Scissor Bench - Adjustable Height, Motorized Workstation

I salvaged an old drive motor from a lift chair I replaced for my father. The chair was junk but the motor and drive was still working fine. So I removed the chair elements and kept the motor and actuator.

I wanted to make a scissor style lift workstation. One that would work more at a seated position. Ideally I was making a scroll saw bench that could easily change height for another person to comfortably use. But I realized quickly that you could use this in a lot of different applications. An out feed for my table-saw, joiner or planer.

I made this with all construction grade material to keep the cost to around 20 bucks. I used old window washing or paint extensions sticks for the pivot points.

I started with a sketch on paper gathering measurements from my scroll saw as I went.

I needed to figure out the footprint for my scroll saw. Next I measured how much travel distance the actuator has to it. And lastly I got rough idea of what was comfortable for me while seated in a standard chair. I then switched to Google sketch up to build a more accurate model of what I was making.

You can download the Sketch up model by clicking here.

https://3dwarehouse.sketchup.com/model.html?id=u0943ebb0-dc9e-462e-93c7-66161971b023
 

A quick stop at a home store yielded a couple 2X10X8. I made the plans with 2X4s in mind but you get better quality material when you get the 2X10s and rip them into 2X4s yourself. I had some old window washing sticks on hand already. They are 1-1/8” thick and work perfectly.

I (rough) crosscut the material for easy handling in my cramped shop first. Next, I removed the blunt edges by ripping 1/8” of material off of one side only. I did all of the cuts at once for more accurate results. I then ripped the boards at 3-1/2” wide. Finally, I crosscut them to finished dimension.

The scissor legs consist of 4 lengths of 2X4s with three holes in each one equally spaced apart. This sounds easy enough, but I had problems. There was no room for error on this. If your holes don’t align perfectly, you’re going to have problems too. The boards MUST have equal widths and lengths. A drill press comes in handy here. I drilled the first scissor leg, all three holes then clamped it onto the next board and drilled the holes using the first as a “key” for each board after. When it’s done, see how well you did by inserting a dowel through all 4 boards into each hole. It really is the moment of truth. You don’t want to bang it with anything. Maybe a bump with the heel of your hand but that’s about it.  Remember you can sand the dowels if you need to and use paste wax to free it up. But you really don’t want it too tight or loose.

Sorry for the lack of photos in this step. I am a one-man-show and this was a tough step for me alone.

The frames are nothing more than 4 boards on edge, glued and screwed together forming a box. On the longer sides of the box I need a single hole at one end and a slot that the sliding dowel will slide on, on the other end. Use a router, jig saw or drill press. I glued up the sides with a slot opening already there, and drilled the hole for the stationary dowel.

NOTE: I built the frames twice. I loaned my jig-saw to a neighbor and he returned it broken. I ended up ruining the first set of frames when I tried to clean up the slot with a chisel because of the bad cut from the jig saw. Anyway, moving on.

I made ten washers with a hole-saw and 1/8” MDF hardboard. 2” hole saw to make the large washer and a 1-1/8” for the center hole. These washers went everywhere there is friction between two boards.
I also found some proper 2X4 scarps that I could make into a perfect square. Then I drilled a 1-1/8" hole through the block after marking centers. I then chucked these small blocks onto my lathe with a four jaw chuck and rounded the outsides. I didnt bother sanding, my cuts were nice enough :)
 

I glued and screwed some supports for each set of scissor legs. This is simply a 2X4 between each opposing matched leg clamped and screwed tight. Make sure you have the dowels and round spacer blocks in place and aligned before clamping and gluing the piece. You don’t want any errors.
This was nothing special. I just align all the scissor supports with the lower frame and have the dowels in place as well as washers.Then measure the length you need for each scissor cross support.

I had to remove the old brackets from the chair frame. I used a reciprocating saw and about 8 blades to cut these pieces out properly. I then used a grinder to grind off any and all sharp edges on the two pieces, drilled a hole in one that needed it. Then cleaned them.

Next I placed the actuator arm and motor in place and plugged it in to test the travel distance. I had to place the brackets somewhere on the lower frame that it wouldn’t bind anything up. After strategically mounting the two brackets I installed the actuator and plugged it all up for a test run

The movement was smooth and nothing bound up or seized anywhere. I still need to mount the power supply. But before I can do that, I need to find the extension cable. Its here some-where, I just gotta find it.

I found some scrap 3/4" plywood for the top and cut it to fit. Then, I removed all the dowels and sanded all the pieces with 220 grit. This was time consuming but it does make everything look better. With everything sanded smooth, I rubbed on a thick coat of paste wax. The past wax will help with any paint or glue that could drip on it as well as help with any moisture issues.

I'm a big guy and am able to sit on it. It does "pop, crackle and squeak" when raising and lowering with me on it. but it holds me fine. :)

Thanks for looking