I used two trailer jacks to make an adjustable height work bench. I needed a way to store my new X-Carve CNC machine when not in use. You could modify this design easily to make an adjustable height standing desk.
Step 1: Modify Trailer Jack
A small pin is all that holds the hand crank on the trailer jack. Tapping it out and replacing the hand crank with a 48" rod ensures both sides of the work bench rise in sync.
Step 2: Re-Assembly
Drilling a small hole for the pin in each side of the rod connects the two trailer jacks together.
Step 3: Remove Mounting Bracket
I used a grinder to remove the mounting bracket from the trailer jack so it would fit in side my risers.
Step 4: Wood Risers (Guide Blocks)
I built two plywood boxes that fit perfectly in one another. Then the trailer jack goes in the smaller of the two boxes. A mounting plate is welded to the top of the jack which can be screwed to the inner box.
Step 5: Gears and Chain
Since the jack is upside down, two spur gears and #35 roller chain was used to bring the crank up to a comfortable height.
Step 6: The Frame
I used plywood to build 4 legs and connect them together. For my top work surface, I layered plywood with masonite to give is a slick finish as an out feed table for the table saw.
Step 7: Finished!
With this project I gained a large work bench, an out feed table, and a way to raise and lower my new CNC machine! I'm very happy with the results.