I'm looking for a better glue system, other than Titebond. Iíd like something that is easy to use, not too expensive, with long enough open time to glue up casework, but is fast setting. Does PUR glue need clamping? Is the open time long enough to clamp if you need to?
From Jeff Pitcher, forum technical advisor:
There are actually two different PURs available for use in most shops. One is a liquid PUR such as Gorilla Glue or Excel. The other is a PUR Hot Melt available from a number of companies.
Generally, Titebond is preferable to liquid PUR unless you need something waterproof or you are gluing things other than wood. For most applications Titebond is more than adequate and significantly less expensive than liquid PUR. Both must be clamped, both have about the same open time but Liquid PUR is 3-4 times the price and doesn't clean up well.
Hot melt PUR might be a good alternative if you can justify it in terms of increased production and decreased labor cost. If you can't see real savings in these areas you'll be spending five times the money on adhesive with no real increase in bond quality.
Joints were dado, biscuits, and screws using Titebond, versus a set of joints that were simple butt joints glued with PL premium, and a set of butt joints with PL and a 3/4" x 3/4" cleat glued and pinned on (no clamps) for added glue surface area.
The results were as follows:
Melamine: The screw joints broke at around 30 lbs, same with the biscuits. The dados went to 37 lbs. Dados are far weaker than people think due to the fact that the cutting of the groove destroys the integrity of panel.
PL broke at around 45 lbs, ripping out the HDPB core, but no joint failure.
Hereís the real discovery:
The joint with the PL and glue cleat broke at 127 lbs!
Essentially the same results with the pressure tests on the plywood.
My whole cabinet business was revolutionized, and all my case joinery utilizes PL premium butt joints and two "locator" nails to keep the joint from slipping during cure. I put a couple deep-throat clamps in the middle to aid in pressure till set. Itís hard to measure, but I figure I saved about 10 - 15% overall time by eliminating the time consuming joint cutting operations like insertion dowel, dado, etc.
For face frames I use PL all the way. I would use Titebond only for solid wood-to-solid wood.