Workbench Top Delaminating

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.

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..

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 2 years, 3 months ago by Larry Geib.

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 2 years, 3 months ago by Larry Geib.
• This reply was modified 2 years, 3 months ago by Larry Geib.

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.