Chopping Mortises

[Nathan Johnson]

I'm currently working on my bench and chopping mortises for the stretchers in the legs. Using laminated SPF 2x4s and a 12mm bevel edge chisel.
I do not own any mortise chisels. No drill press. No auger bits. So I'm asking for any tips on chopping better mortises.
The chisel is square, with a 25 degree primary bevel and an approximately 30 degree micro bevel.
I seem to wander a bit as I go, and my walls are a bit out of square. Is this just a matter of getting better with practice, or are there any tricks or techniques that are greatly beneficial?

Thanks.

[Hasin Haroon]

Hey Nathan,

Here's a tip that helped me a lot. Mark out all four sides of your mortise with a marking gauge and knife, and then use your knife to score all four sides deeply. Use a chisel the exact same size (or if you can't, smaller) to peel out the wood in between the marks. If you scored them deeply, in pine, you should have around 1/16 to 1/8 shallow 'mortise' that you can now use to register your chisel for all the cuts you'll be making. It'll give you much cleaner side walls compared to the inevitable variation in chisel placement that happens when you're cutting your first mortises. I've seen this method used in a number of places, such as Derek's website.

A lot of folks prefer drilling out the mortise and then finishing up with a chisel but I find that cumbersome and less accurate. The best way (for me) is to size my mortise exactly the width of the chisel I'll be using and chop away.

[Nathan Johnson]

Hey Nathan,

Here's a tip that helped me a lot. Mark out all four sides of your mortise with a marking gauge and knife, and then use your knife to score all four sides deeply. Use a chisel the exact same size (or if you can't, smaller) to peel out the wood in between the marks. If you scored them deeply, in pine, you should have around 1/16 to 1/8 shallow 'mortise' that you can now use to register your chisel for all the cuts you'll be making. It'll give you much cleaner side walls compared to the inevitable variation in chisel placement that happens when you're cutting your first mortises.

A lot of folks prefer drilling out the mortise and then finishing up with a chisel but I find that cumbersome and less accurate. The best way (for me) is to size my mortise exactly the width of the chisel I'll be using and chop away.

Thanks. I am using a mortise gauge (well, the Veritas dual marking gauge) set to the width of the chisel I'm using, but just using the gauge lines. I'll try making those deeper and see if that helps.

[Chet R Parks]

Hi Nathan,
Along with what Hasin said I use 1/8 thick x 1 or 1.5 inch aluminum angle to register the chisel against to maintain a vertical wall. Being an angle ii's easy to clamp to the board. I have several different lengths of angle and use the length appropriate for the board. Good luck with your project.
Chet

[Nicholas Lawrence]

Paul Sellers has a Youtube video on chopping mortises. I found it very helpful, and for whatever reason when I do it that way they end up square.

[Nathan Johnson]

Hi Nathan,
Along with what Hasin said I use 1/8 thick x 1 or 1.5 inch aluminum angle to register the chisel against to maintain a vertical wall. Being an angle ii's easy to clamp to the board. I have several different lengths of angle and use the length appropriate for the board. Good luck with your project.
Chet

Good tip, I can try that. Thanks.

Paul Sellers has a Youtube video on chopping mortises. I found it very helpful, and for whatever reason when I do it that way they end up square.

Yes, his method is what I am trying to emulate. Sure looks easy when he does it.

[David Eisenhauer]

Sounds like these may be your first or at least "firster" mortises and , if so, yes it will get better as you gain experience. In my opinion, the Paul Sellers demo is one very definite way to chop them with good results. Work bench frame mortises are usually large and deep, so the joint will be solid if some small area of the entire mortise is slightly out of plumb due to minor undercutting. I run a small square along the side and end walls of the mortise to check for any "bulges" that will prevent the tennon from sliding in and tend to skip using a square guide to hold my chisel against because I don't have too much trouble ending up plumb. Certainly a wider chisel helps create a more consistent sidewall, but the 1/2" - 12mm size chisel is probably my most used paring chisel. If the wood is hard, a 35* micro bevel may be better, but that is for you to decide. If the $ is available, maybe order a wider chisel for use here and to add to the collection. Also, I don't tend to pound the chisel for maximum penetration when chopping, but just bop it a couple of whacks to take what the chisel gives me. That tends to keep my chisel better in square than when I try to go for deeper penetration by pounding harder.

[Nathan Johnson]

Sounds like these may be your first or at least "firster" mortises and , if so, yes it will get better as you gain experience. In my opinion, the Paul Sellers demo is one very definite way to chop them with good results. Work bench frame mortises are usually large and deep, so the joint will be solid if some small area of the entire mortise is slightly out of plumb due to minor undercutting. I run a small square along the side and end walls of the mortise to check for any "bulges" that will prevent the tennon from sliding in and tend to skip using a square guide to hold my chisel against because I don't have too much trouble ending up plumb. Certainly a wider chisel helps create a more consistent sidewall, but the 1/2" - 12mm size chisel is probably my most used paring chisel. If the wood is hard, a 35* micro bevel may be better, but that is for you to decide. If the $ is available, maybe order a wider chisel for use here and to add to the collection. Also, I don't tend to pound the chisel for maximum penetration when chopping, but just bop it a couple of whacks to take what the chisel gives me. That tends to keep my chisel better in square than when I try to go for deeper penetration by pounding harder.

Thanks for the detailed reply.
Yes, these are my first mortises, other than testing on a couple of scrap pieces. I'm brand new to woodworking really, and this bench is my first project.
12mm was the closest I could get to making the tenons 1/3 the width of the stretchers. I might try playing with the bevel angle...

[ken hatch]

Sounds like these may be your first or at least "firster" mortises and , if so, yes it will get better as you gain experience. In my opinion, the Paul Sellers demo is one very definite way to chop them with good results. Work bench frame mortises are usually large and deep, so the joint will be solid if some small area of the entire mortise is slightly out of plumb due to minor undercutting. I run a small square along the side and end walls of the mortise to check for any "bulges" that will prevent the tennon from sliding in and tend to skip using a square guide to hold my chisel against because I don't have too much trouble ending up plumb. Certainly a wider chisel helps create a more consistent sidewall, but the 1/2" - 12mm size chisel is probably my most used paring chisel. If the wood is hard, a 35* micro bevel may be better, but that is for you to decide. If the $ is available, maybe order a wider chisel for use here and to add to the collection. Also, I don't tend to pound the chisel for maximum penetration when chopping, but just bop it a couple of whacks to take what the chisel gives me. That tends to keep my chisel better in square than when I try to go for deeper penetration by pounding harder.

David,

The best advice of the bunch. This is a case of slower is faster, less is more. Bench or pig sticker it should be tap, tap, lever, tap, tap, lever, repeat till finished. Going Conan makes for a bad mortise and will slow the process.

ken

[Jim Koepke]

Just to echo what others are saying, it is like learning many tasks in life, work toward accuracy and speed will come naturally with time.

jtk

[Joe A Faulkner]

It is not critical for your mortises for your stretchers in your bench to be a perfect tight fit for the tenons. So don't sweat it if the tenons are not square. If you draw ore the joints you will get a strong, sturdy joint.

[Nathan Johnson]

I'll just say it's a good thing the apron is going to hide my first one. Yikes.

[David Eisenhauer]

Work your way around the table and then re look at the first one. It should be OK, especially if you are drawboring them (good idea) as Joe says. If you are really still unsatisfied with the first one, you can trim the mortise out a little to clean it up and then glue a thin shim on the tennon (on the correct side) and slowly skin the fat side of the tennon down to the correct thickness. That can be done with a chisel, router plane, shoulder plane, flat rasp or saw if you can hold it to the line. Plane shavings (curls) make especially good tennon shims for minor increment changes or you can glue up an over fat shim to the side of the tennon and then recut it with a saw and start all over with that side.

[Patrick Chase]

Paul Sellers has a Youtube video on chopping mortises. I found it very helpful, and for whatever reason when I do it that way they end up square.

I don't use Sellars' technique, but it's probably worth noting that he demonstrates chopping mortises with a bench chisel, which is exactly what the OP needs. IMO there are more efficient ways to go about it if you used pigstickers.

[steven c newman]

IF you had any, of course....