[Watch the video version above].
If you’re cutting a mortice and tenon by hand then it’s likely things aren’t going to be perfect at the first fitting.
If I’m building quickly and I can get away with it, then I’ll deliberately make some gaps and ensure that they’re on the face that won’t be seen – this can offer a few advantages.
But if both faces of the joint are on show then I’ll aim for perfectly tight shoulders right the way around. Problem is, when you start to put a critical eye to it, you’re likely to find an unwanted gap.
There can be various reasons for the gap – it could just be some crud that needs scraping out. But one of the most common reasons is because the mortice itself has been chopped a little out of square.
If this is the case then the joint might seem to fit perfectly, but when it sits home you’re left with that unsightly gap down one shoulder, and if the rail’s long enough you might spot it running slightly askew.
The Fix – Fine Tuning Your Mortice And Tenon
There’s a quick and easy solution to this problem.
Don’t touch the tenon.
If the joint sits home then you’ll only make it loose by playing around there.
Instead you want to make a very slight alteration within the mortice. We make the adjustment on the opposite face to where the gap is visible. We’ll pare that wall so it kicks out a little towards the bottom. It’s about changing the angle not the fit, so we’re trying to remove as little material as possible towards the top of the joint.
If we exaggerated things to help visualise them, then we’d see that to begin with the mortice walls are parallel but slightly tilted to one side. Our adjustment will take the walls out of parallel so that the mortice is wider at the bottom. A small adjustment will make a big difference, so the joint will still remain a good fit and be nice and tight at the top.
You’ll want to pare just a little and then check, as that may be enough to put things right.
If you’d like to learn how to cut perfect the mortice and tenon with nice crisp shoulders, then check out our Chair Building Video Series.
Or for a faster approach when those inside shoulders won’t be on show – learn the efficient way to cut a mortice and tenon by hand in our Hall Table Video Series.