Workbench top is starting to come apart

[Bryan Hunt]

I've recently noticed that my workbench top is starting to separate at a couple of the glue joints. The top is constructed of 8/4 x 5" hard maple such that the edges are up and the faces are glued. Should I try to do anything about this before it gets worse?

[harry strasil]

I fixed an old bench out of a school that had that problem by boring a large shallow flat bottom recess with a spade bit then boring a hole all the way thru and putting another recess where it came out. Then marked and cut a piece of all thread the right length and using washers and self locking nuts to pull it together. I made a long narrow sealed box of scraps with weather stripping along the top edge and a hole for my shop vac hose, then wedged the box under the top and turned on the shop vac and put glue on the top of the crack and let the vac suck it into the crack. after the glue was pulled in I tightened up the nuts and finished by driving in plugs so they could be removed if need be.

Jr.

[Ben Grunow]

Could route out some channels and fill with maple dutchmen. Drill a hole across the top and thru bolt with threaded rod. Cut joints out with circular saw and fill with saw blade width dutchmen. THinking out loud.

[Brian Dormer]

Maple moves around quite a bit with temperature and humidity - and if I'm reading this right - you have 5" face-grain to face-grain joints, that is probably what's causing the glue separation. The wood is going to move across the face grain more than in length. You could try getting some glue down into the cracks with a syringe and clamp everything up overnight, but it's probably going to continue to fail at other joints AND you'll have dried glue in the joint getting in your way. That is probably a losing proposition - but if you want to try to avoid the all-thread, you probably won't make it any worse by trying. If you want to keep the top as is: Thru bolting the top with all-thread (as others have suggested) is probably the best option with the least (relatively speaking) work. And try to keep the temperature and humidity in your shop as stable as possible to minimize wood movement. If you don't mind a lot of work: Cut the top apart at the glue lines, joint and plane it down to something like 1.75" x 2" (still beefy, but closer to what you usually see in a maple slab - and less wood movement) and glue it back together. You avoid the all-thread and you'll get enough wood to make almost TWO slabs that size.

[John Thompson]

Whoa... the glue joints are separating on face glueing 5" stock face to face. Rodding it as mentioned or I would simply fill the gaps with glue and re-clamp as looks should not be an issue with a work-bench. If that doesn't stop the problem.. a new top may be in order.

But... I have buiilt over 20 work-benches for myself and friends over a 36 year period. All were at least 3" deep and most around 4". Always face glued them and have never had or heard from recipients of a probelm with separating.... ?

I do not spare clamp pressure (and you can't with 8/4 stock as you used.. I generally use 6/4) and I do check for glue expiration dates on the Tite-bond I use. I personally believe glue expirations do mean something as say expirations dates on beer. I worked for Anneheiser-Bucsh long ago and know that the yeast will separate from the water in beer over 90 days old and I suspect something similar will happen to the bonding agent in wood glues. I don't take chances that are not necessary.

Just wonder if too little clamp pressure.. uneven spread or out of date glue could have been the culprit? When I do a final glue up on a top... I start with no more than 3 strips of stock to ensure I get a proper spread and plenty of clamp pressure before the glue starts setting. I just add strips as the former clamped ones dry. And again.. it miust be fresh glue to satisfy me personally.

Good luck...

Sarge..

[Brian Dormer]

Hmmmm.... I ASSUMED (and we know what ASSuMEd means) that:

The glue was fresh.

Glue was Applied properly (complete coating on both mating surfaces)

AND - Clamped nice and tight at least overnight (a full 24 hours is even better)

If that's not the case, then maybe there's the problem....

You shouldn't NEED to clean the wood with acetone before gluing - Maple doesn't have that much oil in it. Ipe or teak - different story.

ANOTHER THOUGHT - was clamping pressure used to take the bow out of some pieces? They should have been jointed flat prior to glue-up. Although 8/4 anything (let alone Maple) doesn't bend much - even with uber-clamping.

[Bryan Hunt]

Thanks everyone for the suggestions. The top was laminated one board at a time and I cranked down the pipe clamps as tight as I could get them. Both faces were flat and the glue was spread on both faces with a roller. The clamps were left on typically 12 - 24 hours. In retrospect, I did not check the expiration date on the glue so that could be one problem. I probably didn't use enough clamps, so that could be another problem. I definitely have issues with temperature and humidity (my workshop is in the garage) as anyone in the area knows that during the "Winter" you can turn on your heater one day and the air conditioner the next.

To hold it together with threaded rod, I would bore a hole through the center from the face through to the tool tray and bolt it together in three or four places? Is that the idea?

A couple of questions for future reference: Do you sand the faces before gluing? Do you use biskets to keep the boards from moving when applying the clamps, or use clamps top to bottom?

[George Bregar]

Wood movement should not be an issue as grain orientation is the same and it's only 5". It takes a lot of clamp pressure, you should use a caul.

You could rip the top along the failed joint, joint, and reglue. You can route and use a spline to keep flush...too much play in biscuits. Gain, a caul can also be used across the top (width) to keep flush also. Make sure to use wax paper under it.