Woodworking Workbench - Chopping Large Mortises
Parallel lines that are a incredibly useful during the initial phase to make sure your mortise starts out with parallel walls.
With an attempt or two under my belt, I felt confident enough to put the mortise chisel to my workpieces. With a freshly sharpened chisel, I started slow and with each blow, I checked myself for square in all directions. My test pieces took a long time so having to get through 8 mortises seemed like a daunting task.
If memory serves me, the first one took me about an hour. With each subsequent mortise, I shaved off about 5 minutes - no pun intended. The last one only took me about 35 minutes from start to finish.
With each mortise honed more skills. I was able to feel and hear what I was doing. I listened for the changes in sound and could tell when I was reaching the bottom and it was time to leaver out the waste, ensuring I kept the chisel square while executing that move. This produced relatively clean crisp sides. My hands also started to recognize if the chisel was starting to twist as I chopped down and I could correct that.
Lever out the waste so that the next big of material has somewhere to go. A clogged mortise is inefficient. Your energy goes into compacting the chips rather than removing them.
The trick was learning where the bevel of the chisel should facing - towards me or away from me. I started to recognize that the face (flat side) of the chisel would track straight down, while the bevel edge would move material. This is how I got nice square ends right against the knife lines.
I watched a lot of videos and read up lots on multiple forums:
Paul Sellers Workbench Series - he uses a bench chisel to do all the work. Some great tips and tricks through out the segment
Shorter version by Rob Cosman for a quick overview of the process
Full detailed version by Rob Cosman with plenty of useful titbits
Woodworkers Journal - extensive article with great details
Keep checking that you’re chopping square. It helps to stand right in front of the chisel. Also pick one of the longitudinal knife lines to aim for. I’m holding the chisel with my left, so I placed the right corner of the chisel on the right knife line.
Few other tips that might help others:
Sharpen often - a dull chisel just doubles (likely more) the effort. Spend one minute to sharpen up and you’ll smile when you feel the efficiency
Tip from Rob’s video was to draw parallel lines to use as guides to stay square during the initial phase
Start levering out waste early and keep it up. When you make the next chop, the material has somewhere to go when the bevel pushes against it
Use a maker or tape to act as a depth gauge. I’ve already left to large dents in my brand new benchtop.
Wear ear protection - Maybe it was my small workspace or hollow work surface, but the chopping gets loud and isn’t worth hearing damage. The sounds are loud enough that you will still be able to hear the tone/pitch change as you’re chopping. You will also start tuning into the vibrations emanating through the chisel.
Use a larger mallet if you’ve got one. With the small head on my store bought mallet, I missed the end of my chisel more than a few times and smacked my hand. When you’re really wailing down, you don’t want to hit bone!
Music, podcasts or radio - let’s your mind wander from time to time
Warn your neighbours and family members - you will be at this for a while!
Really neat to look at the chunks that come out of the mortise.
Work from both directions. For such deep mortises it will be difficult to to see what what’s going on inside and to clear waste if you try to go all the way from one side.