workbench construction guidance needed


  #1  
Old 01-31-03, 04:34 PM
ccarruth
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workbench construction guidance needed

Need advice on construction of workbench. Plans are to use oak slats, roughly 2" by 3/4', glued face to face, so wide part of slat will run vertically as top of table. This would be supported inderneath by at least 1 layer of 3/4" plywood, or 2 layers if needed.

Q: How much plywood is really needed for rigidity and strength - 1 layer or 2
Q: Can I substitute pine plywood (yes pine) for the maple
Q: Would if be better to mix the plywoods - one pine, one maple
Q: Is glueing sufficient for all layers, or do I need to use non-tapered wood screws to secure the plywood sheets to the oak facing?

Any comments much appreciated.
 
  #2  
Old 01-31-03, 05:07 PM
C
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It really depends upon what you want to do with the workbench. If you need a rock solid surface to pound, clamp, and plane, then be sure to make a heavy enough frame to hold it in place. It needs sufficient support under the top to make it stay rigid and flat. The support will help determine how to make the top. I want something I can pound on and will not flex at all. I usually make mine out of face fastened 2x4 fir held together with lengths of threaded rod and fastened to a cabinet base. This design is quited heavy and rigid. It will absorb blows without flexing or bouncing. Bolting it together with threaded rod avoids alignment problems that would arise from face glueing so many boards. Next I hand plane the surface flat. I keep the surface with johnsons paste wax. Most any finish will be damaged in the long run and I can just add more wax whenever I want and go straight to work.

For a layered approach such as you propose, I would use another layer. I would skip the pine plywood because it is difficult to find truly flat pine plywood. Shop grade birch would be a better choice. It could be MDF for the other layer. I would glue the plywood to the MDF on a flat surface or frame to keep the combination from warping during glueing. You could drill some pilot holes through the MDF to hold the MDF to the plywood while the glue dries. Then you have a rather heavy flat surface. Next you could glue the oak slats down one at a time to the MDF side of the surface. This would give you a flat surface to glue the oak to. I would think about using clamps and a caul to make sure that the oak stays in proper contact with the substrate during drying time. Alternatively, you could screw from underneath into the oak as you lay it to hold it while the glue dries. Or you could toe nail it into place with a flooring hammer. Or you could install the first course of oak, make sure it it dry 30 - 60 minutes at 70 degrees, then fit each added piece into place by glueing the edge and face and setting it in place then moving it back and forth about 1/2 inch to seat it. It won't move then and the glue will set without any problem. When you finish, you will have a heavy, solid top.
 
  #3  
Old 02-02-03, 08:40 PM
ccarruth
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thanks for the response

I see your point, and yes, I will eliminate the pine plywood. 3/4" birch is avalable.

In terms of how, I do have one more idea, mainly to avoid building a frame support for drying.

What about using two 2x4s to contain the oak strips lengthwise, and clamping across the face, with wide cawls, to a make a tight glue up and inusre the pieces to not move upward as the glue dries. Next, use another set of 2x4s on the ends widthwise, and clamp lengthwise end to end. The point would be to have sufficient pressure in both directions, and end up with the table top finished in one swoop.

To make this work, I think I need to use Tightbond II as the glue, as it has a slower set time, and would allow me time to get all the oak facing set in place before I make final adjustiments to the clamps.

Yes, No, maybe?
 
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Old 02-03-03, 06:12 PM
C
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Let me hit on my favorite way of doing what you propose. You glue the two layers of plywood, MDF or whatever together. Here's the easy way to attach the oak strips, again. I like this because there is no clamping involved after the first row.

First row. Glue and align and clamp in place for up to 30 minutes. Make sure there is no squeeze out under the edge. Now, for all the remaining pieces. Glue the edge and bottom, set it into place with a bit of a slide 1/2 inch of so to spread the glue, leaving it in position. Continue with the rest of the pieces.

Since the first row is not going anywhere, it will guide the placement parallel to the first row. If your strips are long enough so that one reaches across the full width of the top, then placing some kind of fence along one edge might help. Each piece so placed will nest snugly in position and will not move after a few seconds, so you can go on to the next piece. You can glue up the entire strip top in the amount of time that it takes to spread glue on the pieces and position them. Be sure and wipe off any excess glue with a damp cloth. With this approach, open time for the glue ceases to be an issue since each joint is made and completed by itself.

As far as a frame is concerned, I meant to use whatever you intend to use as a place to mount the top, not something extra.

If you glue the strips together into a sheet, mounting it on the others and gluing will present the same difficulty otherwise. You will have to contend with making sure that there is sufficient contact between the other two and the sheet of strips. There may be some challenges with alignment of the strips to glue them together on their own.

I am not trying to be adamant. I have edge glued many boards before in order to make wider solid goods. Alignment can be a challenge, clamps, cauls, and boards slick with wet glue. This other approach will avoid all that since the alignment is to the surface to which they will be attached. The attachment to the surface will keep the strips from becoming vertically misaligned.
 
 

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