Through the workbench design process I experimented with several different scissors jacks. I bought a scissors lift that was intended to be a transmission jack. This looked perfect, it was very wide and it had plenty of lift. There were two problems with this jack. First of all it did not have enough mechanical advantage and almost as bad was that it was of such poor quality that it just would not work. Next I tried an RV stabilizer jack. This was a huge scissors jack with an amazing 24” lift. I learned that these oversize scissors jacks actually have less mechanical advantage than the ones for automotive use.
I then bought a scissors jack at a salvage yard from a mid-90’s Chevy Blazer. This has 16” of lift and it works great! I recommend getting a scissors jack from a pick-up truck or full size SUV for the primary jack.
The lower scissors jack is used to raise the bench up onto the mobile base. For this I recommend getting one from a Honda Civic or some other small car. The reason for this is that some of the smaller jacks actually have a greater mechanical advantage than the truck jacks. This is important for the lower jack because it has to lift the entire bench up off of the floor.
So as it turned out, automotive jacks worked best for this application. A secondary added benifit to using automotive jacks is that they are very inexpensive and readily available at any salvage yard.
One important thing you want to watch for with both of these is how the jack handle attaches to the jack. Some jack handles have a hook on the end and the jack has a corresponding hole for the hook to go in to. Some others are driven by a nut, or something else. The one I had the best luck with is the style that requires a hook on the end of the jack handle. It will probably be a lot easier if you find this style of scissors jack. Fortunately, this is the most common style for automotive use.
I also learned a few special characteristics about this type of jack.
First, and most important is that the higher a scissors jack goes the greater the mechanical advantage. So, when it is near the top it has an unbelievable amount of leverage! Unfortunately, when it is collapsed is has a very poor mechanical advantage.
Another thing I learned is that scissors jacks move! What I mean by this is that as a scissors jack raises up the screw moves up with it. The screw also moves horizontally. It is probably easier to explain visually.
In this first photo you see a scissors jack from a Honda Civic. The jack is fully collapsed with zero turns on the screw. The top of the jack is 2-1/2" from the floor and the screw is even closer to the floor. Also, the screw is centered inside the jack.
In the second photo you see the same jack only now the screw has 4 turns on it and the top of the jack is 4-3/4" from the floor. Note that the screw itself has also moved up off of the floor.
In the last photo you see the same jack again. This time the jack is fully extended with 89 turns on it, and the top of the jack is 12-1/2" from the floor. Note that the screw is now 6" off of the floor. Note too, that the drive end of screw actually moved toward the centerline of the jack and the other end of the screw moved several inches to the left.
It is important to know this because you need to fit two of these inside of your bench. The jack you select might look just fine when you install it, but cause problems when you actually try to use it.
Fortunately, as I said at the top of this page; it is easy to find a scissors jack that will work for this application!
About Scissors Jacks