Hello,
I am new to woodworking and trying to build a small (2’x4′) split top Roubo workbench. I currently have 4 pieces of 2×12 (Douglas Fir) that I would like to laminate to get 2 pieces of 4×12. They would end up making the top of the workbench. My question: is there a structural difference between gluing two 2×12 flat on top of each other, or cutting them down into 2×4 and gluing them sideways? It seems that most people do the latter on the internet, so I am curious to know if there is a reason.
Thank you for your time and advice!
Replies
I'm guessing these will be two assemblies, with the split going in between? One of the problems is, face gluing these two 12 inch wide assemblies, it is more susceptible to twist. You could easily have one half twist in one direction, and the other half twist the opposite way. You can have a really hard time keeping the whole thing flat.
The issues with gluing face to face is it's one really large surface area to spread glue and then clamp. You can use screws from below, but I would take all the screws out when it's dry. Sooner or later you'll try to drill a dog or holdfast hole right into a screw.
Without screws, you'll need more clamps than if you laminate in the usual way. And deep clamps to reach the middle of a 2x12.
You are also more likely to have gaps between the slabs than you will from ripping and laminating on edge.
You can do it, but it's not the direction I would go. And I wouldn't do a split top, either. If you use it to store tools, they just get in the way. And it's guaranteed to swallow hardware and tools. I would for sure just make a solid one piece top.
My small upstairs bench is made from Douglas for, and I like it as a benchtop wood.
Most 2x12s are flat sawn which cup as they dry. Your bench top will suffer accordingly. Cutting them into 2x4s and laminating them that way puts the quartersawn edge up. Combine that with arranging the boards so that the rings alternate will give you a much more stable top. The top will still move a bit over the years, but not near as much as stacking two 2x12s on top of each other.
Almost forgot. Do any of your boards contain any pith -- the very center of the tree? If they do, it will split. Pith always splits. If that's the case, you should remove the pith for sure.
I would not rule out a split top, there are advantages and it's certainly easier to mill half a glued up top. You can add a removable insert between the two tops and still be able to use the gap for clamping by roving the insert
Check out the Bench Crafted plans.
Face gluing is a bad idea, the top will not stay flat, which is the main goal. To wind up with a 4" thick top, rip the boards into about 4.25" wide strips, let them sit for a week, and then joint and plane before glueup. You'll need more wood than you think.
If this is construction grade lumber use the outside edges for your top and the inside strips for your base... if it is usable after it settles.
Stack the lumber in stickers for several weeks construction lumber typically runs over 20% moisture content.
Rip boards off either edge of the 2x12. This will give you either rift or quarter sawn boards, and avoid the center pith area. Cut to rough length first.
Rip more than you need, just in case you get a wild one that comes off the saw like the onramp to the interstate ;-)
Rip them 1/2" wider than final dimension, then sticker for several more days. This allows further acclimation and destressing.
Do the same thing with milling - 2 or 3 sessions, 2-3 days apart, no more than 1/8" off each side at a time.
Although this is a small bench, the same principles apply. If you start with well acclimated, relaxed wood, you will have a much more stable top, that when flattened is more likely to stay flat!
I would rip-n-flip and laminate the smaller strips for greater stability.
Thank you so much to all of you for your insights!! So many things that did not even cross my mind... This makes a lot of sense now. I will do my best to follow your numerous advises.
This forum post is now archived. Commenting has been disabled