I recently received an email inquiring about the reason I made the tenon before the mortise in my new book, Joined: A Bench Guide to Furniture Joinery. I knew I’d be asked this one as I’ve taught it the other way around before. In my article in Issue Four, I wrote, “I prefer tackling mortises first.”
The truth is that in regular shop practice, it just depends on my mood. The reason it doesn’t matter is because I size both the mortise and the tenon to the width of the mortise chisel. The only advantage to chopping the mortise first is that you can final-fit the tenon right away, rather than waiting to pare it after the mortise is chopped. In batch production for an entire table, that’s really a moot point. In real life, I just want to get in a groove, so I do all of the tenons together, and all the mortises together. In whichever order. If I’m feeling focused and ready for meditative, close work, I do tenons. If I feel like smacking something, I grab my mallet and “pigsticker.”
If you saw the tenon too thin, it’s not like you are going to downsize your mortise a hair. The chisel is your standard.