked or stressed 24 hrs after gluing.No scientific reason,just insurance.
Tom

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A person who has never made a mistake has never made anything!!!

Also I would not glue up in cold or damp conditions, just asking for trouble.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

it depends on glue used. Tite bond you can work on after an hour. I have used fish glue ( 2 hrs and hot hide glue ) CA in about 10 minutes.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Sorry, I should have been clear - I was talking titebond original, and I am just following manufacturer's recommendations.
There's usually plenty other things I can be doing while plates are being glued together- cutting braces, initial sizing of them, thicknessing sides, bending them, making end blocks, bindings, rosettes etc. so I don't see any point in pushing one particular process.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

John, I think you mean 12 hours for the fish glue? IIRC, they recommend a 12 hour clamp time on it.

I would just double the manufacturer's recommendations. They say about 1/2 hour clamp time for Titebond, so I'd wait maybe an hour. You don't stress the plate all that much thickness sanding it, not unless you're trying to take off a lot at once. Just take light passes and you won't be heating up your fresh glue joint too much.

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

I have thicknessed fish glue after 2 hours without any problem . I do reclamp after thicknessing.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Titebond and 24 hrs. for me.

I set the timer for 45 minutes and start working in after that...with Titebond.

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Thanks all...

It is less dramatic for hardwoods, but for soft woods I like to wait overnight before thicknessing. Otherwise, when the moisture from the glue completely evaporates, the centre seam can become slightly thinner than the surrounding area. This is valid for PVA or HHG, or any water based adhesive. No such issue with CA, epoxy or polyurethane.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I've noticed that with rosettes for sure.

I give rosettes 3 days.

I give it an hour or two and then start carving. The bottle says 24 hours before stressing, but again, living in AZ the glue dries up so fast that the bond sets much faster. On a neck/fretboard glue up, I give it overnight because it's alot of glue in a confined space, but everything else comes out as soon as the glue run off has hardened and turned yellow. I have never had a seam break on me either using the impatient method I am describing.

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http://www.sixgunguitars.com

1 hour , 45min, .....
there are brave men here!

I would think with some glues the wood would pick up moisture and need some time to dry. The glue might look dry on the outside, but not so inside the joint. So that's why i give it the extra time. Better to be safe than sorry when it comes to joint failure.

I've always been a 24 hour guy myself. I'd rather not get in a hurry to ruin something or waste my time.

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"Act your age, not your shoe size" - Prince