Need help with building a workbench top with glued 4x4s

If you have a router then it is very easy to flatten the top once you've got it glued up, so I'd just skip the dowels and clamp them boards up in pairs, then glue up the pairs, and then the pairs of pairs and so on until you have a top as big as you want. Let it dry, put it in place, and flatten with the router. (I like handplanes, but all the glue-lines make router easier.)
I'd also forgo the tempered hardboard or 1/4" masonite or all the other fake tops that are used to protect the bench. Tops get dinged, scratched, gouged etc. When it gets too ugly for you to look at, screw the rails on the sides and route off just enough to make it flat. That's one of the advantages of starting with a thick slab.

blue sky said:

What do you mean by "flatten the top" with a router?

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They all beat me to the answer! I just used a regular 3/4" straight bit. My benchtop is about 7' x 2.5" and I screwed the rails to each side. The entire top took less than a half hour and a lot of that was making sure the rails were parallel to each other. I then found the lowest spot on my bench and set the router bit depth so it just barely touched that spot, moved the sled to one end, turned it on and started moving. If you're not removing half an inch at a time and you've got a decent router, you can do it one handed with no pressure and it just flies - just cover the entire bench from one end to the other and when you're done it's flat.

Does it join your base by sitting on four fat posts (like mine) or do you have some other type base? My top I just laid on the four posts, and secured with four l-brackets. It hasn't moved, but then iagain it's heavy enough I could have just laid it up there with no brackets. When I did it with 2x4 on edge the base was 4x4 posts, again I just used L-brackets to secure. No allowances made for movement.

If your boards are on edge, then the majority of your movement should theoretically be up/down, not side to side so I wouldn't worry about it.

blue sky said:

joesbucketorust

I attached two pics showing where the bench lies now...

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Nice top. Just a few brackets should hold it, it shouldn't be moving enough to worry about elongated holes. You might want to wait until you get the vises before installing the top - if you need to rout out some space underneath for the rods it will be easier to flip the top than to route upside down backwards while laying on your back.