What is a Drawbored joint?

What is a Drawbored joint?

What is drawboring? It’s a technique that greatly strengthens a mortise-and-tenon joint, transforming it from a joint that relies on glue adhesion into a joint that has a permanent and mechanical interlock. In essence, you bore a hole through both walls of your mortise.

How do you repair a mortise and tenon joint?

To repair a loose mortise and tenon joint, it is best if you can completely separate the two pieces. Try and pull them apart with your hands, or use a small rubber mallet to gently knock them apart. Use a scraper or light sandpaper to remove all of the old glue from both the mortise and the tenon.

What tools should be used to remove a mortise?

Chisels. No matter how you cut a mortise, you’ll need chisels to smooth and square its walls and corners. Start with a chisel as wide (or nearly as wide) as the mortise ends and use it to square both ends of the hole. Then, clean up the side walls with the widest chisel that fits into the mortise.

What is draw boring?

Draw boring is a technique that strengthens a mortise and tenon joint by using a dowel and offset holes in the mortise and tenon to draw the joint together. This combines the chemical strength of glue with mechanical strength of an interlocking dowel.

What is a Drawbore pin used for?

The traditional solution is using drawbore pins. Drawbore pins not only let you assemble the joint but they have an eccentricity that allows you to tighten up the joint without banging down. It’s a technique that is still used today to align steel beams for assembly.

How do you loosen old glue joints?

Use acetone or denatured alcohol if you suspect the joint was glued with epoxy or urethane.

1. Drill evenly spaced holes into the joint with a 1/8-inch or smaller drill bit.
2. Fill a syringe with warm water, white vinegar, acetone or denatured alcohol, depending on the type of glue you are trying to soften.

How is a drawbored mortise and tenon joint different?

A drawbored mortise & tenon joint is similar to the pegged version, only the hole in the tenon is slightly offset so that when the peg is driven home, it pulls the tenon further into the mortise. Most of the time, a joint with this much mechanical strength really doesn’t even require glue!

Where to mark the offset on mortise and tenon?

Disassemble the joint and for better visibility, use a pencil to darken the marks in the cheek of the tenon. Measure and mark the offset (the offset should be located closer to the shoulder of the tenon). How much offset depends on the wood and the application.

What to do if glue fails on mortise and tenon chair?

One option is to simply reinforce with pegs. While this doesn’t really make the joint all that much stronger, it does help hold the parts together in the event of glue failure. I have repaired numerous chairs where the only thing preventing the piece from catastrophic joint failure was a small 1/4″ dowel driven through a key tenon.

How do you drill a hole in a mortise?

Drill two holes through the mortise piece, making sure you go deep enough to penetrate the material on the other side of the mortise. Dry assemble the joint and use a brad point bit to locate and transfer the hole centers in the tenon. Disassemble the joint and for better visibility, use a pencil to darken the marks in the cheek of the tenon.