Braz, If you tell me where to place the post (or if you want to create one) this information can be placed there. As time progresses, I'll add more things that will be beneficial. Like the following:
Working in the Wood Products industry as a "Glueman" I always got the call when there was a problem. It usually started out with the phone ringing, and before a hello could even be uttered, a booming voice would declare. "Your glues no damned good! Everything is falling apart!" Well after listening to a description of the problem. I would start asking some questions with the intention of getting to the root of the problem. Ex. Caller claims that his edge glued panels are all falling apart. I would ask if they were completely falling apart? Or if perhaps a crack was appearing on a single glueline? I would then calmly explain that the glue is not going to be biased and bond one board, but not the other.. Something has to be going on? Here I would be informed that perhaps they were a little hasty in their initial description of the problem. Some of the questions I would then ask would be as follows:
*What is the end product being produced? (Panels, squares, frames, etc.)
* What species was being used?
*What type of joinery is being used?
* What type of gluing equipment is being used? Ex.Clamp carrier (A ferris wheel of clamps), Radio Frequency Gluing machine, Hot Press, Cold Press, framing clamps, etc.
*What is the moisture content of the stock? Has it been equalized and conditioned? -Is it stress free (no casehardening stresses)?
*Are they drying their own lumber? Or buying it from a supplier?
*How are the joints prepared? Straightline rip saw, Gang rip, molder, knife planer, abrasive planer, Double end Tenoner, Mortising machine, shaper, Finger jointer?
*How is the adhesive being applied? Glue spreader, squeeze bottle, roller, etc.
*How much clamping force is being applied?
*Placement of the clamps, and number of clamps being used?
*How much assembly time is required? -From the time the adhesive is applied, to the time it undergoes full clamping pressure?
*How long is the adhesive allowed to cure? -Clamping time?
*What are the Plant conditions? Temperature, Relative Humidity?
I typically knew what adhesive product they were using. Sometimes however, a salesman would have them using a particular product for one reason or another? (speed of set, cost, color, odor, etc.) Here this product may not have been ideally suited for the application. All adhesive have a "range" in which they work best. Some adhesives have a much bigger range, and are more forgiving. Others have a much smaller working range. These require a more precise balancing act for them to perform optimally. I'd later check with the salesman to get his input. After which I would explain my take on the problem to him, and discuss my findings.
I could usually solve the problem over the phone, but would schedule an immediate trip to the plant in person. Usually by the time I arrived the problem had been detected as one of the above mentioned areas. I would then walk the plant people through the preventative steps to insure that the problem would not occur again.
Some things for Call makers:
Anytime you can build strength of design into your product you will be ahead of the game. Ex. Using mortise and tenon joinery to assemble multiple pieces in a call, verses a butt joint. In this example, the mortise would consist of a round hole bored on a drill press, or lathe. The tenon would be turned on the lathe. It is all about maximizing gluing surface area. Some important factors to consider are the following:
*Diameter of the tenon. - Ex. A 7/8" diameter tenon has more surface area than a 3/4" tenon of the same length. Anytime you can use a bigger diameter tenon, the stronger the joint will be. -Provided you do not sacrifice the "sidewall" thickness of the mortise. If the stock, and design of your call allows it, then try and use as large a diameter tenon as possible.
*Length of tenon. - In testing done in the furniture industries and Universities, it was determined that the longer the tenon, the stronger the joint. -Once again, provided the design allows for it. A length ratio of 8:1 (eight times the diameter of the dowel/tenon) Ex. A 1/2"diameter dowel, should be 4" in length (8 x 1/2 =4) to achieve its ultimate strength. Coupled with utilizing the maximum allowable dowel diameter..A very strong joint could be design.
Now granted, a game call undoubtedly cannot be asked to utilize dowels and tenons of the proportions described above. -But the point that needs to be recognized is; "Try and utilize the maximum diameter, and length that you see fit, and your particular call will allow."
Mortise/Tenon Tolerances:
Using our above example of a drill press bored hole, and a lathe turned tenon for a call. The dry fit of the pieces should be "snug", and able to be assembled (without adhesive) with some mild resistance. If you have to pound the pieces together, you are building in a plane of failure by causing "permanent deformation" or crushing of the cell wall material of the wood. Remember, a water based adhesive will cause some softening, and swelling of the surrounding fibers in the joint. On an excessively tight joint, this will be a detriment. Here the softened fibers will crush and deform. The adhesive will also be scraped to the bottom of the hole. Where it may cause "hydraulicing" of the pieces. The snug, proper fitting joint will allow the adhesive to be pressed into a thin film between the mortise and tenon. Clamping pressure will then hold the pieces together until the adhesive cures.
On the opposite side of the spectrum is a poor, loosely fitting joint. When this type of joint is used, only a poor bond can be expected. If a water based (wood worker glue, Titebond, etc) or a Urethane glue is used. The glue joint will exhibit "puddling" of the dried adhesive. -This means that the glue will pool and dry in the voids and gaps. Resulting in a thick, weak glue joint. That foaming Urethane glue is not going to do a bit of good! In this joint scenario, the only adhesive recommended would be an Epoxy. Epoxies are gap filling, and will bridge a small gap sufficiently. The thing to remember about Epoxies is that the slower setting ones are the strongest. So by using a 2hour cure time epoxy, verses a 5 minute cure epoxy, your joint will be that much stronger.
Another very important thing to remember is the placement, and spreading of the adhesive. Do not squirt it onto the bottom of the hole, and expect it to squeeze upwards when clamping force is applied. The glue needs to be applied to the sides of the hole (mortise). In addition, applying it all around the tenon will further guarantee success.
One thing that I do in the construction of this type of joinery is to cut a few small channels around the sides of the tenon. And also around the inside of the mortise (if the design, and wall thickness allow it). Coupled with an epoxy resin, this joint will last the ages. The jury is still out on using grooves with Water based adhesives. Ex. straight grooved dowels, verses spiral grooved dowels. In my opinion, a small groove, or series of shallow grooves cannot do much damage, and will probably not affect the joint one way or another when using a Water based glue, or Urethane glue for that matter.
So for now this will provide you all some insight. If you have an interest in learning about some of the other above mentioned problem areas, just let me know? I'll try and address them in an ongoing fashion. Thanks for reading along and bearing with me.
Dave
