Pros discuss the relative merits of various glues in cabinetmaking and woodworking applications. October 20,
Question
I'm looking for a better glue system, other than Titebond. I&#;d 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?
Forum Responses
(Adhesives Forum)
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.
About fifteen years ago, when PL Premium polyurethane construction adhesive was introduced, I discovered that PL pretty much welds to melamine as well as any other porous joint, such as plywood edges to solid wood, covering most case joinery.I embarked on a test. I made a bunch of 4" x 4" x 4" L-shaped sample joints in melamine and birch ply, to test in an arbor press with a weight scale to record the threshold weight the joint would hold at the point of breaking.
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.
Here&#;s 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.
Conclusion:
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. It&#;s 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.
We recently had a Jet-Weld gun in our shop for a week or so. It is a PUR hot melt system. I was interested in using it to bond mitered moldings, including crown moldings. After some testing we found we could get a perfect crown molding joint bonded with a 90 degree corner. We made a simple fixture that gave us a 90 degree corner to work from. We then glued one surface, rubbed the two corners together to spread the glue and held in position for 15 second. In five minutes you could sand and you could handle the parts in 20 minutes. It was very strong. The down side was that the tube could only stand being heated for 16 hours before it would have to be discarded, and it was expensive. For our purposes we did not have the need for the added speed. I could see the value in the future to increase flow and reduce labor. If I was installing in the field I would get a Jet-Weld gun or one of the smaller Franklin systems. The speed and strength is amazing and you could eliminate many, if not all pins. You would add about $20 an install in material.I got the local 3M rep to loan us the gun.For tricky casework PL Premium is the only way to go. It actually lubricates tight joints so they fit well without grabbing. I'm starting to use it for tabletop edge-to-edge laminations simply because it can be sanded and the glue line looks and stains like wood. Fewer clamps are needed too.I'd like to try the PL but where do I get some PL Premium to try? Is it the same "PL" line of adhesives I see at Home Depot? With the short shelf life of PUR glue, I don't think it would work here.All the big hardware stores carry it. I buy the big tubes.
Last Updated: July 1,
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When we first get into woodworking most of us are surprised to learn that glue makes the world go &#;round. We conjure up an image of a flannel-clad, burly man sawing tree trunks and hammering nails.
But no, not all woodworkers are burly men and we don&#;t use nails so much anymore. But glue&#;.that&#;s what we buy in bulk. I use gallons and gallons of glue every year.
Since glue is such an important part of woodworking, here are 7 things every new woodworker (every woodworker, for that matter) should know about glue.
There are a couple of options when it comes to temporarily attaching two pieces. One is double-sided tape, and while this is the strongest method, it is much more messy and intensive. Good double-sided tape is really tough to get loose and clean up. I still use when I need ultra strong temporary adhesion, but otherwise I use&#;.
Blue tape and CA glue are wonderful materials for temporarily joining two surfaces. It can be used to attach router templates for patterns. I like to use it to attach a piece of sandpaper to a flat surface (usually my table saw) and use it to sand boxes. You can also attach a strip of sandpaper to a block of wood to create a sanding block.
It&#;s really a simple technique. A piece of masking or painter&#;s tape is put on each surface, spread a bead of CA glue on one side, and then attach.
I extend the tape beyond the edges to make it easy to align once I flip it over. Otherwise, you won&#;t be able to see where the tape is on the underside of the piece.
This technique is so effective that I can create my favorite blue-tape-and-CA-glue masterpiece&#;DOUBLE DRILL! (watch the video to really experience Double Drill).
It&#;s also strong enough to create an impromptu tool rack. (Note: this is a joke&#;don&#;t attach things to the ceiling&#;they could fall on you).
Joking aside, these silly shenanigans show how strong CA glue and blue tape can be.
If were to look at the end of a piece of wood under a microscope, you would see that they look like a group of straws or a broom. From the end you can see many more gaps than if you look at it from the side.
When you put two pieces of wood together with the end grain of one to the side grain of the other, glue soaks into the gaps of the end grain and starves the joint for glue. To fix this, pack some glue into the end grain and let it dry for about 10-15 minutes. Then, apply more glue and it will sit on top of the partially dried glue that&#;s acting as a seal of sorts.
This will keep more glue at the joint and make for a much better bond.
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Glue acts as a bridge, of sorts, that binds to pieces together. The closer you can get the pieces to each other the shorter distance the glue has to bridge and the stronger the joint.
Clamps pull the pieces together and hold them tightly in place while the glue dries. You can also use screws or nails to hold the joint together, but they aren&#;t quite as effective as a traditional clamp.
If you aren&#;t able to get clamps in an area, but still need to securely attach two pieces of wood, you can use CA glue to quickly dry and hold the pieces while the wood glue dries.
Make sure there is glue on the very ends, but just inside of that leave a gap and then a couple of other gaps in the middle at equal increments. Add CA glue in the open gaps, put the wood in place, and hold for about 30 minutes.
Whentwo pieces are clamped properly there will be glue squeeze-out. Since glue does not stain and finish the same as wood fibers the squeeze-out must be cleaned completely.
One way to clean up the glue is to use a wet rag to immediately wipe away as much glue as you can. The problem with this method is that you risk diluting the glue and causing it soak into the wood. Woods like oak with deep open grain are specifically susceptible to this.
The other method is to wait about 30 minutes and then scrape it away.
Before adding any stain or finish use a wet rag to check for glue remnants. If you find any or if you start to apply stain and catch some glue spots, sand until you remove the glue and apply finish.
The style of wooden and DIY furniture today includes a lot of cracks and knots. If you&#;re going for this look, you still need to secure those imperfections or they&#;ll just keep opening up over time.
I used to use epoxy tinted with wood shavings, if need be, but that can be messy and more consuming. Now, I&#;m using this tinted CA glue from Starbond. It&#;s simple and easy to just go straight from the bottle and fill the cracks and knots.
For lighter woods or to leave more of a reveal in darker woods, I will use clear CA glue.
Wood glues are made with specific characteristics. The red Titebond, for example, isn&#;t waterproof or water resistant and has a fairly short assembly time. Assembly time is the amount of time you have before the glue starts to dry.
The Titebond Extend has a really long assembly time for those projects that are complex glue-ups. But, if you don&#;t need a really long assembly time and your project is not going to be outside, buy the cheaper non-waterproof glue&#;it can be about 30% cheaper.
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