Coarse Thread Screws for Joinery

They might hold, but will they stand the test of time? Professionals weigh in. August 30, 2005

Does anyone have experience using coarse thread screws in place of dowels or mortise and tenon joinery? Will they yield a structurally sound joint?

Forum Responses
(Furniture Making Forum)
It depends on what you're joining together. Lots of companies use coarse threaded screws to hold butt joints together on cheaper stuff. Will it last over time? Probably not, but it's fast and cheap and easy for low paid, unskilled employees to do.

Quality joinery usually requires that you do the work and learn the skills to perform proper joinery techniques. Antiques were made with mortise and tenon joints, bridle joints, dovetails, and other joinery work. These pieces are still around today because the workmanship was sufficient to stand the test of time. A screw may not be good enough to match that, unless you're building an outdoor deck.

From the original questioner:
The technique I'd like to use is similar in spirit to the way Maloof joined legs to his seats - by creating a rabbet and reinforcing it with coarse screws, then plugging them.

Take a more proactive approach. Make a bunch of different joints and see what kind of abuse it takes to break them. I'm sure the makers of old would have used pocket screws or biscuits if they were available at the time.

I agree. If I have a joint in question, I make up several samples, and test them to destruction. I can usually tell by muscle. But a more scientific approach would be to use a spring scale or known weights, short of going to a testing lab.

Coarse thread screws with a properly sized pilot hole are pretty strong. So are dowels, dovetails, mortise and tenons, etc. It just depends on your particular application, how strong it really needs to be, and how much time you want to spend on it.

From the original questioner:
Thank you for your responses. I have made some test joints - one using a rabbet reinforced with screws and the other a mortise and tenon. They seem to perform equally well. Of course, I don't know how they'll last over a span of 50 years.

Wood shrinks and will (or may) loosen the tightest screw joint. Commercially made cheap chairs are one prime example. Kreig type joints are fine for temporary (10 years) construction, but if you want the piece to last, learn how to mortise and tennon. It really is not that hard.

I agree with the rest of the posts. Screwed joinery will not stand the test of time. I spent many years in the residential and commercial mass production cabinet field and these joints do not last. I agree also that the mortise and tennon is not a very hard machine and surprisingly, with the correct jigs and equipment, does not take too terribly long to make. I figure when in doubt, use what has worked for centuries.