Workbench Top Delaminating

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  • #701374
    Ryan Bailey
    Participant

    Hi All, I just noticed my bench top is delaminating. Any suggestions on the fix? Reglue assembled or dismantle and rip and reglue? Others?

    Maybe things were assembled too tightly or maybe the glue was too light on these prices. The moisture in my basement might also be pretty high.

    #701403
    Jonas Ericson
    Participant

    You should live with this top for many years, so it’s worth putting some effort to it – so I’d say rip it apart. If you try to reglue just the cracks you may have new delaminatings at other parts in some time. To avoid any moisture problems, use epoxi – it lasts at least 20-30 years in boats, and I hope your workshop is slightly less moist than a boat. It is also very forgiving towards unevenness and small gaps.

    #701442
    Colin Scowen
    Participant

    Does it close back up when you clamp it? If so, you might want to try getting a long shaving, slather it in glue on both sides, slide it up in to the gap, and then clamp it closed.

    Colin, Czech Rep.

    #701448
    Larry Geib
    Participant

    If you used PVA I wouldn’t try just squirting more glue in the joint, or using epoxy. Neither sticks to dried PVA well. If you used hide glue, just quiet more glue in the joint and clamp.

    There are a some approaches to consider, depending of your willingness o fuss around, probably in defending order.

    1) add dovetail keys across the joint every foot or so, then just fill the joint with any filler of your choice, from wood strips to any paste filler. The keys will prevent further movement. The keys look kind of cool. George Nakashima used to make and sell slab tops with keys all over them.

    2) rip down the length of the bad joints, plane and edge joint them , planing off the old glue, and reglue the joint. This is about the same work as the keys, but you won’t be able to tell there was a repair, other than a slightly narrower bench top. I just redid a top of a 75 yo table last year and after refinishing, the repair was not noticeable.
    Take extra care this time to make sure you have a tight joint. The wood has cured more, so a repair should last a very long time. My glued up top is over 40 years ond without any sign of delaminations, but I used pretty dried wood.

    I see two joints you would have to do that to, or just redo one joint and add keys to the one that isn’t separated along the whole length.

    3) add a few lag screws through the side of the bench to close or stabilize the joint. Predrill slightly smaller holes for the screws. countersink the heads so they are out of the way and move on. It’s a bench, not furniture.

    4) if the top doesn’t move when you work, do nothing. Lots of bench tops are made in several parts, including Paul’s center well bench circa 2012..

    #701487
    Ryan Bailey
    Participant

    Thanks for the replies!

    I’m leaning toward disassembling, ripping down the length and reglue for the larger opening. I used titebond originally so I doubt anything would stick. For the smaller, I might try the dovetail key.

    Hopefully I can get it finished without having to remake the wellboard. I think it was a little tight originally.

    #702737
    Ryan Bailey
    Participant

    I’m just about ready to tackle this. On question is if I rip and reglue and then if need to reflatten the underside how will I do that with the apron attached?

    #702759
    Larry Geib
    Participant

    It probably won’t be necessary, but if it is, just unbolt the top from the legs, turn the top upside down and plane away. The apron is only on one side.

    Just be careful getting the edge joint square and the pieces flush when you clamp and you’ll be fine.

    #702760
    Ryan Bailey
    Participant

    Looking at this now and thinking through a few more things:

    I guess if I ripped down the length then removed all glue and jointed the top I could attach the larger half to the bench. I could then work the second part and when it came time to glue up, I could do so directly on the bench to help assure there’s as little movement as possible.

    Separate thought- I clamped the two ends with light duty clamps and the gaps easily closed right up. What if I clamped, inserted the dovetail keys and then unclamped? Wouldn’t this keep the joint closed?

    #702763
    Ryan Bailey
    Participant

    Thanks again, Larry. Missed your reply while I was typing mine. I’ve been reading up on George Nakashima and his work.

    Really having a tough time removing the wellboard. Going to wait until tomorrow when everyone here is awake.

    It probably won’t be necessary, but if it is, just unbolt the top from the legs, turn the top upside down and plane away. The apron is only on one side.

    Just be careful getting the edge joint square and the pieces flush when you clamp and you’ll be fine.

    #702782
    Larry Geib
    Participant

    If you are getting the joint tight when it’s clamped and the top is reasonably flat, go ahead and glue it up. Just make sure the joint is also tight when you look up from underneath. You can add the keys after the glue sets up if the clamping pressure to close the joint wasn’t too high.
    Final flattening of the top side can be when you plane the keys flush.

    You might want to put wax paper or cling wrap or even paper between the top and the leg assemblies so they don’t become fused.

    Good luck.

    • This reply was modified 6 months, 4 weeks ago by Larry Geib.
    #702809
    Ryan Bailey
    Participant

    To clarify, I haven’t taken anything apart yet. All I did was clean the bench off and add a clamp at the ends and 1 in the middle to watch what happened to the gap.

    Larry- are you saying fill the gaps with glue then add keys to prevent future separation?

    #702865
    Larry Geib
    Participant

    No. I thought you had separated the top and planed off the glue as I suggested in my first post. Just putting glue in the joint is not a good repair. PVA (poly VINYL acetate) glue when cured is a plastic. When it dries and the polymer chains cross link not much sticks to it well, including more glue. You have to get down to bare wood before you reglue for a full strength joint. So on the worst joint I see, saw it apart, plane it so there is no glue left and the joint is air tight, then reglue and clamp.

    The joint that only has a little separation can be clamped and the keys inserted to prevent further separation. You can squirt some glue in there, but it won’t do much. Most of the holding power will come from the keys.

    Also PVA is not gap filling. It works best with air tight joints and good clamping pressure. And although it is common practice to clamp for a couple hours, titebond really suggests clamping until the glue has completely cured. When I worked in a shop that usually meant overnight cure at temperatures above 50° F.. You can go a little cooler with titebond III (45°F) but I’ve never tried it.

    With overnight clamping we never had a joint failure. Ever. My bench was laminated with Titebond II when it was still in the field trial phase 40+ years ago. Every joint is as tight as the day I put it in clamps. We used my bench because we didn’t want to risk failure with a client’s product..

    I noticed in your first post you were concerned you clamped too tight (you can’t clamp too tight with PVA.) the way to tell you have enough glue in a joint it that a small amount will bead evenly along the whole joint. If some parts don’t bead out, the joint could be glue starved. If you get the amount right, you get a bead that can be cleaned off with a putty knife or cabinet scraper when it is partially cured- say a couple of hours. Don’t try to scrape or wash wet glue off, it just forces glue in the pores of the wood which will lead to finishing problems later.

    • This reply was modified 6 months, 4 weeks ago by Larry Geib.
    • This reply was modified 6 months, 4 weeks ago by Larry Geib.
    #703323
    Ryan Bailey
    Participant

    Thanks for the detailed response, Larry. I have the two pieces ready to glue back together. Would you glue on the bench or upside down on sawhorses?

    #703399
    Larry Geib
    Participant

    I’d glue right on the bench. That will tell you if the top is jointed right and will lay flat without stressing the joint. Make sure the leg cross stretchers are both level.

    And put something between the top and the stretchers so you don’t glue them together. Wax paper, plastic film, or even newspaper will work.

    #703861
    Ryan Bailey
    Participant

    The top is glued and back on the bench. I ended up adding an additional board since it was just sitting here and the wider top would allow me to correct my out of square rebates on the original wellboard. I still need to flatten further but it’s pretty close. In the middle there is a section that is low along the new joint but it’s not a big deal. Im going to add the dovetail keys and a planing stop to the top then do the final flattening.

    Also, when I separated the top, I found that there was still an old finish on one half. I wonder if that was actually supposed to be an outside board as it had some writing on it too. This leads me to believe that I made a mistake during the original glue up. Either way, I can see why the glue didn’t hold. Thanks again for the help!

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