Bench top glue-up problem

Re: Bench top glue-up problem *LINK*

Pam Niedermayer - Austin, TX

>I think you're on the right track, just be sure that whatever method you choose can repress buckling. You might want to check out Alburnam's Archive for some other ideas.


Alburnam's Archive

Re: Bench top glue-up problem

Tom Ryan

>I used threaded rod. I drilled all the boards with holes that lined up. I used 3 threaded rods (for a 5' top), each about 20" long (the width of my bench, excluding the tool tray. I put a few boards on the rod, put on washers and nuts, and tightened. The next night I undid the nuts and washers, and added a few more boards, and so on.

The first and last boards were counterbored for the washer and nut. I left the rods in the bench top, but you could remove them.

An alternative would be to make clamps with threaded rod. Each clamp would have two threaded rods, one above the benchtop and one below. On each end, you would have a short piece of wood with holes for the threaded rods

I like the wedges

Jack Guzman from Maine

>I recently did a glueup that none of my clamps could handle.I placed the items to be glued between the front and back boards of my tablesaw sled,I added a shim to make the fit better and then drove in wedges wherever I thought a clamp should go.You could do something similar with 2x material.Make a frame of two parallel 2x s and cross pieces.Set your bench sections on the cross pieces and wedge them together.I hope this makes sense.---Jack

Re: If you are using....

Dale Lenz-Tahlequah, OK

>pipe clamps. I always have my pipes thread on both end. That way if I need to add extra length I just screw off the pipe clamp head and screw on a pipe couple. Put the pipe head back on the other end and longer clamp.

Good luck,

Dale

P.S. I used the all-thread thingy also, some 20+ years ago.......Dale

Re: Bench top glue-up problem

R.J.Whelan

>Robert,

I have a glue up table the sits on saw horses when in use and against a wall in the shop the rest of the time.

The table is made from a sheet of 1" MDF (it's flat and stable); one fixed 2x4 running along one long edge - glued and screwed in place; another 2x4 that slides back and forth (parallel to the fixed 2x4) in four routed slots and held in position with 1/4-20 bolts, nuts and washers.

In use, as stated at the beginning, the table is laid on saw horses:

1. The sliding 2x4 is positioned 1" wider than the width of the glue up

2. Lay a plastic sheet (disposable) between the two 2x4's to keep the glue-up from sticking to the table

3. Apply glue to all appropriate edges

4. Arrange timbers as desired

5. Wrap excess plastic over the top of the glue up

6. Insert opposing wedges every 8-12" and tap them slightly tight

7. Lay short lengths of 2x4 across the glue up at both ends and (where appropriate) a couple of mid points

8. Run a third 2x4 down the center of the length of the glue up and clamp each end - this forces the panel flat. A slightly crowned 2x4 aids in getting even pressure along the length of the glue-up.

9. Tap the wedges tight

10. Let the glue up cure for whatever time is appropriate.

This is the second iteration of this jig I've built. The wedges exert quite a bit of force on the 2x4's and the glue joint eventually fails. When this happens I just rip off about 1" of the MDF and install a new 2x4. The first version used 3/4 plywood, which wasn't as stable or flat over the long haul. This latest version is five years old and I've rebuilt the fixed edge twice. When brand new I could do a 44" wide glue up - now I'm down to 42".

Tips:

1. Screws don't hold very well in MDF (there are some specialty screws but I've never tried them. I drill a 1/2" hole for each screw and glue in a 3" piece of oak dowel.

2. Poly glue seems to work better than any other adhesive I've tried - possible exception being West System 2-part epoxy.

Good luck with your bench .... rj

Re: Bench top glue-up problem

Pam Niedermayer - Austin, TX

>RJ, seems that if you use tapered wedges in this setup you run the risk of the mdf side of the glued joints being forced slightly out of contact (vs forced into contact on the top where the wedge is thickest).

Pam

Re: Bench top glue-up problem

R.J.Whelan

>Pam,

Not sure I understand what you're saying; each pair of wedges have their bearing surfaces parallel to the glue up and to the moveable part of the table.

The table works really well and I get dead flat glue ups ... rj

PS ... maybe my description lacked clarity ....

For want of a nail

Adam Cherubini

>What glue are you using? Titebond needs, depending on the species and surface prep, 250 psi to develop bond strength. Your rope approach and most of the other methods offered so far probably won't get you there. You may have trouble achieving this with pipe clamps. At the very least, that kind of pressure won't be achieved uniformly (with pipe clamps) across the joint (which is probably good enough).

FWIW I did some quick and very dirty calculations. With a normal pony pipe clamp, you need to hang about 16 pounds from the handle to develop 250psi or so (or its somwhere in that neighborhood).

So I think you ought to invest in 8 to 10 pipe clamps to avoid risking your workbench. Crazy to come up with some wacky scheme.

So here's my wacky scheme!

I'd be inclined to get gravity on your side somehow. Stack the boards on edge, then use a car jack (or preferably several to push the assembly against the main beam of your house. A set up like this could break common joists. I'd start by practicing with a bathroom scale in the mix somewhere. 250 pounds over the width of a 2x4 is not 250psi, but at least it would give you some idea of what you are getting.

Lastly, I'd like to say, I asked franklin for low pressure bond data. They didn't give it to me, but verbally said it had little or no properties (strength). Most of us who have experience with titebond would say "hooey". It does have low pressure properties which may or may not be good enough for you.

I think you should just go get the pipe clamps. And to the rest of you, I think you should start with a set of 8-10, 4' pipe clamps so you can make dining tables, workbenches and the like. You can always use them for smaller projects or cut them down or get smaller pipes for smaller work.

Adam

P.S. Kudos to thems what knows the longer text of my subject line! To those what don't, google. And don't forget to throw a penny on Ben's stone on your next visit to Quaker City.

Rent

Todd Stock

>Rent some clamps. My local rental place has both pipe and I-beam clamps. There are work-arounds, but why bother?