Cleaning out a mortise, with photos.

[Dave Shepard]

I took some photos today of boring and cleaning out a mortise. This is how I do it, others may have a different method. I cut a 1.5"/1.5" mortise, 6" long and 4" deep. It took me 12 minutes messing with the camera, and using the Boss boring machine on the slow setting, which is 2.25 times slower than the fast setting. In production framing, you would layout an entire timber, then bore all the joints, then clean them up, so this joint would go much faster normally.

Score the ends of the mortise, and the sides if it is not a housed joint. I use the chisel.



Bore the mortise. For best results, use a bit the same width as the mortise. Bore the ends first, then the middle.



Clean up the sides of the mortise, use your chisel as the gauge. Make sure the chisel fits everywhere, if it binds, cleaning the ends won't be much fun.



Put the chisel in the score mark you made on the end of the mortise and drive it home.





Pull the chisel into the mortise. You now have a perfectly clean and square end to your mortise.

[shinnlinger]

Nice looking mortise..  What size is your Saco mallet?  I have a # 3 split head like you have, but find it a bit large for using all day.  I got it because I liked my old #3 press fit, but the split heads seem to have have more weight, or maybe I am just getting older.....

When I bore mortises, I like to skip bit widths and then go back and get the peices I missed, I find it bores straighter if the bit has the same material, or lack thereof  on both sides....

It looks like you need some more horses.....

Dave

[Dave Shepard]

That's a 3# Garland mallet. That block is 14" tall, so it is just right for boring on the floor. I also just sit right on something that size. I think a lot of timbers were worked by sitting on them, especially when they are the size of these Dutch barn timbers. That block is just an off-cut I used for demo purposes.

[Thehardway]

I assume that is pine you are working with?

[Dave Shepard]

Eastern White. Clear hardwood wouldn't make much difference in time, a knot, however, could make you earn you money. :D

I forgot to add, for that last chop to be effective, you must use a bit that is the same width as the mortise, and you have to get it up close to the end of mortise. That is why you bore the two end holes first, then deal with the middle.

[jander3]

Thanks for the photos and write up.  I appreciate understanding how others approach these tasks as it helps me refine my technique.

[Dave Shepard]

I have a couple of other photo groups I might post up. I usually am so involved in the work I forget to take a lot of photos.

[canopy]

That is the method I learned and using the chisel for scoring is a nice added touch. The other thing I do is drop in a speed square to assure the sides are straight down and the bottom is deep enough. A time saver I came up with is before making the big holes, I use a small drill bit right up against the 4 corners to ease working the corners.

But in my experience cleaning the ends out is much more difficult than just putting the chisel on the edge and driving it home. Instead It goes a little and stops. So it takes some number of minutes working at each end to get through, sort of like working the sides but only more difficult due to the limited space.  Might I be doing something wrong like not pounding hard enough? I work with teak if that makes any difference.

[Dave Shepard]

I haven't worked teak, but it sounds hard. I've used this method in fresh pine, red and white oak, ash and cherry, as well as some 200 year old oak and black ash, and it works well in all. If you've bored the hole right up against the end of the mortise, you are really only cutting wood in the corners. If you can't chop straight down the end, you may have to take small bites and work you way to the line. I do use a combo square to check the sides off of the face, but after a while, you get pretty good at chopping straight down by eye. As far as force, pine chops easy, of course, old hardwoods, you might have to hit pretty hard. That is why you need to make sure the mortise is the correct width, or you end up with a chisel bound in the hole.

[Jim_Rogers]

One thing I posted in another thread that should be also mentioned here is that the sides of the mortise should be processed first.

And you should process, that is clean up, the side closest to the layout face and make sure you get it to the correct offset before you make the mortise the width it's suppose to be.

This helps the faces of the timbers to align properly.

After you have processed the layout face side of the mortise and you have the mortise the correct width then you can chop the end grain and your chisel hopefully won't get stuck in the mortise.

And you should go right to the line with the first chop. Start out a little and them move in.

Remember what the old man said when he was driving the bulldozer: "you can move a mountain with this thing, if you do it a little bit at a time....."

The same thing goes with chopping end grain.

Jim