Thread: Tips on chopping mortise holes square

If the mortise is big enough it's always handy to use a small adjustable/combination square to check. Stock against face and rule in hole.

When I started learning to chop mortices I really struggled. What made a difference for me was to reposition myself such that I was looking at the front/back of the chisel rather than the side. This allows me to see when the chisel was canted to one side. Then for squaring the ends of the mortise, I would look from the side to ensure they were square in the other plane. I hope that makes sense.

After chopping quite a few mortices since then, I have found that my hands just hold the chisel square without too much thought. I guess that like most hand tool skills, repetition helps a lot.

There are still times though, where I do pull out a guide block for cleaning up a tricky edge. It’s a journey.

Good luck, and stick with it. It’s a great skill to have.

Practice!

Why don't we say "chisel" or "cut". Chop reads like you're getting firewood.

Originally Posted by rod1949

Why don't we say "chisel" or "cut". Chop reads like you're getting firewood.

For the same reason I don’t drive my bicycle or ride my car? Honestly I have no idea. That’s just what I heard people say when I started out, so I say it too.

When presented with grammatical or pronunciation questions, I generally consider what the Queen would say. In this case however, I don’t believe she talks about cutting, chiselling or chopping mortices all that often, so we’ll have to figure it out ourselves.

Cosman has some good tips on at least two recent videos, maybe three which were made, probably in the last year and a half.
I think it may well be the best content I've seen on the subject.
One where he's chopping a very narrow one for a chair component? that was worth watching.

I use a block but for registration of a tool be it a flat chisel back, precision steel rule from a engineers protractor, or even a 7 or 8mm precision square block, which can be used to check, mark or burnish the high spots when pressed against with force,
and for walls can also be used as a both a checking and marking tool using dirty graphite...
which might be a good idea for through work if you really like to waste time like me.
I reclaim African timbers and have to plug mortise holes so most are visible and also structural.

(Final edit, I've only realised that this thread is about chopping mortises, sorry about going off topic quite a bit)

Checking
SAM_3336.jpg

Burnishing or transferring graphite onto the work, pushing to the far wall is much more reliable way to get a true witness mark, than simply pressing.
That's the outside of the mortise wall that is being marked below.
SAM_3649.JPG

Either checking or marking a handy tool, notice there is still a hair line gap still on the left side, and a lump or the right.
When no shadow line is present is how the tool can be used

SAM_2945.JPG
Or it can be used with graphite, or both.
SAM_2942.JPG
An easy tool to use and misuse, (timewise leading to something resembling some Japanese scraping techniques)
but a good tool to make one aware of exactly what their doing.
(it's stopped me from approaching the work like above, in favour of turning the work around when possible, i.e not upside down)
Good lighting essential, and I reckon cast iron might be a lot more effective than aluminium, as it wears off fast.


If intending to chop mortices using a block...
I found doing this led me to bruising the timber and prone to excessive undercutting of the work,
Whilst possibly alright for dovetails, not good for mortises, or for making a groove on a shooting board.
Enjoyable wee watch though.
Fergal Spain - YouTube

Originally Posted by rod1949

Why don't we say "chisel" or "cut". Chop reads like you're getting firewood.

Possibly it goes waaaaaaaaay back to when carpentry was performed using only an axe and an adze; both tools were invented in the Stone Age. There is a tool called a mortise axe and this was used for making heavy framing.

I've heard many say that an uneven bevel is alright, but not for mortising.
I'd reckon a good going over the chisel is a good idea.
Is the chisel an even thickness, is the handle in line with the tool, or wonky and off to one side?

Those are important things to make sure before using, and if one has a choice of non wonky chisels,
I would choose one with a handle in line with the tool, not a cranked handle, if I had the choice, for chopping.

And since were talking about chopping
I might as well describe how I would go about chopping large mortises
I drill most of the waste out, but like keeping a line for final paring, so chop away from it, (which you can't do with the block.)
The closer to the line you can get, the less diving your chisel will do/the more you can stop from happening.

If you can keep it from being perpendicular, as that will end up diving in the cut with anything but a chisel with a belly.
I don't have any bellied chisels, but see them working effectively in David W's videos.

However, I don't know where you'd get chisels like that.



This is just making a line to register the chisel in, and not the knife line
SAM_3724.JPG

So I can ensure that I won't have any tearout from the drill
SAM_3732.JPG

More noticeably more of an issue with a mortise (sorry didn't have a piccy of the chisel)
as there is chance of tearout, so a good chop out of the sides, still a ways from the actual gauge lines.

Maybe I need to buy some nice drill bits for wood, have loads of cheapies, which never felt all too eager to try.
Instead I use ones for metals, but get by doing this way.


SAM_3878.jpg SAM_3881.jpgSAM_3883.jpg

That's about all I can say for large mortises.
Edit
Some do two narrow mortises with a pig sticker and chop out the middle.
Didn't have the guts myself, but had a play.
Cosman's had some tips on what I could have done to improve things with this method.
(if wanting to go full Neander)

Tom

Ask 10 woodworkers and get 20 opinions!
I would recommend Paul Seller's Youtube channel - he has several demonstrations on chopping mortices, including one done against a clear sheet (glass?) so you can see what is going on inside the mortice hole.
I find Paul's techniques are generally simple and to the point and he does not promote specialised tools etc. He has developed techniques that are practical and easy to follow.

Bruce

Originally Posted by LanceC

For the same reason I don’t drive my bicycle or ride my car?

In the United States, you're allowed to ride IN a car - while someone else is driving - without violating the word usage rules.

Originally Posted by LanceC

When presented with grammatical or pronunciation questions, I generally consider what the Queen would say. In this case however, I don’t believe she talks about cutting, chiselling or chopping mortices all that often...

No, but ask her how to to a field repair on a Land Rover, and she might have words to offer. She did, after all, work in the Motor Pool during World War II.

My preference is drill out the excess wood. Use a sharp mortise chisel. Then use a corner chisel.

No, but ask her how to to a field repair on a Land Rover, and she might have words to offer. She did, after all, work in the Motor Pool during World War II.[/QUOTE]

How so ?
The Land Rover is Post WW11.
I doubt she made the time to keep up to speed once dating the Greek.
Although come to think of it he had rather a special Landy.
And yes it’s still sort of in the family, Tata being an Indian company.
Victoria would be pleased.
H.

Originally Posted by clear out

Originally Posted by Bill Houghton

No, but ask her how to to a field repair on a Land Rover, and she might have words to offer. She did, after all, work in the Motor Pool during World War II.

How so ?
The Land Rover is Post WW11.

Yabbut, it's a British car - so much of it probably resembles pre-WWII mechanical stuff sufficiently to be recognizable.

Including, no doubt, the highly reliable electrical system.

You mean. Lucas. ‘Prince of darkness’.
H.