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Thread: Chopping Mortises

  1. #1
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    Chopping Mortises

    I'm currently working on my bench and chopping mortises for the stretchers in the legs. Using laminated SPF 2x4s and a 12mm bevel edge chisel.
    I do not own any mortise chisels. No drill press. No auger bits. So I'm asking for any tips on chopping better mortises.
    The chisel is square, with a 25 degree primary bevel and an approximately 30 degree micro bevel.
    I seem to wander a bit as I go, and my walls are a bit out of square. Is this just a matter of getting better with practice, or are there any tricks or techniques that are greatly beneficial?

    Thanks.

  2. #2
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    Hey Nathan,

    Here's a tip that helped me a lot. Mark out all four sides of your mortise with a marking gauge and knife, and then use your knife to score all four sides deeply. Use a chisel the exact same size (or if you can't, smaller) to peel out the wood in between the marks. If you scored them deeply, in pine, you should have around 1/16 to 1/8 shallow 'mortise' that you can now use to register your chisel for all the cuts you'll be making. It'll give you much cleaner side walls compared to the inevitable variation in chisel placement that happens when you're cutting your first mortises. I've seen this method used in a number of places, such as Derek's website.

    A lot of folks prefer drilling out the mortise and then finishing up with a chisel but I find that cumbersome and less accurate. The best way (for me) is to size my mortise exactly the width of the chisel I'll be using and chop away.
    Last edited by Hasin Haroon; 08-11-2017 at 11:48 AM.

  3. #3
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    Quote Originally Posted by Hasin Haroon View Post
    Hey Nathan,

    Here's a tip that helped me a lot. Mark out all four sides of your mortise with a marking gauge and knife, and then use your knife to score all four sides deeply. Use a chisel the exact same size (or if you can't, smaller) to peel out the wood in between the marks. If you scored them deeply, in pine, you should have around 1/16 to 1/8 shallow 'mortise' that you can now use to register your chisel for all the cuts you'll be making. It'll give you much cleaner side walls compared to the inevitable variation in chisel placement that happens when you're cutting your first mortises.

    A lot of folks prefer drilling out the mortise and then finishing up with a chisel but I find that cumbersome and less accurate. The best way (for me) is to size my mortise exactly the width of the chisel I'll be using and chop away.
    Thanks. I am using a mortise gauge (well, the Veritas dual marking gauge) set to the width of the chisel I'm using, but just using the gauge lines. I'll try making those deeper and see if that helps.

  4. #4
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    Hi Nathan,
    Along with what Hasin said I use 1/8 thick x 1 or 1.5 inch aluminum angle to register the chisel against to maintain a vertical wall. Being an angle ii's easy to clamp to the board. I have several different lengths of angle and use the length appropriate for the board. Good luck with your project.
    Chet

  5. #5
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    Paul Sellers has a Youtube video on chopping mortises. I found it very helpful, and for whatever reason when I do it that way they end up square.

  6. #6
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    Quote Originally Posted by Chet R Parks View Post
    Hi Nathan,
    Along with what Hasin said I use 1/8 thick x 1 or 1.5 inch aluminum angle to register the chisel against to maintain a vertical wall. Being an angle ii's easy to clamp to the board. I have several different lengths of angle and use the length appropriate for the board. Good luck with your project.
    Chet
    Good tip, I can try that. Thanks.

    Quote Originally Posted by Nicholas Lawrence View Post
    Paul Sellers has a Youtube video on chopping mortises. I found it very helpful, and for whatever reason when I do it that way they end up square.
    Yes, his method is what I am trying to emulate. Sure looks easy when he does it.

  7. #7
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    Sounds like these may be your first or at least "firster" mortises and , if so, yes it will get better as you gain experience. In my opinion, the Paul Sellers demo is one very definite way to chop them with good results. Work bench frame mortises are usually large and deep, so the joint will be solid if some small area of the entire mortise is slightly out of plumb due to minor undercutting. I run a small square along the side and end walls of the mortise to check for any "bulges" that will prevent the tennon from sliding in and tend to skip using a square guide to hold my chisel against because I don't have too much trouble ending up plumb. Certainly a wider chisel helps create a more consistent sidewall, but the 1/2" - 12mm size chisel is probably my most used paring chisel. If the wood is hard, a 35* micro bevel may be better, but that is for you to decide. If the $ is available, maybe order a wider chisel for use here and to add to the collection. Also, I don't tend to pound the chisel for maximum penetration when chopping, but just bop it a couple of whacks to take what the chisel gives me. That tends to keep my chisel better in square than when I try to go for deeper penetration by pounding harder.
    Last edited by David Eisenhauer; 08-11-2017 at 2:08 PM.
    David

  8. #8
    A guide block will be of great help to you.

    Its not hard to ruin a bevel edge chisel chopping mortises. A firmer chisel will be more expeditious. Any fairly decent utility chisel will do, then use your bevel edge to fine tune the sides in conjuction with the guide block.

  9. #9
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    I attended Homestead Heritage when Paul Sellers was there, we learned to chop mortises with bevel edge chisels.
    You just don't pry out large chips. Try it, it works. I have mortise chisels and use them, but occasionally on a small
    mortise, I will use a bevel edge chisel, especially on 1/4" mortises.
    Last edited by lowell holmes; 08-11-2017 at 3:13 PM.

  10. #10
    Pay attention to these three things, too:

    - take care to place the chisel so the cutting edge is right inside the scribed lines when you start, Close enough is not good enough as long as either edge corner cuts outside a line
    - chop perpendicularly which is easier said than done unless you position yourself properly so can see you are chopping plumb. Practice and have someone stand in front to tell you if you are indeed chopping plumb. Thinking that you are plumb with the chisel does not cut it. Set up a mirror if no one can help you.
    - when you pry, make sure you pry straight and not slanted, but parallel to the walls. Key word: take it slow till your muscle memory takes over.

    If you rush before you are good at it, you are bound to get crappy or bruised mortises. Gappy joint? Don't listen to the videos where you see the guy fill the gap with sawdust. It does not work and will only fool a non-woodworker. Once you apply a finish to the piece, the fix will pop up.

    Mortise and tenon is a good joint for using your chopping as well as sawing skills. Worth the time to become very very good at it. Remember: mortises first, though I have seen books showing cutting the tenons first.

    Simon
    Last edited by Simon MacGowen; 08-11-2017 at 6:30 PM.

  11. #11
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    Quote Originally Posted by David Eisenhauer View Post
    Sounds like these may be your first or at least "firster" mortises and , if so, yes it will get better as you gain experience. In my opinion, the Paul Sellers demo is one very definite way to chop them with good results. Work bench frame mortises are usually large and deep, so the joint will be solid if some small area of the entire mortise is slightly out of plumb due to minor undercutting. I run a small square along the side and end walls of the mortise to check for any "bulges" that will prevent the tennon from sliding in and tend to skip using a square guide to hold my chisel against because I don't have too much trouble ending up plumb. Certainly a wider chisel helps create a more consistent sidewall, but the 1/2" - 12mm size chisel is probably my most used paring chisel. If the wood is hard, a 35* micro bevel may be better, but that is for you to decide. If the $ is available, maybe order a wider chisel for use here and to add to the collection. Also, I don't tend to pound the chisel for maximum penetration when chopping, but just bop it a couple of whacks to take what the chisel gives me. That tends to keep my chisel better in square than when I try to go for deeper penetration by pounding harder.
    Thanks for the detailed reply.
    Yes, these are my first mortises, other than testing on a couple of scrap pieces. I'm brand new to woodworking really, and this bench is my first project.
    12mm was the closest I could get to making the tenons 1/3 the width of the stretchers. I might try playing with the bevel angle...

  12. #12
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    Quote Originally Posted by Simon MacGowen View Post
    Pay attention to these three things, too:

    - take care to place the chisel so the cutting edge is right inside the scribed lines when you start, Close enough is not good enough as long as either edge corner cuts outside a line
    - chop perpendicularly which is easier said than done unless you position yourself properly so can see you are chopping plumb. Practice and have someone stand in front to tell you if you are indeed chopping plumb. Thinking that you are plumb with the chisel does not cut it. Set up a mirror if no one can help you.
    - when you pry, make sure you pry straight and not slanted, but parallel to the walls. Key word: take it slow till your muscle memory takes over.

    If you rush before you are good at it, you are bound to get crappy or bruised mortises. Gappy joint? Don't listen to the videos where you see the guy fill the gap with sawdust. It does not work and will only fool a non-woodworker. Once you apply a finish to the piece, the fix will pop up.

    Mortise and tenon is a good joint for using your chopping as well as sawing skills. Worth the time to become very very good at it. Remember: mortises first, though I have seen books showing cutting the tenons first.

    Simon
    Thank you. And apologies for my cantankerous replies the other day.
    The mirror idea is good.
    And yes, I am cutting the mortises first and then fitting the tenons.

  13. #13
    [QUOTE=Nathan Johnson;2716368]Thank you./QUOTE]

    No hard feelings at all as we all are just trying to put our points across. Once a thread is over, any disagreements are over too.

    Good luck with your mortise & tenon attempt. It really is a cornerstone of furniture joint. In some ways, it (through m.t.) is more demanding that a through dovetail joint.

    Simon

  14. #14
    Quote Originally Posted by David Eisenhauer View Post
    Sounds like these may be your first or at least "firster" mortises and , if so, yes it will get better as you gain experience. In my opinion, the Paul Sellers demo is one very definite way to chop them with good results. Work bench frame mortises are usually large and deep, so the joint will be solid if some small area of the entire mortise is slightly out of plumb due to minor undercutting. I run a small square along the side and end walls of the mortise to check for any "bulges" that will prevent the tennon from sliding in and tend to skip using a square guide to hold my chisel against because I don't have too much trouble ending up plumb. Certainly a wider chisel helps create a more consistent sidewall, but the 1/2" - 12mm size chisel is probably my most used paring chisel. If the wood is hard, a 35* micro bevel may be better, but that is for you to decide. If the $ is available, maybe order a wider chisel for use here and to add to the collection. Also, I don't tend to pound the chisel for maximum penetration when chopping, but just bop it a couple of whacks to take what the chisel gives me. That tends to keep my chisel better in square than when I try to go for deeper penetration by pounding harder.
    David,

    The best advice of the bunch. This is a case of slower is faster, less is more. Bench or pig sticker it should be tap, tap, lever, tap, tap, lever, repeat till finished. Going Conan makes for a bad mortise and will slow the process.

    ken

  15. #15
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    Just to echo what others are saying, it is like learning many tasks in life, work toward accuracy and speed will come naturally with time.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

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