Clamping time

[Bigdog72]

This is a general question regarding how long one should keep a glue up in the clamps. I know that type of wood, ambient temperature, type of glue and about a thousand other things factor in. What I am looking for is a general rule of thumb for "cooking time" to coin a phrase from Norm. My reason for asking is my shop is only heated while I am in there working. I want to be able to bring my glue ups to the house without having to carry the clamps. Not lazy, just don't want to scratch up the walls with unwieldy clamp bars.

Thanks in advance for your comments.

 

[FredP]

I generally wait about an hour in the clamps. after that it depends on what I need to do to the board. Just moving around it is usually fine. planer? I wait a while longer. I use tightbond11 for everything. if I use klingspore glue or elmers I leave clamped twice as long or more. mid summer I find most of the time 20 min is enough for light work. winter I usually leave clamped over night. unless it is nearly freezing or colder taking it inside is a good plan. you don't want the glue to freeze before it is set.
YMMV....:gar-Bi

 

[bobby g]

Geoff,

Take a look at the time stated on the glue bottle. That should work fine for the purpose that you described.

bobby g

 

[FredP]

Geoff,

Take a look at the time stated on the glue bottle. That should work fine for the purpose that you described.

bobby g

yehbut... that requires reading directions. we are men!:rotflm: directions go strait to the trash can.:gar-La;
A good indicator is the squeez out. is it wet? rubbery? or rock hard? wet means leave it in the clamps. rubbery means you can remove the clamps but be careful with the handling. It is always better to wait untill it is fully cured if possible.:icon_thum

 

[junquecol]

I agree with Bobby G, read the directions. Remember that items being clamped have to be at proper temperature, not just air temp. in the shop.

 

[Gofor]

Like Fred, for me squeeze out is the key. If its hard/tough, I will move it if its not too large.

TB II or III, 15 minutes in 90 degree summer heat is usually enough in the clamps but give it a bit longer. This time of year I try to give it 30 min to 1 hr. Also depends somewhat on how large the piece is and the stress on the joint. For a book-matched cabinet panel, cabinet door, the above applies (I'm scraping glue off at 30 and sanding/moving at 45 min.) For a bookcase, heavy chest, etc, I go for several hours which usually means overnight before moving. TB III does take a bit longer in the winter, but have seen little difference above 80 degrees.

My garage usually stays about 10 to 20 degrees above outside temps in the winter, but rarely drops below 55 due to a freezer in it that pumps out some heat. I have never had any problems with the glue failing to cure up left in place overnight.

Go

 

[red]

, for me squeeze out is the key. If its hard/tough, I will move it if its not too large.

+1

Red

 

[ehpoole]

For minimum clamping times with Yellow (PVA) or Polyurethane glues of normal working time (not extended working time formulations) my minimum schedule goes something like the following:

- Minimal weight and minimal stress (especially if also pinned): 30-45 minutes

- Of moderate weight or stress: 1 hour to 1 1/2 hours.

- Of heavy weight or subject to significant stress: 4 hours

If I am using an extended time glue, I would add an additional 30 minutes to each.

However, these are my minimum clamping times. If I were going to move the item and I was going to have to place any stress on these glue joints in the course of moving them, then I would prefer to wait a minimum of 2 hours before I moved the item. On the other hand, if the item lends itself to being moved without placing stress on the glue joints, then I would feel safe moving it after an hour or so.

I'm more lenient with the times when the glue is supplemental (e.g. screw or nail fasteners have also been used) -- in that case the joint isn't 100% dependent on the glue and the fasteners will both help to keep the joint tight and the parts from slipping. If the glue is supplemental, an hour is probably a safe bet unless you'll be placing lots of stress on the joint.

 

[bigcat4t9r]

Just to add in building my workbench base w/SYP - TBII says 4 hours due to resin content. I suspect that would apply to other similar woods.

 

[Howard Acheson]

First, start with what it says on the adhesive you are using. PVA type adhesives have a much shorter clamp time than Urea Formaldehyde or rescorcinal.

Understand that the clamp time is very dependent on temperature. The label time is based on 70-75 degrees and 50% Relative Humidity. The clamp time about doubles for temperatures between 60-65 degrees and may even never properly dry at temperatures below 55 degrees. UF adhesives will not work at all in temperature much below 70 degrees. The temperature for the board, adhesive and the ambient temperature must be maintained for the whole drying time.

An old electric blanket is an excellent way to keep a glue-up warm in colder weather.

 

[Bigdog72]

An old electric blanket is an excellent way to keep a glue-up warm in colder weather.

Great tip!! Never would have thought of it!!

 

[ehpoole]

Understand that the clamp time is very dependent on temperature. The label time is based on 70-75 degrees and 50% Relative Humidity. The clamp time about doubles for temperatures between 60-65 degrees and may even never properly dry at temperatures below 55 degrees. UF adhesives will not work at all in temperature much below 70 degrees. The temperature for the board, adhesive and the ambient temperature must be maintained for the whole drying time.

That's a very good point, which I forgot to mention. During glue-ups (and for a few hours before to at least 12 hours after) my shop is maintained at a temperature between 67-72F and a humidity of 30% (winter) to 50% (summer). As such, all my times are based upon experience at those temperatures.

Most glues want temperatures of at least 60F, with a range of 70-80F often being more ideal. In the 50s things get much more sketchy, much over 90F and it depends heavily upon the glue. At high humidity, water based glues like PVA have a much more dificult time setting, though water activated glues, like Polyurethane, should do just fine. Epoxy is an exothermic chemical reaction, so as long as you are within the acceptable temperature range, humidity should not matter since it is neither water-based nor water-activated.

With respect to SYP, the few SYP projects I have done I have found my schedule to work just fine without modification. Though I'm sure that there are probably more resinous SYP planks out there than those I've worked with. Then again, I'm known to cheat and add a pin or two here and there.