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Mortice and Tenon problem

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Viewing 6 posts - 1 through 6 (of 6 total)
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  • #58671
    BondiMacF
    Participant

    Hello my friends,

    I am making slow progress with my workbench, but better slow than not at all.

    I’m using recycled timber for this, essentially my old decking which I wanted to re-purpose. There are the 2×4 beams, and the actual decking planks. (you can see some of it in the photos). I like the sustainability of recycling stuff…

    I’m just coming to checking the fit of the H-frames and to my (not so great) surprise find that it’s all off. In fact I can probably count the mortices and tenons I have cut in my life on two hands and two feet. so not a lot. I’m hoping that with practice this will get better.

    The bottom beam seems to fit in quite nicely (I haven’t done the round overs yet), but on closer inspection (picture 2) the upright seems to be rotated clockwise a few degrees.

    In picture 3 you can see how badly it’s off. I suspect that the bottom left tenon isn’t straight or maybe the leg is twisted.

    Would you suggest I cut the tenon on the top rail into a triangle shaped wedge so it will fit, or keep the tenon at its current width and open up the mortice into a wedge shape to take the tenon diagonally, and then secure it with a wedge for the outside? It’ll be behind the apron so not visible. I wonder if the first idea might actually weaken the tenon by making it smaller and taper to a point at the tip.

    All that remains now is to work out where I went wrong and how to make sure I stay straight on all joints on the next h-frame.

    Thank you so much in advance.

    Ipswich, Suffolk, United Kingdom

    Attachments:
    #58675
    BondiMacF
    Participant

    pictures 2 and 3

    Ipswich, Suffolk, United Kingdom

    Attachments:
    #58680
    David Payton
    Participant

    I would also suspect a bit of a twist in your leg. This is stock that has had a prior “career”, so to speak, as outdoor deck parts.

    My suggestion would be to form your tenons to fit your mortises properly at each end. Keep track of which tenon fits which mortise, fit both tenons into one leg, and carefully start the opposite ends into the mortises. See if you can force the twist out enough to bring your tenons through. Be patient and persistent. It appears that you are employing haunched tenons. This should help keep things square once you get them together and tight.

    Good Luck,
    Dave

    #58682
    Greg Merritt
    Participant

    It looks like you have three lines marking out this mortise and that you lined your chisel up on a different line when you flipped the leg over. The mortise clearly changes direction about half way thru the leg. Measure from the face side of the leg to the edge of the mortise. I bet that will tell you what the problem is.
    As to how to fix it.

    Option #1-Make a new leg if you have the material.

    Option #2-Square up the mortise so that the tenon seats squarely thru the leg. Then create a wedge to fill the gap. Plenty of glue during assembly.

    This looks to be pressure treated lumber. Please be careful. There are lots of nasty chemicals in pressure treated lumber. These chemicals can get into your system thru direct contact and off gassing. You may want to do a little research on it. Your an adult and can make your own decisions, just make an informed one.

    http://hillbillydaiku.com

    #58686
    BrianJ
    Participant

    Also try sighting down the pieces to see any twist, winding sticks might be of help to and the do not have be fancy to start. I agree with the layout should be double-checked as well. Brian

    Ontario, Canada

    #58703
    BondiMacF
    Participant

    Hi Guys,

    Really good advice there. Thank you.

    Also, Greg, I do believe they are pressure treated. They’ve been pretty indestructible, and have sat around in the snow, wind, sun and rain, and haven’t split or rotted for years.

    I had no idea that the chemicals in the wood were that bad. I’ll definitely be more careful – thank you.

    Will make sure not to breathe in the sawdust, and not put shavings in the compost any more.

    Thank you for point this out.

    I’ve got a very good saw mill a couple of miles from here, so will be getting decent wood after this project is done.

    Ipswich, Suffolk, United Kingdom

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