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Thread: Repair missing broken tenon

  1. #1

    Join Date
    Mar 2008
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    Toronto, Ontario
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    Question Repair missing broken tenon

    Hi,
    Can I get some suggestions on how to repair this tenon that was broken and the wood was lost. The tenon will be load bearing since it is attached to the front / focusing standard. The wood appears to be mahogany. I would like to fix this so I will be able to take images with the camera.

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    Any advice would be appreciated.

    Kirk

  2. #2

    Join Date
    Apr 2009
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    Seattle area, WA
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    Re: Repair missing broken tenon

    Well wood glue is just a strong as wood or not stronger. The most straightforward, if not easy, solution seems like to fashion a new piece from mahogany and glue it in place. If you can reinforce it with metal strips.

  3. #3

    Join Date
    Jan 2009
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    Denmark
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    Re: Repair missing broken tenon

    I have done similar repairs. As this is pretty much out of sight, I would remove the rest of the tenor with a plane and sand paper Block.
    Then get hold of a nice “greasy “ piece of something like black walnut - which is not a CITES protected hard wood. Glueing and clamping is difficult, so I would use some attractive brass screws in connection with glueing.

  4. #4

    Re: Repair missing broken tenon

    If you want it repaired once and right I would send it to someone who knows what they are doing.
    I have done more repairs to camera that were repaired by someone who did not know what they were doing or got the wrong advice.

    I was ask the repair cost of a broken part on a camera. At the time the cost would of been $65. The person decided to do it him self and went to the hardware store and ask the clerk what is the best glue to use. He bought the glue never read the direction on the glue bottle. Put glue on both parts and then decided that the best thing to do was to use the camera body to hold all the parts together. Well the glue did its thing and foamed up and glued the rail to the camera body.

    I had to use a chisel and saw to get the camera apart. Final cost of a $65 repair gone bad $350.
    Richard T Ritter
    www.lg4mat.net

  5. #5

    Join Date
    Jul 2006
    Location
    Collinsville, CT USA
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    1,952

    Re: Repair missing broken tenon

    Years ago I acquired a wooden Burke & James Rembrant camera. Cosmetically the camera was in excellent plus condition obviously having seen very little use since it was bought in the mid 1960s. Unfortunately the wood was also broken in several places. An educated guess is that something large fell on it. I called on a friend who restores furniture for advice. He told me first to strip the paint from the wood to be able to closely inspect the broken wood. I did this. He told me to then apply Gorilla glue to one break at a time. First mist the wood in the break several times over the course of an hour. Then apply a little more than just a skim coat of Gorilla glue. Very, very firmly using multiple clamps, clamp the pieces together. Now to remove all the Gorilla glue that seeps out from the break as it cures over the next hour with a common hard plastic joint knife (which will not scratch or harm the surface of the wood). Leave it alone, being clamped for a few days to completely cure. Then proceed to repair the next break. The camera had five or six breaks and it took me probably 2 weeks to totally repair it. For some of the breaks I had to fabricate a jig to be able to clamp the break shut tight. In the end I decided to not repaint the wood with B&J's gray color. Instead I stained it. Repaired breaks were only noticeable upon a very, very close inspection. My friend told me that Gorilla glue was far superior to using any common "wood glue". It was just a lot harder to use, and required a longer curing time which was why most people didn't use it.
    He also told me that drilling and adding on additional brass screws in many cases will further lessen the integrity of the repair unless one knows exactly what they are doing, especially knowing the correct drill size to use with different woods (soft wood - smaller hole, hard wood - larger hole).

  6. #6
    Tracy Storer's Avatar
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    Oakland CA
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    975

    Re: Repair missing broken tenon

    Richard Ritter gives good advice.
    I wouldn't call the broken bit a tenon, rather, what is left of the rail after cutting a rebate (rabbett) in the top.
    If, IF, you are a good woodworker and have good command of your tools and materials, I would say to mill away that "tongue" and about the same amount again from the rail and glue in a whole new continuous strip of mahogany that runs the full length front to back.

    If you don't have the tools and skills to do that and end up with everything being the right width and thickness, find somebody to handle it for you (like RR).
    Tracy Storer
    Mammoth Camera Company tm
    www.mammothcamera.com

  7. #7
    (Shrek)
    Join Date
    Mar 2011
    Location
    Montreal
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    Re: Repair missing broken tenon

    Quote Originally Posted by Tracy Storer View Post
    Richard Ritter gives good advice.
    I wouldn't call the broken bit a tenon, rather, what is left of the rail after cutting a rebate (rabbett) in the top.
    If, IF, you are a good woodworker and have good command of your tools and materials, I would say to mill away that "tongue" and about the same amount again from the rail and glue in a whole new continuous strip of mahogany that runs the full length front to back.

    If you don't have the tools and skills to do that and end up with everything being the right width and thickness, find somebody to handle it for you (like RR).
    I have a project camera somewhere in the pile that has exactly this problem, someone ripped off the front standard, ripping away the outer top part of both rails in the process, and just for good measure they lost the broken pieces. I intend to do exactly this repair. Someday.

  8. #8

    Join Date
    Mar 2008
    Location
    Toronto, Ontario
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    81

    Re: Repair missing broken tenon

    Thanks everyone for their input. I am currently reluctant in repairing that part at the moment. It seems to be delicate work and feels like a low chance of success for my repair skills. As much as I would love to keep all the original parts, I will try my hand at making new pieces / parts on a little cnc router and stain to match. If I can do it, I can transfer the rack if I am successful. If I am not successful, I can send the original part off to get properly repaired.

  9. #9

    Re: Repair missing broken tenon

    You've gotten some truly knowledgeable and well informed replies here. Do heed them. Everything you need is within them.

    This sounds pedantic I admit, but rather than calling it a 'tenon', a tongue, rail, runner or guide would better describe the damaged part. Regardless, I'd remove the whole focusing rectangle assembly, undoing anything that can easily be redone. Set up a router with a straight bit partially buried in a fence at a height and depth that you creep up on in order to remove the entire length and width of the damaged area. Shape a new runner to fit the negative (rebate) that you just created and glue it in. Not really a CNC job but still delicate.

    It is indeed Mahogany and the grain should run left to right, not top to bottom, when you glue that in place.

    I do prefer a slow setting glue for tricky glue ups. Gorilla is not a bad choice since you can easily clean up any foam out. The trick is to not let the squeeze out get fully cured before clean up. Any wood glue will work though. You'll want to clamp both horizontally and vertically at the same time, with gradual clamp tension adjustments to allow it to naturally slide and bottom out in the negative space you routed. Line your cauls with a strong clear packing tape. Check with a straight edge to make sure you're not introducing a slant to the runner. With enough force that's an issue. Be gentle. Even a taped joint would work here. Tape the replacement runner in place on it's widest edge. Fold it open, apply glue, partially close it and open it again, respread the glue evenly and leave it open for 30 seconds to allow the glue to seep in, then tape it shut in several places.

    Glue the new runner on over long and pare it flush after curing if you want perfection. 1/32" extra on each end is enough. Easily chiseled, with a slicing motion, off later.

    I'm so impressed with the responses you have received that I can only hope that mine measures up and offers something too.

    Let us know how you get on.

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