You’ve likely heard the expression “belt and suspenders” and understand its meaning. Better to be safe, so to speak, don’t want your pants falling down at an inopportune moment.
That same discussion can be had about glue and screws. We don’t want that wood joint coming apart now, do we?
But seriously, the question of glue and screws is a legitimate one. Let’s examine it and see what we come up with for you.
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Wood Glue vs Screws
We’ve written in these pages in past posts about wood glue: the different types, the strength of glue, the right glue for the right project, and more. Here, here, and here, in case you want to brush up.
When the right glue is chosen, wood glue is stronger than screws. Screw strength is location-specific – its strength is limited to its location. Glue is strong over the entire wood surface of its application, whether gluing boards together to increase the thickness or applying it to joinery and joints. And, the greater the wood surface to which the glue can be applied, the greater the strength of the bond.
Is Wood Glue Strong Enough Without Screws?
Glue is actually stronger than wood. It is absorbed into the piece of wood and joins the strength of the wood to form stronger joinery. However, wood is not as strong as wood and glue together, and that’s why screws are also used. The glue would remain strong, but the wood itself would fail.
Screws add that extra bit of strength between the materials being joined, especially with some types of joints. Glue alone would not be sufficient with a butt joint, mainly because of the smaller surface available for the adhesive.
However, when there is a large surface area to be joined, wood glue can be sufficient without the use of screws added. Consider the surface areas when you are joining two pieces of 1 x 10 lumber to increase thickness for a tabletop, as an example. There’s plenty of surface area for glue application, and the bond will be strong.
Consider, also, a box joint suitable for joining solid wood panels. The “fingers” of a box joint increase substantially the surface area where glue can be applied, and a very strong joint is created. Again, it is the surface area that matters. Screws are not necessary and do not fit in a box joint.
Should I use Wood Glue and Screws Together?
You’re probably starting to see the picture emerge as to the relationship between glue and screws. Lots of surface area? Glue is likely enough. Have a joint that must support a good deal of weight? Glue and screws are necessary.
Pocket hole joints, though, don’t necessarily require glue. In this instance, screws are likely sufficient. However, that is not to say glue wouldn’t help. Pocket holes make a strong joint, but it’s wood you’re working with, and you have to take its strength, or lack thereof, into account. We’re already noted that glue is stronger than wood, so gluing a pocket hole joint merely enhances the strength of the joint.
Belt and suspenders, glue and screws. It’s the same thing.
Can You Glue Screws To Wood?
The simple answer is yes, you can. Should you, though? Metal screws won’t absorb the glue, though, as wood will. It’s that absorption of glue by wood that gives the bond its strength, a strength greater than the wood. But, it won’t hurt to use glue in the screw holes.
However, don’t use epoxy with screws if you think you will ever need to remove the screws in the future. Epoxies are stronger than glue, and the screw will be very tightly held in place. You can heat the screw to help with its removal, but more than likely, you’ll end up having to cut and drill it out.
Is Liquid Nails Better Than Wood Glue?
This is an excellent question, and the answer depends on the project and the surfaces being joined.
Liquid Nails comes in a wide variety of types that fit the use of virtually any type of material being joined, from wood to metals, ceramics, glass, and even leather. It is formulated for construction, so its adhesive qualities and bonding strength are stronger than wood glue.
It’s especially good to use with non-porous surfaces, such as painted or varnished surfaces. It’s a good choice, too, when clamping pieces together isn’t possible or practical because it has a much faster bonding and drying time than glue.
For a quick application that needs little if any drying time, Liquid Nails is a good choice. However, in a wood-to-wood application, wood glue is considered to be the better choice. This has to do with absorption: wood glue is absorbed by the wood and thus creates a strong bond; Liquid Nails is not, and therefore is the right choice for non-porous surfaces.
The curing time between the two is approximately the same. Latex varieties of Liquid Nails can take up to a week to cure, and so can wood glue.
If your project has a combination of porous wood and non-porous materials (glass, ceramics, vinyl, leather, and, yes, nonporous wood), you will likely want to use both Liquid Nails and wood glue. But, if your project is simply a porous wood, glue is the better option.
Porous refers to pores; a porous wood has pores and vessels on its surface and will absorb wet substances. A nonporous wood has no pores or vessels on its surface and does not absorb wet substances well. Hardwoods are porous; softwoods are nonporous.
We keep repeating ourselves in our posts, but it is worth saying again: the right tool for the right job. Glue has its place, and frankly, it’s most places for most wood projects. However, screws become necessary for the strong bond your project needs when the surface area isn’t large.
And as for Liquid Nails, it has its place and its use in your woodworking shop. Always have wood glue on hand; always have screws on hand; and maybe sometimes, have Liquid Nails handy, too.