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Thread: Any validity to this glue-up advice?

  1. #16
    Glue joints can certainly be starved when using PVA and other glues. And this is using woodworking clamps. I have done it, not for a lack of glue mind you, but for an excess of pressure. I would noe subscribe to the technique described for the application specified. Nor would I use PVA. Plastic resin glue. Look it up. Precatalyzed and then powdered is plenty fine. PVA is a lazy man's glue and for a good reason - it is effective in many applications. In your application you can do a lot better than PVA for not much if any more money.

    I have glued many species of exotics. Not once have I "removed oils" with acetone or whatever. Not once has a joint failed. Cocobolo, Brazilian rosewood, purpleheart, teak, whatever.

    With experience you will know when a joint is clamped up properly. If you are exerting might beyond one handed tightening you are trying too hard.

  2. #17
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    I did some additional research and found this advice regarding end grain joints on the Titebond website:

    Get good results gluing end grain joints.

    Although good joint design minimizes the need for gluing end grain, sometimes end grain joints are unavoidable. The strength of end grain joints can be improved if the "open" end grain is first sized. A sizing mixture may be made by mixing one part to two parts water to one part glue. Place the sizing mixture on the end grain. Let it soak in for no more than two minutes, and then continue with a regular application of glue.
    Lee Schierer
    USNA '71
    Go Navy!

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  3. #18
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    I have been under the impression that the primer coat layer was something done with hide glue. I've never done it with PVA.
    Bumbling forward into the unknown.

  4. #19
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    Thanks for all the replies. I did a little googling on this topic and found that Titebond recommends that, as mentioned above, end grain joints be sized first with watered-down glue. I did not find any recommendations to size long grain joints from reliable sources.

    As for clamping pressure, most advice I found seemed to indicate that it would be difficult to starve a glue joint using pressure, especially in hardwood, using typical woodworking clamps. Most sources seemed to say that you need quite a bit of pressure to get a good joint. A FWW article from 2010, for example, says that a 36" x 3/4" long grain to long grain joint in maple would require over 12,000 pounds of pressure (about a dozen pipe clamps) to achieve the best joint. They arrive at this figure by multiplying the 27 square inches of glue surface by their recommendation of 450 psi for maple.

    On the other hand, Titebond seems to say in this video that you don't need that much clamping pressure. In Titebond's technical guide for glue application, they recommend 200-300 psi for the hardest hardwoods. This would still require 8 pipe clamps for FWW's sample joint. Confusingly, they recommend placing clamps every 8-12", which would only give room for 3-4 pipe clamps on FWW's sample joint. Even for softwoods, this doesn't seem like it would allow for enough clamps on a typical 3/4" board.

    Many sources reference Bruce Hoadley's Understanding Wood, which I don't own. If anyone has this book and would like to check out what he says on this topic, that would be appreciated.

    I appreciate the recommendations for other adhesives but, for this beginner project, I will stick with the PVA I already have.

    Matt, that is a beautiful bow. I've been finding out that bow-making is quite the rabbit hole, with a tremendous amount of technical knowledge involved, especially about the characteristics of various woods. If my son stays interested I may dive in a bit.

    Happy Sunday to all.
    Last edited by Brian W Evans; 05-07-2017 at 8:52 AM. Reason: Fixed one of the links.

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