24 Hours of Clamping

During the day I leave the clamps on for an hour and I often leave the clamps on overnight if I am working into the evening.

I see no reason why a cutting board should be different than any other clamping operation.

FYI – I think not machining for 24 hours is a very important directive.

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

I often “cheat” and wait 1 hour before taking clamps off if I am pressed for time (and need the cleamps) and 3 hours if I can.
As for not machining for 24 hrs… rules are made to be broken… and I have broken this rule many times without adverse consequences… well, maybe once or twice I’ve had to re-glue something but not very often and only in a complicated glue-up.

-- Don't let the perfect be the enemy of the good.

A lot of “conventiional wisdom” is really just urban myth – i.e. not supported by any real facts.

Your post addresses two glue parameters – set time, and cure time. Set time is the time it takes the glue to hold well enough for the pieces to stay put after the clamps are removed. Cure time is how long it takes the glue to cure enough to hold the pieces in place while being used.

Most carpenter glues (TB II, etc) will set in 30 – 60 minutes and can be unclamped and set aside. They still need several more hours to cure enough to be worked more. You can almost always go with the manufacturers suggestions.

-- Adversity doesn't build character...................it reveals it.

I leave it in the clamps for one reason in specific. Wood is going to absorb the glue making it swell a little. Then it will give off the moisture and shrink a little, hence the 24 hours. If you add to that any gap however slight that you have closed with the clamp, the pressure of the wood returning to the uncompressed shape will defineately pull apart your glue joint. So while several people will follow the no machine for 24 hour rule how would the natural wood stresses be different from machine stress? I will cheat with simple joints that are held with clamps purely for the reason that I do not have more than two hands or I need the clamp to push a tenon in but never on anything with the possiblity of spring tension like a glue soaked cutting board. Just my two cents, but I would be embarassed if I cheated on a cutting board charged 95 dollars for it and it fell apart in a seasonal change just because I needed to save clamp time.

Glue manufacturers put these clauses in for CYA purposes. Thru their testing they have determined that maximum strength has been achieved, under virtually all conditions of temperature and humidity, after 24 hours.

I clamp for 1 hour, remove clamps, scrape any squeeze-out off the wood (easier to do before it turns into concrete) and start machining in 2 hours. I’ve never had a problem. This has worked for me with Titebond yellow glue, Titebond melamine glue, polyurethane glue and Gorilla white glue.

The only glue I let sit overnight is plastic resin glue. I do all my clamping (vacuum bag or clamps) late in the day so it can sit overnight. Plastic resin glue is not one you want to rush.

-- Don, Diamond Lake Custom Woodworks - http://www.dlwoodworks.com - "If you make something idiot proof, all they do is make a better idiot"

It will certainly depend on your environmental conditions as well. Temperature and humidity are big factors, as is airflow. I have noticed this before on glueing up similar items. If the humidity is higher, or the temperature lower, it’ll take longer for the glue to set, and vice versa.

You either need to be patient and keep the clamps on for “just a little longer,” or get more clamps. I have never been in the situation where I’ve needed the clamps I just used right away.

I figure I can wait to use them because if I’m impatient, I try to think of the mess I’ll have on my hands if I rush the process. It’ll be 3-times the work compared to just waiting a little bit longer to be able to pull the clamps and use them on something else.

Maybe it is a good excuse to get a few more clamps? I’m not saying you need to go load up on clamps. I have slowly accumulated the number of clamps I have. I only purchase them on sale and in anticipation of an upcoming, or potential project, or if I’ve discovered that I’m sorely lacking in a certain size and kind.

I don’t know about the saying that “you can never have too many clamps,” but I’ve got several dozen, and I could certainly use more!

-- Jonathan, Denver, CO "Constructive criticism is welcome and valued as it gives me new perspectives and helps me to advance as a woodworker."

There is, of course, hide glue which sets in seconds and often requires no clamps at all. Since I’ve been using it I make far less use of my clamps and my pva glue bottle collects dust. It is well worth trying. If you don’t like it, you lose nothing. .......but you probably will like it.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

i once was in a rush for a last minute gift idea and i threw together a cutting board with strips of beech and cherry, the cherry was everything but dry, tree was cut just weeks before. and i used fast setting, not even watertight white glue. clamped 10 minutes and passed through the planer immediately after, routed the edges, sanded smooth and applied oil. the cutting board is used daily and it’s been almost two years and it holds up great. the cherry shrunk by almost 30% and you can see and feel the level difference but still it holds.

as far as clamping in “normal” situations goes, you should leave the clamps on as long as you can. it doesn’t hurt, but when time is an issue i use the minimal recommendation of 20 minutes on the pattex wood glue.

I’m a fan of leaving it till it’s cured.
I’m sure it doesn’t matter unless the wood was heavily sprung. I’m also not a fan of spring jointing.

-- When the moderator chooses sides, his site sucks.