I've updated the photos to clean things up.
I've been overhauling my garage for storage and functionality.
My workbench is 16'x2', and although the length is great I don't always have a lot of room for large projects. I wanted to have an extension that could serve as a "return" but also be removable so as not to interfere with putting vehicles in the garage.
The result is a simple 4x2' framed table that uses carriage bolts to affix it to my existing work bench.
Step 1: Supplies:
(1) stock piece of 3/4" plywood from a big box store. I purchased the pre-cut 4x2' for ease.
(3) 2x4x8 studs, non-treated. It's indoors, and the kiln-dried were less than $2 ea.
A box of 1 3/4" wood screws
8 to 10 2 1/2 to 3" deck screws.
1/2" wood boring drill bit
Saw for cutting 2x4s: circular or miter
(3) 1/2" x 6 carriage bolts
(2) 1/2"x 4.5" carriage bolts
(5) 1/2" wing nuts
(5) 1/2" fender washers
Step 2: Cut Your Wood
The plywood is already cut. Decide if you want your 2x4s to be "on the end" or "inside the end" of the frame. I found it easier to cut the two long sides right to the length of the plywood, cutting one of the 2x4x8's right in half and screwing them to the plywood using the shorter screws.
Cut another 2x4 to give the two end pieces.
Set one of these 2x4s to the side. You'll need it for the next step.
The other small 2x4 can be fit to the end of the plywood frame and secured with the shorter screws.
Use the longer screws to secure the 2x4s to each other at the ends of the frame.
Step 3: Make a Template / Drill the Carriage Bolt Holes
If you drill through that remaining small 2x4 you cut, and the work bench, at the same time you can ensure an accurate match of your carriage bolt holes.
I used a scrap of 3/4" plywood I found and just nailed it to the top of the 2x4 to simulate how high I needed to set the 2x4 before using the drill.
Once I had the plywood scrap even with the top of my workbench I used some deck screws (the longer ones) and secured the 2x4 to my workbench.
I measured and spaced the three holes across my 2x4. It was about 21" in length (as I set mine inside the 4ft sections of the frame).
Once I drilled the holes, I removed that 2x4 piece from my bench and added it back to the plywood frame I just assembled.
You now have 3 holes in your frame and 3 holes in your bench.
Step 4: Insert Your Carriage Bolts to the Bench
Feed the bolts through from the front of your bench, putting the fender washers and wing nuts on the backside. They will not take much torque to secure when you use the table.
By leaving a few inches of slack with the wing nut you can pull the bolts out when you want to hook up the table, and when you're finished simply push the bolts back against the work bench. A wood chisel, tap with a hammer, or perhaps a 9/16" bit can widen the hole enough to allow the square of the carriage bolt to recede into the wood.
Step 5: Jigsaw Your Frame's Carriage Bolt Holes
After you've drilled the holes to the piece that sits in your frame, use the jigsaw to cut from the holes straight out to the edge of the 2x4.
I started with straight cuts from the hole to the edge of the 2x4, I decided to cut mine at a 45 angle about an inch up from the lower edge of the 2x4. This helps the frame settle onto the carriage bolts much easier.
The bench is a tad heavy. Any help lining it up was welcome.
Step 6: Add Legs
Measure the height needed from the underside of the new table extension to the floor and cut (2) 2x4s to length.
I drilled through the 2x4 frame into the leg and secured it with the 4.5" carriage bolt and wingnut/fender washer. Do this for each leg.
I jigged around the top of the leg to give it a shoulder and allow it to pivot into the body for storage.
After the legs were built I removed them and cut each leg's bottom by the thickness (about 1 7/16 on the board I had) of a 2x4 that I would use to secure the legs to each other.
This makes it easier to extend both legs together, and it ensures the legs do not become dislodged should someone/something come into contact with them. It also prevents me from applying unwanted torque to the legs in the form of a side load.
Step 7: Secure the Legs' Foot and Stow
I made the legs first, to the proper height--before making the foot--because my garage has a noticeable slope for drainage, and I wanted to make sure the legs were keeping the table level first. After that, simply cutting the legs down by the thickness of my 2x4 ensured they retained their proportions as they "came down" a bit.
I've got the wingnuts snug enough that I don't need a latch or snap, though if I intend to hang this for stowing (right now it just slides along side my bench) I'll consider it.
Thanks for viewing.