Introduction: Make an Adjustable-Height Table With a Car Jack
This is an adjustable-height table that lifts up and down using an automobile scissor jack.
It works far better than I anticipated, and I love it!
It was made as a craft and hobby table, designed with a few goals in mind:
- adjustable height range between 30" and up to about 42"
- top easily removed
- sturdy and strong, but relatively lightweight
- use up a bunch of scraps from my shop
This table was made to be adjustable on a per-project basis, depending on which height is most comfortable to work at: for sitting and sewing, standing while building models, soldering, tinkering, etc.
Update: After initially posting this project, I've seen that others have done similar tables with excellent results. Check out https://www.youtube.com/watch?v=LKUVgv_iLtM for example, which has a fantastic locking mechanism built in. So clever!
Step 1: Overview
The main design challenge with this table was creating a functional single-point, center lift mechanism, with four peripheral telescopic legs that provide smooth lift guidance without sticking or binding up. I'm pleased with how it all came together.
The table top is lifted by either hand cranking the jack or using a power drill with a homemade crank rod.
The jack I used has a effective lift range of 11.5 inches.
The table has three easily-set heights: 30", 35.75", and 41.5".
The jack is used to raise or lower the top surface to just above the desired height. Support blocks are then placed in each leg and the top is lowered onto the supports. Without these blocks in place the jack only supports the table top at the direct center, so blocks are necessary to remove any wobble or teeter.
When the supports are not in use, they stow inside little nooks built into the table structure.
Other heights could be achieved with different support blocks, and the table could be raised even higher by adding blocks on top of the jack itself. But for me, these three main heights are perfect for my needs.
Details are covered in the following steps, and should be helpful if you're interested in making something similar.
Thanks for reading along!
Step 2: Materials and Tools
I had a bunch of left over oak plywood scraps from previous projects that I wanted to use up.
However in order to make these useful I had to first glue them all up into larger panels. This isn't required of course, and I'd recommend using new materials if that's an option!
I had an old laminate table top and four casters that I finally had a use for. The table top is 30" by 48".
I purchased one 60" by 60" sheet of 9-ply (9 mm or 3/8") baltic birch plywood (about $35), as well as a cheap scissor jack from Walmart ($15).
Regarding tools needed, this project relies heavily on two main things:
- a table saw with a cross-cut sled
- pneumatic brad nailer
Other tools used include: drills and drivers, orbital sander, clamps.
Step 3: Build Telescoping Legs
The basic structure of the legs were built first. All of these pieces were cut using my table saw.
The inner and outer portions of each leg are 23" long. This accounts for the height of my casters, so if you're making this be sure to adjust leg length according to your own specific needs.
The outer sleeve portions of each leg are each made of four pieces of 3/4" thick plywood that are 3 1/2" wide.
These are glued and brad-nailed together, with a finished outside width of 4 1/4".
The inner leg portions are made in the same manner, from four pieces that are just a hair under 2" wide, resulting in a finished outside width of just under 2 3/4".
The first challenge with this project was to build in just the right amount of wiggle room with the telescoping legs. I wanted them to slide inside each other easily, but not so much that there is excessive wobble or slop.
About a 1/32" total gap on top and side of the inside leg portions provided what I felt was the right amount of play.
Step 4: Torsion Box Table Base
The table's base structure is made of two torsion boxes, or beams, between which the car jack rests.
Torsion boxes are strong and lightweight and easy to make out of plywood. Plywood provides precision and stability over time, whereas solid wood would be prone to expanding and contracting with changes in environment humidity, etc.
The lower beam is attached securely to the outer leg sleeve portions, and the upper beam is attached loosely to the inner leg portions. They are actually attached with paracord and basically hang and "float" in position. This is covered in detail later, though.
The beams were made with 5 1/2" wide pieces of 3/4" plywood along with pieces of 4 3/4" wide pieces of 3/8" plywood, and glued and brad-nailed together.
Further measurements and dimensions will depend on your specific needs, but I'm going to include plenty of tips and details that should be helpful as we go along.
Step 5: Add Casters, Mock Up Lower Beam Height
At this point, the outer leg sleeves had a 5 1/2" portion cut off using the cross-cut sled on the table saw. These portions will later be firmly attached to the upper beam, with the inner leg portions attached loosely within.
The casters were attached to the outer legs now, and the lower beam was test-fit to decide on the necessary height to attach it to these outer legs.
This height location depends on the collapsed height of the car jack, as well as the desired lowest-height of the table itself, along with a few other factors such as the thickness of the table top.
Mocking all of this up and making a few sketches and taking key measurements is very important!
Step 6: Leg Bosses
To mount the legs to the lower beam, I added a plywood boss (< explanation) to each leg.
These were glued and screwed precisely to each leg with the help of a little scrap wood jig.
Step 7: Assemble Lower Beam/Leg Structure
With the help of the bosses added in the last step, the legs were easy to affix to the lower beam in perfect position.
Legs were glued, brad-nailed, and screwed in place as shown in the photos. This is a surprisingly light-weight but rigid structure. I was very happy with it!
Step 8: Upper Beam Structure, Part 1
This is where things get a little tricky.
The top beam structure needed to precisely fit into the lower structure, so the legs do not bind up at all as it is raised and lowered.
To do this, the upper structure could not be built separately - it needed to be built into the existing lower structure, using it as a guide, in order to ensure that they mated together precisely.
The first step was to lock the upper pieces of the outer leg portions to each other as precisely as possible.
Everything was put into place inverted on my worktable, and pieces of birch plywood were added as shown, first with glue, brad nails, and then screwed into counter sunk holes.
Step 9: Upper Beam Structure, Part 2
The table structure was turned right-side up, and the beam portion was created by fitting it into place, piece by piece.
Each piece was carefully measured, cut, and added using glue, clamps, brand nails, and screws. With the main pieces attached to create the upper beam portion, it was removed from the structure and additional pieces of birch plywood were added to complete it.
Step 10: Add Paracord to Inner Legs
The inner leg pieces had pieces of paracord added so they could be tied to the upper beam structure.
On the top side of the upper beam structure holes were drilled and counter-bored, directly above the tops of the inner legs. The inner legs were tied in place, loose enough to allow them to wiggle freely within the upper portions of the outer leg sleeves.
Step 11: Test It!
After all the planning and building, there's that moment of truth that's really exciting . . and terrifying.
For this project at least, it was a happy moment of truth and not a "back to the drawing board" realization!
Step 12: Finish It
I had a pile of paint samples in my cupboard, and decided to mix them all together and see what I ended up with.
I was pleasantly satisfied with this purple-ish color, and as a shade of my favorite color, figured it was perfect for my new table.
The table parts were disassembled and painted by hand.
After the paint was dry I lightly hand-sanded everything with 220 grit sandpaper, and gave the pieces a few coats of semi-gloss spray lacquer.
The inner leg pieces were buffed with superfine steel wool and waxed with furniture wax.
Step 13: Make Supports
Eight support brackets were made from scrap plywood.
These are 5 1/2" inches tall, made from 3 1/2" wide scraps and were glued and brad-nailed together and finished to match the rest of the table.
Step 14: Add Jack and Pressure Plate
The jack was screwed to center of the lower beam, and a scrap piece of aluminum was added to the middle underside of the upper beam to act as a pressure and wear plate.
Step 15: Add Bumpers and Cleats
I used pieces of an old 1/4" thick rubber mudflap to create bumpers to add to the upper beam structure as well as each support block. These bumpers make everything stick together and avoid any vibration or chatter when I'm using the table for things like sewing.
I also added little cleats to the underside of the table top to make locating it to the same precise location on the base easy if I ever have to take it off. The table top is attached the the base structure with four small screws.
Step 16: That's It!
I really love this table so far. I've used it for a couple small sewing projects at the lowest setting, as well as for some standing sewing machine tinkering at the middle height. It's exactly what I needed, and I was able to use up a bunch of scraps from my workshop to make it.
Thanks for reading along. Thoughts, tips, questions are always encouraged, and if you make something similar be sure to leave a photo in the comments!