Clamping pressure??????

[Jim Colombo]

Assuming using a yellow glue on hardwood segments:

What is the correct amount of pressure to put on rings during glue up of the stack?
AND
How long does this pressure need to be held?

[Brian Kent]

A test in the last year or so basically said that you can't over-clamp. I would see more of a limit on causing slippage but otherwise I don't imagine an over-clamping problem. Even though it says to clamp for 45 minutes and don't stress for 24 hours, I usually keep it in there at least over night. I like hard woods, and some, like cocobolo, is hard to clamp. After 45 minutes the glue is still wet inside because of the dense, oily wood.

[Bill Bulloch]

A five inch rubber band that is a half inch wide has about 9 - 10 lbs of pressure when new and that seems to work. As for glue time, I will let my glued segments sit for 30 minutes or more before flatening the ring with the drum sander. I glue my rings up on the lathe and let them sit under pressure for about 15 - 20 minutes before gluing the next ring.

[Aric Krueger]

Check this useful information from tite bond:
http://www.titebond.com/news_article/12-01-24/Video_Spotlight_Gluing_Tip_of_the_Month.aspx

I usually clamp pretty tight but not "crushing" force. I make sure the wood's moisture content has stabilized in the house before I start gluing.

I also have learned to leave the glue-up in the house for about a month after I've removed the clamps (depending on the size of what I've glued-up, even longer) before I put it to the lathe. The reason being that the glue actually can add enough moisture to the wood that it swells slightly. Sometime after the turning is completed, when the wood looses the moisture, all the glue lines can be felt. :mad: ...aggravating.

[Michelle Rich]

some folks use the rub method and no clamps at all..no matter what way you use, the segments must be perfect before gluing (close up perfectly when no glue) and let the ring dry.

[Steve Peterson]

There was a thread on one of the forums recently about the proper clamp strength. The absolute maximum clamp strength occurs with 150 to 1200 psi or more of clamping pressure depending on species and flat sawn vs quarter sawn. However the strength does not reduce much with lower pressure. You get around 60-70% of the maximum glue strength with no clamp pressure and the glue joint will still be stronger than the wood.

Steve

[Justin Stephen]

I use a homemade clamping table with a screw press. The rings being clamped rest on a neoprene pad on top of the firm clamping table surface. I bring the screw press down to where it is firmly against the work being pressed and then add maybe a quarter or third of a turn on top of that. I haven't found the need to tighten things anymore than that and, in my experience, tightening more than that causes the rings to want to slip n' slide a lot of try and wander off center too much anyway (I don't use anything to hold them centered). It really doesn't take very much.

I leave the glued rings under clamp pressure for about 20 minutes (I set an egg timer) before I release the press and add the next ring. Once the entire glue-up is done, it sits in the house (usually still in the press) for at least 24 hours before it goes on the lathe. I do all of my gluing and what not inside the house.