Workbench Leg Repair

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This topic contains 16 replies, has 5 voices, and was last updated by Robert DeMarco Robert DeMarco 5 months ago.

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  • #7845
    Bill Leonhardt
    Bill Leonhardt
    Participant

    I am in the process of building the workbench in the photo. Each leg is made from two pieces glued together. The inner part of the leg has two mortises for the upper and lower end stretchers. The tenons in the stretchers are slotted and when the stretchers are assembled into the inner legs, wedges are driven into the tenons. Well, 3 out of 4 legs are just fine, but I guess I got a little too enthusiastic with the forth. Cracked the leg.

    Details of the crack and my proposed repair are detailed on the attached file. Comments, please.

    Thanks,

    Bill

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  • #7848
    Michael Luciano
    Michael Luciano
    Participant

    Is it possible to use a small diameter drill bit to drill holes along the wedge? This would allow the gap to close and you could get glue, or epoxy, into the wedge, or gap that results.
    Might be easier then trying to route that deep.

  • #7849
    Bill Leonhardt
    Bill Leonhardt
    Participant

    Mike,

    Good suggestion. I could try the drill bit approach first and, if that didn’t work, default to the router.

    Bill

  • #7852
    Avatar
    Charlie James
    Participant

    Bill, It’s tough when you’re glueing so close to the edge. I’m not sure whether you’re repairing the crack for looks or strength? You can always drill and set dowels (not too large, you’ll want more smaller ones) into the leg horizontally across the crack.As many as you feel comfortable with, the whole leg if you want. Glue and clamp the leg. You can drill holes for dowels and glue them in right away, that’ll hold it permanently. Ask me how I know this works!!

  • #7853
    Bill Leonhardt
    Bill Leonhardt
    Participant

    Thank Charlie,

    I wasn’t so worried about strength, but belt & suspenders ain’t bad. Perhaps a couple of dowels.

    Bill

  • #7854
    Avatar
    Charlie James
    Participant

    I didn’t fully comprehend (or read your page!) but I see you made the crack wider. You can fill that with a piece of ash ripped on your bandsaw, then glue & clamp. While it’s clamped drill holes for dowels all the way through the leg (B). Then put yellow glue in the dowel holes and send them in so they’re sticking out on both ends, you’ll cut them off later. I would guess that anywhere from 4-6, 3/8″ Diameter dowels about 6″ long staggered down the leg (and not too close to the edge). Drilling for larger diameter might take away too much meat from the leg.You would know the size dowels that would work best, better than me. Once it’s dry you can plane the edge of the leg as you see fit as the repair will be permanent and strong, if not stronger than before. If you’re concerned about the other legs splitting as time goes on due to stress you can use this same treatment without a problem right away while you have all the tools in place and the wood’s easy to work on. You can put some dowels from back to front as well, all the way through the back piece and half way through the front. Ash has a tendency to split along the grain, much easier than most other hardwoods. It’s a nice choice for the bench, plenty of weight

  • #7855
    Bill Leonhardt
    Bill Leonhardt
    Participant

    Charlie,

    I’m a little confused by your last post. Since the inner and outer legs go together “face grain to face grain”, I’m not worried about the strength there. I’m only worried about the strength of the top end stretcher to the inner leg connection. Once I have repaired the crack so that I am comfortable putting the inner and outer legs together, I can either put a couple of dowels (1/4″ or 3/8″) through the inner leg and into the end stretcher tenon perpendicular to the tenon axis or through the outer leg and into the tenon parallel to the end stretcher axis.

    Bill

  • #7856
    Avatar
    Charlie James
    Participant

    Bill, you’re right. It’s to involved…

  • #7857
    Michael Luciano
    Michael Luciano
    Participant

    I think, that the wedging action has to be relieved so the crack can be closed. The crack goes right down the center of the wedge. If you drill down along the wedge line you will remove material and clamping pressure should allow the wood to move bringing the edges together. Gluing the face board on should hold the inner leg in place. The wedge did its job namely moving the wood over to fill the space, too much pressure and the leg split. The wedge split, because the glue on the wedge faces was stronger then the wood. What do you think?

  • #7858
    Bill Leonhardt
    Bill Leonhardt
    Participant

    Mike,

    I agree that material has to be removed to get the leg back to its original width. Drilling down might be enough, but the drill diameter has to be at least the amount the leg width has increased. I will try that, but I suspect I will go the router route in the end. My thought is that once the groove (from the router) is in and the width of the leg can be squeezed to its original dimension with low clamping pressure, I can custom fill the slot with a a piece of wood and epoxy. Afterwards, flush it to the original inner leg surface and then glue on the outer leg.

  • #7861
    Avatar
    Charlie James
    Participant

    Some woodworkers will drill a hole at the head of the wedge cut to relieve pressure. I believe it helps prevent splits so next time if you think of it…

  • #7862
    Bill Leonhardt
    Bill Leonhardt
    Participant

    Charlie,

    I drilled holes in the tenon. It was the mortise that failed.

    Bill

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  • #7864
    Joe Bottigliere
    Joe Bottigliere
    Participant

    Bill,
    I know this comes after the fact and is of little help to you. But anyone else who may consider a similar build or technique should make note of this. Since no one else mentioned it, I think it worth pointing out. You should avoid wedging a tenon such that the forces will be perpendicular to the grain direction. That is, so that it forces the vertical grain apart like an axe. Had your wedges been located horizontally, you would not have split the grain. They could have at least been installed diagonally in the joint and still you could have avoided the split. Of course, that is not always practical and one should consider the location of the mortises. If it is far enough from an edge, or not very deep, the damage will be avoided. But these look pretty close to the edge of leg and they are designed to go all the way through. You did not mention it, but did you relieve the mortise walls to allow room for the displaced tenon or were the mortise walls just cut straight? I believe that also helps to relive the splitting effect of this technique.
    It’s obvious that the other legs were fine. But I think it is worth noting for those less aware of these pitfalls.
    For what it’s worth, my suggestion would be to inject some epoxy into the split and clamp it closed. (Of course do what you must to allow it to clamp closed.) Then reinforce it with dowels as Charlie recommends.
    Good luck!

  • #7865
    Michael Luciano
    Michael Luciano
    Participant

    Bill, I may be flogging a dead horse but…..if you use a drill diameter that is the same as the wedge width at the top, you are essentially removing the wedge. Glue or epoxy into the hole and crack, clamp and put the outer leg on. There wont be any upward force on the joint. A dowel from the inside thru the tenon would not hurt.

  • #7884
    Bill Leonhardt
    Bill Leonhardt
    Participant

    I made the repair.

    I followed Mike’s suggestion by drilling out the wedge. I used a 3/16″ brad point bit. It was a lot easier than I expected. This resulted in a ragged slot that I cleaned up with a 3/16″ mortise chisel and bench chisel. I clamped up the leg to close the crack and assure I could get the leg to almost its original width. I tested my biscuit fit. It was OK.

    I then made a filler piece with a “not-too-tight” fit. I removed the clamp and I wedged open the crack a little so I could put white glue in the crack at the top of the leg, then I clamped down the leg to close the crack. I epoxied in my filler piece and let every thing cure. After curing, I cleaned off the filler piece. I measured the leg width with the clamp on and then with the clamp off. Very little expansion, so I declared this a success. I also checked that I could assemble the outer leg to the inner leg with the biscuits. All was good.

    Thanks to all who commented. Definitely a,learning experience. I attach a file showing the repair.

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  • #7888
    Avatar
    Charlie James
    Participant

    Bill, it worked out very well…

  • #7894
    Robert DeMarco
    Robert DeMarco
    Participant

    Nice job Bill

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