Cutting mortises wider than your chisel

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  • Marc Mitsialis
    6 January 2017 at 8:38 pm #143946

    Hi,

    I am looking for tips on using Paul’s Mortising technique for cutting mortises wider than the chisel width.

    Thanks,
    Marc

    Thomas Angle
    7 January 2017 at 12:44 am #143956

    Depends on how wide the mortis is, If it was say 2″, you could cut two parallel 3/4″ mortises and then clean out the 1/2″ in the middle.

    Hugo Notti
    7 January 2017 at 1:26 pm #143971

    Sounds like a good idea, because this will get you clean sides.

    If I wanted to cut a mortise of 1″ and had a 3/4″ chisel, I would probably do the same chopping twice, once on the left side, once on the right side, and pay special attention to the side that will be cut second, because there is no support for the chisel. I would probably also make a deep knife wall along the grain to make sure I get a clean start.

    Dieter

    Sven-Olof Jansson
    7 January 2017 at 5:49 pm #143975

    Hej Marc,

    Would twin tenons and mortices be an alternative? They might result in a stronger joint, as the glue surface will double, the end-grain to long-grain surfaces reduce, and the shoulders increase.

    /soj

    • This reply was modified 6 years, 8 months ago by Sven-Olof Jansson. Reason: Grammar
    David Perrott
    8 January 2017 at 3:09 am #143991

    You can also drill out the waste with a brace and bit. Drill Half way from each side. Then clean it up with a chisel. Just did this method to make a few mallets and large mortises on a workbench.

    Marc Mitsialis
    8 January 2017 at 9:54 am #143992

    Hi,

    Thanks for all the advice.

    I like the idea of using a smaller chisel to make two narrow mortises and cleaning the waste in the middle suggested by @tomangle. This will assist in creating clean, sharp and square largeer mortises. I will use this preparing the legs for the bench I am working on.

    My main issue is the mortises where the width is slightly wider the my chisel. I currently only have 6mm, 16mm, and 25mm chisels. Where I have to cut mortises 10mm, 20mm, or 30mm wide this won’t always work. This is mainly my inexperience in sizing my joints appropriately to the wood dimensions or not appropriately converting the reference designs from imperial to metric dimensions and my available tools. Thing will improve.

    I will be acquiring more chisels and other tools slowly. I just bought (as a birthday gift to myself) a plunge router, Stanley #4 and Record #5 second hand. I was lucky and got all three for less than the current new price of a Stanley #4 where I live. Next steps is a decent set of sharpening stones.

    Thanks for the advice @tomangle, @dperrott, @sojansson, @hugonotti

    Happy woodworking,
    Marc

    Sven-Olof Jansson
    8 January 2017 at 3:22 pm #143998

    Thanks Marc,

    As you have a 16 mm and a 25 mm chisel, perhaps an alternative could be to drill out the waste of the mortice, and then pair along the cheeks using those wider chisels?

    /soj

    Ed
    9 January 2017 at 12:27 pm #144018

    I just wouldn’t do this. The chisel defines the width of the mortise. Work to the tools that you have, i.e., use 6, 16, and 25mm mortises. Otherwise, I am afraid you will find that the chisel is pushed sideways or twists when trying to make the mortise in multiple passes and you will not get the accuracy you need. Only the trick of taking out the center last seems to have any chance of working, but even then I suspect the center will be weak and will breakout before you want it to.

    Hugo Notti
    9 January 2017 at 9:01 pm #144051

    While it is of course best to cut a mortise the size of an available chisel, I am sure, it is not too uncommon to do otherwise. I can imagine many reasons to do so. There might be little space for complex joinery, so the tenons are quite small already, and you don’t want to reduce them any further. Or you are cutting a mortise for an existing tenon for a piece of furniture you are restoring. Through-tenons might look odd, if too small, even if they would be strong enough. There might be a specific drawing you want to follow to the point. Or you are simply a newbie woodworker with a restricted budget and you know, that your mortise hole must be a bit larger than your nearest chisel. And, I am sure, I would not like to reduce my designs to exactly the tools that I have.

    And I think, it is very good to collect working methods for this. I am sure, that using a too small chisel is not guaranteed failure, it is more challenging only. But still much easier than using a chisel that is too wide 😉

    Dieter

    Marc Mitsialis
    9 January 2017 at 9:32 pm #144054

    Hi, All!

    Thanks for everyone’s’ guidance. I have followed @tomangle’s advice on cutting on each face of the mortise, then cutting out the middle. I post my results, below.

    I am very satisfied with the results. Some accuracy and control need to be developed, I little too much undercutting and lever marks on the one edges.

    The process I followed is as such to cut the 18mm mortise:

    Cut the left face with the 6mm chisel
    Cut the right face with the 6mm chisel.
    Roated the leg and repeated on the other side.
    Then used the 16mm chisel to gently chop out the centre piece.
    Rotate the leg and gently chopped the remainder of the centre piece.
    Carefully pared the faces and ends with the 16mm chisel.

    I have used a slightly modified method to begin the mortise of a through dovetail mortise of 33mm. I did the first pass using the 6mm chisel, then using then used the 25mm chisel for the remaining side of 27mm. I could have done two passes using the 16mm. Although this approach was successful, I will do the remaining three using the 6mm for the edges, then clean up the middle with the 25mm. The added resistance and support of the middle section helps to the chisel remain square.

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    David B
    9 January 2017 at 9:59 pm #144065

    Did you scribe a knifewall on the sides of the mortise to ensure you stayed within your ultimate width? I ask b/c it looks like it was just a pencil line and hence it also looks like the mortise isn’t exactly straight on the edges.

    Sven-Olof Jansson
    10 January 2017 at 12:57 pm #144071

    I too would be very happy with that result!

    /soj

    Marc Mitsialis
    10 January 2017 at 1:01 pm #144072

    <quote quote=144065>Did you scribe a knife-wall on the sides of the mortise to ensure you stayed within your ultimate width? </quote>

    Yes, I did scribe a knife-wall. I wanted to test @tomangle’s advice and my ability to implement accurately. Therefore the knife-wall was 0.5mm inside the pencil line.

    <quote quote=144065>I ask b/c it looks like it was just a pencil line and hence it also looks like the mortise isn’t exactly straight on the edges.</quote>
    The knife-wall was purposely 0.5mm inside the pencil line, so I have a buffer to correct my inexperienced mortising

    All the near edges are clean, but the far edges are not. So I need to develop my work on the far face. I also need to pay attention to the edges when levering the waste out.

    All learning and experience.

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