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How to fix a mortise and tenon angle?

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This topic contains 4 replies, has 4 voices, and was last updated by  kevinjames 1 year, 8 months ago.

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  • #410140

    Dave C
    Participant

    I’ve been having a go at the small table project from this site, have cut all my mortises and tenons, and just fitting them now.

    One (major?) problem so far is that although the mortise and tenon fit well together, the apron now isn’t at 90 degrees to the leg, so I can’t see how the table will ever end up being square.

    The fit of the mortise and tenon is pretty loose, so I don’t know how to fix this by removing any more material.

    Any advice or suggestions? I’m not even sure how to work out why/where the angle is being caused. Both pieces of wood are dead square, no bowing or twisting, it definitely seems to be the joint itself.

    When the tenon is fully seated, the gap at the front of the table is closed, but there’s a big gap at the back.

    All I can think of is to glue some wood into the mortise sides, then try to fit the tenons to those, no idea if it would work though.

    I’ve attached a photo to show what I mean, in case it helps.

    Attachments:
    #410518

    SmokyRick Crawford
    Participant

    When you have it fully seated and there is a gap at the back but not at the front, is it square then? If not, then maybe you need to shave a little off the back of the tenon to allow it to sit straight. That is all I can come up with right now.

    In the middle of Northern Illinois, USA

    #410582

    Dave C
    Participant

    [quote quote=410518]When you have it fully seated and there is a gap at the back but not at the front, is it square then? If not, then maybe you need to shave a little off the back of the tenon to allow it to sit straight. That is all I can come up with right now.[/quote]

    Unfortunately not – when it’s fully seated, there’s a gap at the back but not front, but it’s still out of square there.

    All I can think is that maybe the mortise was cut at a very slight angle rather than being 90 degrees down?

    #412198

    deanbecker
    Participant

    Verify the tenon is coplaner with the side of the skirt and then verify the mortice is verticle in the leg. If you have a router you can make a guide to pare the mortice sides or look closely and you can see if the mortice is out of square.
    It appears in the picture that the bottom of the mortice is further from the edge of the leg than the top. This would open the back of the joint when the tenon was installed.
    Also how loose are your tenons.

    #478531

    kevinjames
    Participant

    Having a slight gap on the inside is really not terrible. It might not be “perfect”, but that could actually help in the long run. Because your aprons will be slightly out of square, forcing them all together will add tension to the frame and add strength. The English Woodworker just addressed this very issue recently (you can find him online under that name). Christopher Schwartz also just addressed this issue as it relates to chair building. The same principle applies. Slightly our of whack joints add strength because they will be under tension when you make them square.

    As long as you can get everything square with clamps and such, you’ll also have the tabletop to help keep it right where you want it once its secured with the buttons.

    If you’d rather have everything all nice and tidy, you can make your mortise slightly larger by paring the side that’s not allowing it to straighten out to 90 degrees, then glue a small strip of wood to your tenon, and re-pare the tenon down to fit. If your tenon ends up being slightly loose, drawbore pinning them will help.

    I’ve had this same issue and it all seemed to work out for me.

    Good luck. Kevin

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