WIP - mortise chisels

[zhyla]

A friend of mine requested a 1/4" english mortise chisel. Mortise chisels are different than the regular paring chisels most people are familiar with. They're made for pounding into a piece of wood to cut a rectangular slot for tenon-and-mortise woodworking joints. So they're large and beefy. This design is a traditional pattern known as the "English mortise chisel". They stopped making them in the 50's, though there is at least one maker that recently started production.

I'm using 1/4" 1095 for this. Here's the blades after cutting and some cleanup:

I'm making 2 so I'll have one too.

So that was all pretty easy. On to the bolster! This was the usual kind of pain that comes with making square holes with round bits. I drilled a few 1/4" holes and then used a 3/16" end mill to clean it up. Followed by some awkward filing. I used 1/4" 1095 for this as well.

It may not be super obvious but the bolster isn't cosmetic, it's a load bearing part. The rectangular hole is flared front to back to match the taper on the front portion of the tang. This allows all the force of a hammer blow on the handle to be transmitted to the blade. Otherwise over time (or maybe immediately) the tang would eventually split the handle.

I'm pretty happy with the bolster fit. It's not the most perfect oval but it's not that bad. The bolster could be thicker. I think I will actually heat treat it and temper to something really low. I suspect these are usually made from mild steel but much thicker.

That's where I am now. Need to make another bolster for the 2nd chisel and figure out what I'm doing for the handle. Traditionally the handle is press fit onto the tang. This makes the choice of wood important so it doesn't split during installation. Hickory, beech, ash, red and white oak are the common ones used. What a boring list of woods!

Question: My thought was why not just epoxy the handles like I've been doing the wa-handles on my kitchen knives? My friend is concerned the epoxy might crack but I don't think so, I think it will actually be more robust than a press fit over the long haul. Anybody have any thoughts on this?

 

[Stacy E. Apelt - Bladesmith]

It is best to make an end cap and peen the tang over in a tapered hole. that transfers the hammer blow directly to the cutting edge.

 

[zhyla]

It is best to make an end cap and peen the tang over in a tapered hole. that transfers the hammer blow directly to the cutting edge.

I don't disagree with that but the goal of this project was more to make a traditional English mortise chisel. They just made them this particular way.

Still trying to figure out exactly how to do the handle mounting. I have some big cherry scraps that are large enough, but I'm not sure it's the right wood to get banged on. It is pretty though (for a tool handle):

I should probably just go find some beech...

Traditionally the tang tended to be very heavily tapered and was press fit into a tapered rectangular hole. I learned this after I cut the tangs for these. I think I will go with the epoxy route, just bore a hole that will accept the tang, fill with epoxy, squish together. Won't make re-handling very easy but it will work.

 

[John L]

It is best to make an end cap and peen the tang over in a tapered hole. that transfers the hammer blow directly to the cutting edge.

An English mortice chisel is not struck with a hammer but pushed.

 

[zhyla]

An English mortice chisel is not struck with a hammer but pushed.

This is incorrect.

 

[John L]

This is incorrect.

I have several complete sets of older English mortice chisels and not one has hammer marks. Worked in a woodworking shop for over 40 years and was taught and practiced to never strike this English style mortice chisel.

 

[zhyla]

That's really interesting. I don't want to start a big fight or anything, but it's still incorrect. The design is clearly made to transfer significant amounts of force to the edge. There's plenty of examples of these chisels that have been really beat on. Most of them have probably been rehandled over the centuries.

But don't take my word for it, here's Mr. Roubo himself showing us how it's done:

 

[John Katt]

Use JB weld It will outlast the wood handle

I have to vote for using a wood mallet with this chisel, I just read several articles about the revival of the English mortise chisel, and most reference the extra thick handle and large bolster as being designed specifically to take the abuse of a wood mallet (soft wood mallet no hammer marks)

 

[Alan G.]

Interesting. I am far from an expert, but I just finished a dining table for our house and used mortise and tenon joints for most of it including hidden and through tenon joints. All of the instructions I found said to use a wooden mallet to strike the chisel and there is no way I could have done it without this.

Yours are looking good. One concern I would have based on the chisels I purchased and others I saw is that for only a 1/4 inch mortise, your chisels are very wide. The smaller one I purchased was almost square (3/8 I think). You are going to be limited in your ability to leverage the chips out as you cut deeper into the wood. Unless your mortise is very long your chisel will hit the sides of mortise. May not matter though depending on what you are making.