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I've watched a couple of videos of making mortises.

What technique should I use to remove (bulk) waste from the hole without damaging the ends of the mortise hole? Clearly levering against them will bruise or dent the wood. I'm really looking for a technique which allows me to reliably clear the debris without risking damage. I'm especially looking for answers more specific than "be careful".

Edit: I'm not talking about the paring stage, I'm talking about bulk waste removal.

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First, as Aloysius says above, you should stay away from the ends of the mortise during bulk removal. 1/16 of an inch or 1-2mm should be sufficient.

Now, when you have done a bunch of chopping, and you have chips clogging the mortise, you need to clear them out, as you said. Use a bench chisel that is one "size" below your mortising chisel. For example, a 1/4 inch if you are doing a 3/8 inch mortise. Guide the chisel with the thumb and forefinger of your non-dominant hand as you work it into the chips. Then, still lightly pinching the chisel, rest your non-dominant forefinger on the board and use it as fulcrum as you lever the waste out of the hole. The chisel should not touch the end of the mortise if you do this correctly.

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  • "stay away from the ends of the mortise during bulk removal" -- can we push this further and do it during the entire process. I.e. Could one also give themselves room for error by mortising a slightly shorter mortise than the final length (say 1/16th short), and then paring down the end walls to get them to the marked lines? – ww_init_js Jun 5 '18 at 4:51
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Don't lever. Pare straight downward into the opening, taking it in multiple passes if necessary, and letting the chisel act as a wedge to do the work.

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    Use sharp chisels and sneak up on the cut line. (In other words, do the main cutting about 1/16th off the true line and when that's done, pare the remainder.) – Aloysius Defenestrate Sep 27 '16 at 12:52
  • This answer leaves out the key thing I'm trying to ask about. If you chisel straight down, sure you cut the fibres within the to-be hole. But the waste doesn't magically jump out of the hole, you have to get it out somehow. So how do you do that without damaging the ends of the hole? – James Youngman Sep 27 '16 at 15:10
  • If you take things cuts, the waste pips free at the end if each cut without your having to apply much force. If it doesn't, a diagonal cut into the back corner should free it. – keshlam Sep 27 '16 at 17:53
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Paul Sellers is a master craftsman, author of several books and some very good video tutorials. He does several on cutting mortises - this one probably being most relevant to this topic.

https://www.youtube.com/watch?v=LPBkO2chZxk

I've learned a lot from watching his videos, still dont have the skill to implement the lessons very well as yet - very much a novice at this.

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    I'm a fan of his work too. – James Youngman Sep 29 '16 at 9:44
  • This video was super helpful to me. He does 1/2 the mortise and has it setup so you can see how it's cut. youtube.com/watch?v=q_NXq7_TILA – Dano0430 Sep 29 '16 at 20:31
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    All this answer says is go look somewhere else. While this might be a link to the answer it is better if the content of the answer was here and that the video would help supplement it. – Matt Sep 30 '16 at 2:41
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Are you looking to use only hand tools?

If you have a router, this can get the majority of the mortise bottom flat with a flat bottom bit. Then the corners will be easier to chisel out.

A drill with a forstner bit can be used to accomplish this as well.

If you have a drill press, that would be ideal. There are also hollow chisel mortising attachments you can buy for drill presses that will make perfectly square mortises, and many woodoworkers will "drag" this along the bottom to achieve a relatively flat mortise bottom.

If you want to use only hand tools, a router plane would be capable of achieving this, coming from both directions to get into the corners.

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    It's also possible to use a feeling jig to drill out most of the waste. In fact, there's on jig which will do dowels, mortises (with some chisel work, but it has a guide that helps), or a sort of hybrid loose-tenion joint (mortise both sides, glue a separate tension piece to connect them)... Interesting alternative to the "domino" mortising machines; I haven't found a review yet. – keshlam Sep 27 '16 at 14:10
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    A feeling jig? I haven't heard of that. Do you have a link? – Jacob Edmond Sep 27 '16 at 14:17
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    I'd be interested in that jig, too! – Katie Kilian Sep 27 '16 at 14:42
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    Also, if you want to use hand tools, mortising chisels are made for the job. My understanding is you DO lever with those, but mostly as a technique for clearing out the bulk of the waste, NOT for paring up to the line, which you still have to do to get a tight fit. – Katie Kilian Sep 27 '16 at 14:44
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    Argggh. Doweling jig. Mumble mutter touchscreen keyboards. – keshlam Sep 27 '16 at 17:56
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Borrowing from my own answer about this very topic:

Auger Bits

Whether you are going for traditional techniques or powered/hand hybrid auger bits would be a tool of choice for this.

Using auger bits that are the exact width of you hole you are trying to make, in a brace and bit or drill, you can easily remove waste and not have to worry about going "outside the lines". Stagger the holes and you will get a similar shape like that of the ones you have pictured.

Mortise in progress

From Chris' Project Page

As you can see from the above image (mortise in a workbench) most of the wood was removed with auger bit. The screw tip and the shape help to naturally create straight holes.

I'm really looking for a technique which allows me to reliably clear the debris without risking damage

Be careful when/if you are exiting out the other side. To mitigate damage you can

  • Used waste/scrap wood (clamp well)
  • Count the rotations it takes until the screw (eye) just shows proud on the other side (A Roy Underhill suggestion).
  • Mark the depth of your bits using masking tape.
  • Feel for the screw/eye coming out

Most of those suggestions will work in tandem. This way you can turn the work over and have cleaner edges on the outside.

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