Repairing Small Cracks in Projects
It’s inevitable. No matter how careful you are fitting your joinery, doing dry assemblies to check fit, and rehearsing your assembly process to make sure you have everything in place and ready to go, Murphy is going to show up from time to time and throw a little hiccup into things. So it was as I was assembling the arm and spindles to the seat of a chair that I recently completed. I had the spindles inserted into the arm and had done multiple dry assemblies during the construction, so I was sure that things were ready for assembly. I added glue to the seat mortises and started to fit everything up and drive everything home when it happened. A small crack opened up between the arm and the doubler. With no way to stop the assembly process with glue on everything, I had to move forward and deal with the crack later.
I don’t know why this crack opened up. Perhaps there wasn’t enough glue in this spot. Perhaps the clamping pressure wasn’t sufficient in this area. Whatever the reason, with the tension forces in this chair acting on the joint, it wasn’t going to close back up on its own. But the arm was already shaped, cleaned up and sanded. It was pretty much finish ready at this point. Repairing the crack would have to be done carefully to avoid making a mess of things.
After some careful consideration, I decided to mask off everything around the crack to mitigate the mess of glue that was sure to get everywhere during the repair. If any glue were to get on the surrounding wood, it would be difficult to completely remove and there would be risk of remaining glue impacting the finish. Masking the area off would protect the surrounding bare wood from most of the mess.
Then I turned to a tool that I’ve used numerous times before to get me out of a bind, a set of feeler gauges. I determined that the widest part of the crack was about 0.3 mm and that a 0.1 mm feeler gauge could slide back most of the way. So I laid a bead of glue down on the tape in front of the crack and proceeded to use the 0.1 mm feeler gauge to push the glue back into the crack and spread it around as best as I could. I added more glue as needed until I was confident that there was sufficient glue pushed into the crack. Then I added a clamp to the piece, washed off the squeeze out with a wet paper towel, and walked away for a few hours.
After a few hours, I removed the clamp, removed the tape, and inspected the repair. The tape prevented the majority of the glue mess and squeeze out from getting all over the surrounding area, and it appeared that the feeler gauge was able to get sufficient glue into the repair to make for a strong, tight joint. What little squeeze out did get on the bare wood around the repair was easily removed with a chisel for the corner where the doubler meets the arm, and a card scraper for the rest of the joint. A bit of hand sanding with 220 grit completed the repair.