Adjustable height workbench / assembly table
In my early years of woodworking and cabinet building, I spent a lot of time assembling things on the floor. I'd never worked in a professional shop, and I didn't have the room for an assembly table. When I went to work in the ML Bigelow organ shop, our primary assembly table was a dead flat surface of 10' X 5'. What a difference! With a dead flat surface, assembling cabinets to square is so much easier. With the work off the floor, assembly requires a lot less expressive language.
For my new shop, and especially for piano action regulation I wanted a nice assembly table, but also I wanted it to be adjustable in height. The pictures below show my creation.
The adjustable height will allow me to do action regulation work comfortably in both sitting and standing positions. The table top is 3' X 5' and the surface is dead flat within 0.5 mm. The flat table was constructed in as a torsion box, pretty much as described by the "Wood Whisperer" in this article. It features an oak apron which sits 1/4" proud of the table top. This allows a 1/4" piece of masonite to lay inside the apron. When the work surface becomes marred, it can easily be replaced. That's a nice feature!
I created the adjustable height mechanism by adapting an adjustable height cart sold by Harbor Freight. I removed the wheels and handle from the cart and fitted it to the base. The table top is fastened with lag screws and plenty of construction adhesive. There is a small amount of side play in the mechanism, so the table wouldn't be suitable for much pounding and hammering, but that's not what I had in mind. At all heights it is very stable vertically. The table has plenty of mass (about 300 pounds), which enhances its stability.