I just got my first mortise chisel from my dad and I’m trying to practice chopping my first mortise. I started by just chopping in a straight line on the wood and after a few chops moving up as I went the face grain started tearing out and the wood splitting on the sides of the mortise.
I thought then maybe I should use a marking gauge to cut the face grain to prevent tear out so I set the gauge to the mortise and creating some knife lines on the edges and tried again. This time a little better, but still ran into issues.
I’m wondering if this is due to my bad technique or maybe my chisel isn’t sharp enough? I’ve tried both ash and walnut and had the same issue. I’ve watch videos of people doing this and they don’t seem to have any problem with this issue so I’m wondering what I’m doing wrong.
Replies
It sounds like you are splitting the wood more than cutting it. Think of splitting firewood with an axe. You don't mention whether the chisel was new or used, but either way making sure your chisels are sharp is the first priority and the key to success. Learning to sharpen and tune your chisels is the first step to having success with them. Make sure the back is flat and polished and then move on to the the primary bevel and last the secondary insuring both are square to the edge. A sharp chisel can shave hair off your arm as effortlessly as a razor.
Agree, also there are a couple of other things to help and recommend you try the technique used by Christopher Gochnour. Drill a hole close but not right at one end of the mortise after using your marking knife. Once it gets started straight its easier to kept everything in line, Even 1/8" makes a difference as something to register the sides of the mortise chisel. Keep practicing your sharpening and you can do it.
You should definitely be marking or knifeing in lines. But it sounds like you need to sharpen.
Put a piece of wood in your vise, end grain up. Use your mortise chisel, hand held, to try to pare off a thin shaving of the end grain. If it won't take a nice shaving, it's too dull.
The mortise chisel is a Marples blue chip mortise chisel in 5/16th so it's used, but I'm not sure it was ever actually used by the condition it's in. There is no secondary bevel like I see on some mortise chisels. Based on the feedback here I'm going to go ahead and try and test to see how sharp it is and then attempt to sharpen it. There seems to be a lack of videos on how to sharpen mortise chisels, but I'm hoping I can follow the same principals as a bench chisel to some extent.
Don't forget to flatten the back. Marple chisels are decent mid grade chisel but they are mass produced and I'll guarantee if the chisel hasn't been used or sharpened the back is not flat. If the back is not flat you will never get the best cutting edge.
A mortise chisel needs to have sharp corners between the face and both sides, as well as a sharp cutting edge. Ideally, the edges should be the same width apart all the way up the chisel as the width of the cutting edge, on the face side; but the body of the blade should also be trapezoid to reduce the chance of the chisel binding in the mortise.
If those corners are not sharp, or have any roughness, the chisel will leave ragged sides to the mortise as you cut down. This is because the chisel, as you wallop it, goes backwards (away from the bevel side) at the same time as it goes down. Sharp corners between face and sides will cut clean sides to the mortise as the chisel comes back & down. The trapezoid blade shape means that ONLY those corners contact and "plane" the sides of the mortise.
It does help to define the mortise sides, before you start chiselling, with deep-ish knife lines. Personally I prefer the wheel marking gauges with a double knife-wheel, making first light cuts then deepening them with a couple more passes and more pressure on the gauge.
A cutting gauge seems to make better lines than those scratching gauges with two points - although many can make the latter work just as well and have done for centuries. :-)
Lataxe
Starting with a drilled hole at one end is a good idea. Chopping vertically, bevel towards the hole, it the way I do it.
Note that the ends are less important to keep clean if they are covered, as is usual, by the beauty shoulders of the tenon. The essential areas of importance are the sidewalls - keep them vertical and tight to the tenon cheeks.
The two essential techniques to employ:
1. score the outline cleanly and deeply. Sometimes it helps to pare away the top (to a depth of about 1-2mm. This preseves the top edges. It also aids in guiding the chisel.
2. Take very small bites with a (sharp) chisel. Small bites being 2-3mm
http://www.inthewoodshop.com/Furniture/MorticingByChisel.html
Regards from Perth
Derek
All the suggestions given here are good, though I'd suggest a couple things more. 1., drill two centered holes in the mortise about a ¹⁄₁₆" to an ¹/₈" away from each end down to the mortise depth. That way you know when you've reached the bottom and don't keep digging your way through to the opposite face of the board. 2., If you don't drill first, start about ¹⁄₈" from each end with the back of the blade facing the end instead of the other way around so you won't blow out the knife wall/scribe line/gauge line. 3., Finish the rest of the mortise first before paring the ends. There are many videos online. With the ones from Fine Woodworking and Paul Sellers you can't go wrong.
A video of mortise chopping is a very useful thing. There are various styles: with and without a drilled starter hole; small digs or deeper chops; levering out the waste as part of each chop or doing it later......
Personally I admire the Chris Gochnour style as seen in the video series on the Enfield cupboard. But here's another very short (5 min 30 sec) vid that mentions the basic sharpening process for a mortise chisel before going on to show the action via a window into one side of the mortise being chopped.
https://www.youtube.com/watch?v=FYDqeQeov7o
Lataxe
Great video. The one that follows that in my particular feed queue is this one: (28) Cutting a Mortise - Mortise chisel vs bevel edge chisel | Paul Sellers:https://www.youtube.com/watch?v=q_NXq7_TILA>,.
The Sellers video is interesting. However, I'd be wary of his "need" to have a different method (a different chisel, really) from the traditional. There will be reasons that mortise chisels evolved to the form that they did, whilst bench chisels took a different form.
Despite Sellers claiming words to the effect that that "I trained 3000 woodworkers to use a bench chisel for mortises and none of them ever snapped the chisel" the fact is he can't possibly know this. He can only know it about the short time his students used a bench chisel for mortising under his instruction - unless he has a spy camera in every one of their workshops, which he reviews every day. :-)
But there are some interesting points in the vid.
One is that his bit of glass is taller than the workpiece, Effectively, it's acting as a guide to keep the chisels vertical as they chop. Perhaps when starting out with a mortise chisel, anyone will benefit from this "training aid" (a fence along one side of the marked-out mortise) until they have the feel of the chisel and can keep it vertical by eye and feel?
Another concerns the smoothness of the mortise wall. Sellers indicates that the bench chisel approach gives a smoother wall. This may be because the side edges of a bench chisel have a sharper profile than those of a mortise chisel, because the slope from face to side of the chisel is much less than 90 or 85 degrees of a mortise chisel.
That underlines that the side corners of a mortise chisel (face to side corners) need to be sharpened to a degree allowing them to cut the wall as the chisel moves back and down. Very few how-to vids or magazine articles mention this.
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Some mortise chisels come with 90 degree sides (to the face) rather than being trapezoid in cross-section. A square blade is said to help in keeping the mortise square, as the chisel sides register off the already cut mortise walls, keeping the chisel aligned.
But that can interfere with the cutting action of the corners on the mortise wall; and can even jam the chisel, especially if the side of the chisel has even the slightest of bulges.
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What a lot to think on with mortising with a chisel, eh? :-)
Lataxe
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