Thread: How Do I Improve My Mortise Chisel Technique?

In the case of a mortice chisel, the oval handle is an advantage in orientating the direction of the blade that you can readily experience.

The other advantage of the OBM chisels is that the blades are tapered on the sides (trapazoid), which aids release.

The disadvanytage - in my experience - is that they do not work well with pre-drilled mortices, where the straight-sided LN is better. Still, I do not pre-drill mortices.

Regards from Perth

Derek

Originally Posted by derekcohen

Why do you want a "router quality finish"? The tenon does not care. As long as it is a good, even fit ...

Regards from Perth

Derek

What is this apostate talk! Derek, I thought you were the number one proponent of the immaculately smooth joint interior – or is that just with dovetails?

Originally Posted by derekcohen

The other advantage of the OBM chisels is that the blades are tapered on the sides (trapazoid), which aids release.

The disadvanytage - in my experience - is that they do not work well with pre-drilled mortices [...]

They aren't meant to be used in pre-drilled wood. The whole point of mortice chisels is that they are efficient at removing wood swiftly, cleanly and accurately by themselves. If you try chopping out drilled wood with a tapered mortice chisel, the holes will steer the chisel and it will be near to impossible to obtain a straight mortice... and by the time you straighten it all up, it will likely be oversize.

Thumbsucker, sash chisels were made for cutting mortices in window sashes, so if the work you envisage doing is commensurate in proportions to a window frame, then the Lie Nielsen (sash) chisels will be more than up to the task (I have a set of LN mortice chisels from 1/8" up to 3/8" and they are good chisels – though I'd prefer carbon steel blades). If you plan on making a lot of house doors, garden gates and railway carriages, then in my opinion, you would be better off with oval bolstered pigstickers.

Originally Posted by Woodwould

What is this apostate talk! Derek, I thought you were the number one proponent of the immaculately smooth joint interior – or is that just with dovetails?


They aren't meant to be used in pre-drilled wood. The whole point of mortice chisels is that they are efficient at removing wood swiftly, cleanly and accurately by themselves. If you try chopping out drilled wood with a tapered mortice chisel, the holes will steer the chisel and it will be near to impossible to obtain a straight mortice... and by the time you straighten it all up, it will likely be oversize.

Thumbsucker, sash chisels were made for cutting mortices in window sashes, so if the work you envisage doing is commensurate in proportions to a window frame, then the Lie Nielsen (sash) chisels will be more than up to the task (I have a set of LN mortice chisels from 1/8" up to 3/8" and they are good chisels – though I'd prefer carbon steel blades). If you plan on making a lot of house doors, garden gates and railway carriages, then in my opinion, you would be better off with oval bolstered pigstickers.

Do I hear an echo here?

WW agreeing with me? The sky will fall in!

Regards from Perth

Derek

Originally Posted by Mr Brush

Sam - I use Charlesworth's method all the time for dovetails, i.e. sighting the chisel to a square sitting on the bench behind the workpiece. It really does work brilliantly.

As for mortise chisels, well there's always one of these

English Mortise Chisels by Ray Iles at Tools For Working Wood

D2 steel anyone??

Mr B

Thank you for that link. Most interesting. I have future project for sliding glass doors and, although it is quite a way in the future I am sourcing tools in readiness.

Our own Harold and Saxon also produce pig stickers. I think the material is HSS.

Regards
Paul

Originally Posted by derekcohen

WW agreeing with me? The sky will fall in!

I just looked, and it's still in place!

Whew! 'Bout time you two kissed & made up.

On to serious matters. Yes, I think there is a lot of unnecessary angst about perfect mortise sides. If there is about 50% wood to wood contact and the voids aaren't too horrendous, your average joint is going to be way strong enough. Probably at least an order of magnituide better than a typical dowel joint used for the same dimension joint.

From my readings of wood technolgy, I wonder about how good a router mortise really is. Pounded or polished wood fibres, as you often get off routers (particularly with dull cutters) do not accept glue well. Such joints obviously work well enough for most purposes, at least in the short term, so it may also be an unnecessary worry too - time will telll. In the meantime, I'll stick with mortises either cut with my (sash) chisels or my hollow-chisel machine. To be honest, I tend to use it nearly all the time, now - it doesn't drown out Mahler & Mozart, and is sooo quick.....

Cheers,

Hi TS,

I tend to agree with the general consensus comments so far, that perfectly matching of perfectly flat faces for mortices and tenons is not necessary and my be counter-productive to a strong joint. I also agree with the thought that such joints will squeeze out most of the glue when being fitted.

Chairs probably provide one of the most testing conditions for mortices and tenons, the joints are small and the loading is high and often multi-directional. I don't recall coming across a chair where the glue failed in a mortice where PVA or epoxy glue was used, usually the timber fails I think. With the smelly glue, (hide glue) joints do or may become loose, but the benefit of this glue is that that joint can be disassembled and reglued.

Others with a lot more experience than myself might like to comment on hide glue joints and failure rates.

My point is that, (as evidenced by multiple magazine articles) when tested to destruction, mortice and tenon joints often see the wood failing before the glue joint, so perhaps, as others have said, perfectly flat and sized mating surfaces are not necessary for a competent glue joint.

Cheers
Pops

I've had no formal instruction in mortising aside from watching my father, a highly skilled artisan, cut mortises using what we'd call firmer chisels that had been sharpened to a more obtuse angle. What I do is entirely from my own experience, there are probably lots of better ways of hand cutting a mortise.

I'm currently using japanese mortise chisels. This is simply because I came across some that were heavily discounted a few years ago. It's an incomplete set that I intend filling in some day.

I keep them sharpened to about 35 degrees, I don't use a secondary bevel. I don't think there are any absolutes in the angle to sharpen to. However, I read up a bit a while back and from that I gleaned angles from about 25 (soft woods) through to 40 (ebony) are routinely used in the country these chisels are made. The more obtuse the angle the greater the support to the edge and the longer it lasts.

I've been cutting a few mortises recently and the best run I got was four 1/2" by 3" by 4" mortises in vic ash prior to resharpening. However, if I strike tougher sections in the timber I can be sharpening after each mortise. Mostly this just requires a lick on my 3000 and 6000 water stones, that is unless I've done something daft or got unlucky.

The japanese mortise chisels have a concave back and are very slightly tapered in width, being wider at the tip. This helps to stop the chisel from jamming in the mortise. I use several different weight hammers, depending on the application.

I don't agree that you have to be end on to the work to make a good mortise. However this can help when you first start out. I've made mortises lying on my back (yes wearing goggles) and on my side, not ideal but straight forward enough.

The key is to get the angle right and to maintain it. For this it can really help to have something to sight your chisel against.

One thing that I think is important is not to cramp the body up when working. If you hold the chisel and hammer/mallet out away from your body it helps as you can take advantage of perspective to sight the chisel and keep your blows square to the blade.

I've seen people adopt a comical straight-armed approach to making mortises where they hold the chisel and hammer or mallet at the absolute fullest extension of their arms with elbows locked out straight. This is taking the above approach to an extreme. I think it's ridiculous and can only tire their joints and reduce their capacity to concentrate a slight bend in both arms feels much more comfortable for me.

I choose different weight hammers depending upon the delicacy of the joint and the density of the timber. I never really put my shoulder into the swings but instead rely more on the deceleration of the mass of the hammer as it strikes the chisel to drive the point in.

When I'm making a joint where it really matters what the external appearance looks like I start out the first 1/8-1/4" very delicately and pare a complete trench first. Then I start at the centre and make a series of intersecting cuts slicing wedges out of the joint. The first few cuts can be reasonably shallow as I form the void for the wedges to be driven in to. I do one layer of wedges at a time and then once again start at the centre.

When I first start with a new batch of timber it can take a little practice to work out exactly what size to make my wedges. In softer timbers the wedges can be larger. However, if I want a really smooth joint in a soft timber I'll use a lighter hammer and take smaller cuts.

I've found the key to making the edge on the chisel last is to use the chisel to cut the fibres not as a lever for pulling the chips out. I've seen people levering on chisels to work them loose, this just ruins the edge on the chisel causing the sharp edge to fatigue and begin to break off in the joint. Also, when I first start at the centre of the joint I keep the chisel on an angle to the surface rather then driving it directly in.

As to your question about voids, I'd agree with others, provided that the joint is sound overall, it shouldn't make a material difference. If you are concerned that it will weaken your work piece then I'd suggest taking smaller amounts with each cut.

This is probably my longest ever post so feel free to query what I've said as it is a bit of a ramble.

Cheers

Horaldic