Blog: My Thoughts On… By: John Heisz
Here are some of the things that I’ve learned and work by.
I use them, I like them. Screws, nails, bolts – all good. Don’t be afraid to use them in the appropriate place but don’t overuse them – if one nail holds and two nails hold better, that doesn’t necessarily mean thirty hold best. Knowing what fastener to use and how many is knowledge worth acquiring.
For some, it’s a mark of quality if something is put together without mechanical fasteners; for me, it’s not about what you think you should waste your time doing, as long as the finished product is just as well made. “Well made” in my book, means the judicious use of fasteners to speed the work and improve the results. If the results look the same, perform the same and prove to be just as durable over time, that is what matters.
Glue is much better today than it used to be. For general woodworking, nothing more than regular white PVA glue is needed to make strong joints. More often used is yellow carpenter’s glue, which has aliphatic resin added. This is actually not significantly stronger than white PVA glue but has better initial grab, dries a bit harder and is more moisture resistant. Both of these glues need tight fitting joints to be effective and both suffer from ‘cold creep’ (the joint will move when subjected to a load. If you believe that empty box you built has no load, you are forgetting woods seasonal expansion / contraction cycles).
More and more, I’ve been using polyurethane construction adhesive to assemble my projects. Though this is not as strong as carpenter’s glue, it is certainly strong enough. It has several advantages as well:
- Longer open time gives ample opportunity to position parts.
- Waterproof, creep proof joints.
- Excellent gap filling properties.
- Low cost and long shelf life.
- Adheres to other materials, such as metal or finished wood.
- Easy to remove squeeze out (unlike liquid polyurethane glue, it doesn’t foam)
- Drip proof.
- Seems to be more shock resistant than wood glue.
There are disadvantages:
- Comes in a cartridge, for use in a caulking gun.
- Pretty much the only way to get it off your skin after it has dried is to wear it off. This can take days…
- You’re not going to wash it out of your clothes – forget about it.
There may be more of either – these are just my observations so far. For me, the advantages vastly outweigh the disadvantages.
All of our modern joinery was developed long ago, mainly to cope with the fact that our ancestors didn’t have high quality fasteners or super strong glue. To hold it together in days of yore, you would need to devise a method of joining the pieces so that they wouldn’t easily come apart.
Today, we really don’t need these kinds of joints, since we have those high quality fasteners and super strong glue at our disposal. I’d hazard a guess and say that very few of the traditional joints for woodworking would even exist today if these materials were available to those ancient wrights and carpenters. Time is money, and always has been – those joints were not developed out of a sense of quality, but as a necessity, and the employers of the day would be all over doing something in less time with more predictable results.
Today, it’s about appearances. If that drawer is not put together with dovetails, it’s obviously not well made. Never mind that it may never fail, or that the joint may be just as strong as the prettier one.
Some myths: “Too much glue makes the joint weak” – extra glue will squeeze out of the joint under clamping pressure, so it’s irrelevant if you put too much on to begin with. Putting too little, on the other hand, does make for a weak joint.
“You can squeeze all of the glue out of the joint if you clamp too tightly” – it’s virtually impossible to put enough pressure with regular hand operated clamps to do this. Clamping pressure needs to be high, as it will actually force the glue deeper into the wood fibers to create a stronger joint. Use strong clamps (those ‘quick grip’ type clamps don’t exert enough force to seriously clamp something for gluing) and lots of them.
Making something strong enough for the purpose it will serve is economy of effort and material. To over-build has become noble, for some reason. I prefer to keep the end use in perspective and make it only as strong as it needs to be. For me, this is noble.
As mentioned above, I use a glue that I know is weaker but this difference is marginal, and will not be a factor in the things I build. There is the tenancy to buy into the marketing hype from the manufacturers but the bottom line is that the differences between different formulations is irrelevant for the bulk of woodworking tasks. Use the one you like, has the nicest looking bottle, or is cheapest.