Leather Bar Stool Seat Cover With Diamond Stitching Pattern

Since I don't know how to upholster, sew or anything remotely related, this is a practice project before I cover a motorcycle seat.

I've got a cheap bar stool at a bench in my workshop, but its terrible. The cushion has only millimeters of foam, and after a few minutes you have a numb bum.

I figured I'd craft a new stool, and practice using my homebuilt tube bender (to make the frame) and craft a custom cushion cover out of leather with the diamond quilting pattern I want to use on the bike seat. 

Just to complicate things, I'll use my grandmother's original 1953's vintage treadle-operated Singer 201K sewing machine, which I've never used to sew a single seam.  

In this Instructable, I'll show you the design elements, the build process and materials and the finished seat top.

The existing bar stool I mentioned about is about 720mm from the ground to the top of the cushion, and this height seems OK for my workbench. So no need to overthink it, I'll just copy it.

Three legs - rather than four - means it will always contact the ground, now matter how bad the floor level or surface condition.

Since the old stools had almost zero cushioning, I bought a chunk of 100mm thick high density foam for the cushion. The piece is large enough to make this seat cushion and the seat for my motorcycle project. 

The seat diameter landed on 330mm; pretty close to my existing bar stood, and this diameter was accomodated by the piece of foam I purchased, plus the 16mm plywood I had on hand to make the base.

From my local leather supplier, I bought some nominal 1.5mm thick black leather. 

I modelled the whole seat in Fusion360, for a couple of reasons:

1. More Fusion 360 practice
2. Easy to work out (and adjust) the leg length to achieve the desired height.

My plywood stock isn't fancy - its construction grade - so I located a space with minimal knots showing on the face. At least one side looks nice, but its somewhat pointless as neither side of the plywood will be visible at the end of the project.

Whenever I make something circular from wood or metal, I'm inclined to drill a tiny hole in the center. This allow you to come back and mark out a concentric circle or some other feature. I've learnt the hard way a number of times so now its a habit. I punched a tiny 1.5mm hole in the plywood.

Using a compass with a sharp lead, its simply a matter of sketching out the circle. Since you have a hole right through the plywood, draw the same circle on the other side. Don't forget that the compass has to be set at half the diameter, so in this case, 165mm.

There are a bunch of ways and smart people who can cut out very precise circles with table saws, routers and home made jigs. 

Since the plywood will be covered, I dragged out my small wood bandsaw to trim the plywood disc very close to the pencil line. 

A jigsaw (sabre saw) would be acceptable, however, my jigsaw suffers from a deflected blade when cutting curves, which results in a bevelled edge requiring a lot of sanding or finishing to make square. This is much less of a problem with a bandsaw which has blade support above and below the workpiece. 

With the plywood disc very close to finished size, I used a bench-mounted belt sander to carefully sand right to the compass line. Having the circle marked on both sides of the disc helps ensure the sanded edge is square to the faces.

While the plywood is acceptable as supplied, its much nicer after further sanding. I hit the faces with 80, 120 and 240 grit sandpaper in a random orbital sander. When the 240 grit was installed, I also sanded a tiny bevel around the perimeter of the disc on both sides to minimise chipping and injuries on the sharp corner.

The finished plywood disc is perfect for marking out the cut line on the foam. Knowing I'd want the cut line on the top and bottom of the foam (to square up the cut edge), I needed to mark the center of the foam cushion on both sides.

Using a bamboo cooking skewer, I was able to pierce a hole right through the foam cushion, center the disc on the skewer on both top and bottom of the foam, and trace around the disc perimeter.

I probably should have done more research on this, but I'd read that bread knives or reciprocating electric carving knives are useful for cutting foam.

Regardless which I used, I expected to be doing a lot of sanding to ensure my cushion was finished as a tidy cylinder.  

I grabbed the bread knife from the kitchen and hacked away. It worked, but not well. Big long straight cuts, like hacking the piece of foam into two, worked fine. Trimming small wedges from near the perimeter marks, not so well. 

Luckily I have a bench-mounted belt sander. It took a good 30 minutes to carefully smooth the ragged edges of the cushion. I'm not sure how you'd do this job without some sort of belt sander.

Those with a keen eye will notice the cushion diameter is bigger than the plywood disc, by the amount of the thickness of the line I traced around the disc on the foam. Ideally, they'd be identical, but I was facing a lot more sanding.

If you know a faster / better / whatever way of cutting an accurate cylinder out of high-density foam, let me know in the comments.

The plywood disc is also perfect for marking out the leather disc needed for the top of the cushion.

I guessed I'd need a 12mm seam allowance around the perimeter, so I used dividers set to this measurement, and traced around the plywood disc sitting on a piece of leather. This allowance turned out to be acceptable.

While this divider technique has worked for me on veg-tanned leather, the resulting scribed line wasn't as visible on this heavily grained and soft leather. I'm sure there is a better way. If you have some ideas, put them in the comments too.

Thinking ahead, I assumed I'd need a relatively accurate edge on the circular cushion seam to match with the leather skirt. This was the reason for the 12mm scribe with the dividers.

But being so difficult to see made cutting the disc with an accurate 12mm seam allowance difficult. In areas with a clear scribe mark, I could use scissors to cut to the line. But in other areas, I fumbled around with scissors, a craft knife, and even a plastic french curve used as a partial cutting template.

In hindsight, it might have been worthwhile making another wooden disc the diameter of the seam (in my case, 330mm plus 12mm all the way around, so 354mm). Something thinner, like 3 ply or 5 ply or hardboard, that would act as a cutting template for a craft knife or box cutter travelling around the perimeter.

Once the leather top disc was cut out, I used a dressmaker's pencil to mark parallel lines at 20mm spacing across the top. This is my guidelines for sewing the diamond pattern. The cutting mat I have made this easy by simply aligning my ruler with the printed lines on the mat.

Then I turned the leather disc about 45 degrees (until it looked good, no other critera), and repeated the 20mm parallel line pattern to finish forming up the diamonds on the surface.

Now the plywood has finished its duties as a cutting or marking template, I gave it a coat of primer then a coat of flat black paint. 

I'm in a couple of leatherworking Facebook groups, and I often see/hear comments that leather cannot be sewed with a domestic sewing machine. I've proved I can sew 1.5mm leather with a Singer treadle machine, so maybe some clarification of those comments is required:

1. Obviously thickness of the leather is important. You can't sew 4mm thick leather belts with a domestic machine. 
2. Leather-specific needles are apparently made with a special point to pierce leather. I bought a couple of different packets to try. They're only a few dollars each. 
3. A strong polyester thread might help. I discovered after I bought the thread for this project that an even heavier-duty thread is available. I'll buy some for my motorcycle seat. 
4. I'm not sure a Singer treadle machine is considered a domestic sewing machine?

This machine was bought new for my grandmother. Its a Singer 201K model, and the serial number makes it 1953-manufacture. Its in immaculate condition, with lots of original accessories. My mother learned to sew on it when she was a child, so I've gotten a few tips from her (plus a few more from YouTube).

This machine is fairly rudimentary. It can only stitch straight (not zig-zag or anything fancy) and the only adustment is for stitch length (measured in stitches per inch) and needle thread tension. Bobbin tension is apparently adjustable but I didn't mess with it. 

A treadle machine is about as eco-friendly as it gets. Its human-powered. Ironically the original manual with my machine advertises the electric motor conversion kit on the first page. 

The treadle operates a large pulley (somewhat a flywheel) under the machine. A circular leather belt transfers rotation from the flywheel to the balance wheel on the sewing machine.

The up-and-down motion of the treadle under your foot is connected to a link. This link is pinned to a crank which forms the axle of the lower pulley/flyweel. 

Its possible to inadvertently run the treadle backwards, but once you have a rhythym and some practice, it become easier. 

This is my approach. Your mileage may vary. 

The balance wheel at the right end of the machine (connected to the belt) should be spinning counterclockwise when the machine is running properly. If you grab the top of the balance wheel and spin it downwards, the machine will turn over a few times. Since it is connected to the flywheel and treadle (via the belt), the treadle will also move.

If you foot is resting very lightly on the treadle, you'll find a spot where you can start treadling and keep the machine running after that initial spin of the balance wheel.

On my machine, I can loosen the drive betwen the balance wheel and the machine mechanism itself, and operate the treadle without driving the machine mechanism. This is great for practice. Additionally, the bobbin winding mechanism is driven by the treadle, so winding thread onto a bobbin also provides treadle practice. 

I grabbed some scraps of leather to test. The needle was changed out for one of my new leather-specific needles.

I set the stitch length to 8 stitches per inch. No good reason, just seemed like a good starting point. 

I set the thread tension to zero and ran about 100mm of stitching on a single layer of leather. Then I increased the tension to "2" on the dial, and ran another 100mm of stitch. Repeat for tensions "4", "6" and "8". On inspection, the "0" or minimum needle thread tension gave the best stitch appearance. 

Stacking two layers of leather together, I checked the same thread tension was acceptable, and its seemed ok. 

The wadding is used to push the diamonds up between the stitching.

In the local sewing supply store, I found a range of different materials in the quilting department. I selected a 100% polyester material. Considering the "real" project (motorcycle seat) might get wet, I didn't want any natural materials inside the seat that may rot if they were wet. Yes, I know leather is a natural product too, but I can seal and treat the leather, and well, leather is cooler than vinyl. 

On good advice from my mother (a very capable seamstress), I backed the wadding with a piece of cotton cut from a bedsheet. This is to reduce the risk of stitching pulling through the wadding. 

So, the leather is on top, wadding in the centre, and cotton backing on the bottom.

This wadding was only available in one thickness. I sewed a test piece to set the machine, and it looked acceptable with one layer of wadding. However, when the finished cover was pulled tight over the foam cushion, the diamonds didn't pop as much as I'd like. After I was finished, I sewed another test piece with double wadding, and it looked a little better. When I sew the motorcycle seat, I'll double up the wadding.

Sewing the quilting was straightforward, as its simply a lot of parallel stitch lines through leather, wadding and backing. 

I started in the center with the longest stitch runs, just to get a rythym before I had to stitch short lengths.

I lined up the groove in the presser foot over one of the pencil lines, and aimed to drop the presser foot within 5mm of the edge of the leather. Then I'd turn the machine over by hand to lay two or three stitches, then reverse the machine to backstitch over those first stitches. This is supposed to minimise the starting stitches from untying. 

Then it was time to get treadling. I'd flip the machine into "forward" and turn it over by hand to pass the backstitches, then aim to start treadling as soon as possible. Following the pencil line was simpler than I thought. The machine kept the material very straight - it really required no "steering" to follow the line, just gentle guidance. 

At the end of the stitch line, I backstitched again, released the presser foot, cut the threads and start again.

It took about an hour for me to quilt the top of the seat cover, which was 20 rows of stitching in each direction, 40 rows in total and 80 backstitches. My treadle action had improved dramatically by the end of this step!

The perimeter of the circular cover was (pi times diameter, 3.142 x 330mm) just over a metre long. Rather than chopping a long strip out of middle of my hide, I cut two pieces from the edge. I figured I would need one seam, why not have two? Note, I rounded up from 103cm to 110 cm total skirt length to allow for the seams.

First step was to join the two shorter pieces to make the longer piece. First time round, I just put the two "good" faces together and zapped two stitch lines down the edge. But as I assumed there would be a lot of tension on this seam, I unpicked it to try something different. 

As you can see from the photos, I left one piece longer, double stitched it from the "wrong side", opened the seam, and double stitched it from the "good side". This gave me four rows of stitching. It also looked pretty neat with the constrasting red thread.

Now it was time to secure the skirt to the top. The reason I was careful to cut the top leather disc accurately was to give me a line to follow with the sewing machine presser foot. You can see in the photos I used stationary paper clips to clamp the skirt to the top. After a while I figured I could just hold it in place to achieve the same result without having to mess with clamps.

I turned the machine over by hand for this first run of stitching. I figured I wouldn't be able to steer the curved edge of the top leather disc and hold the skirt in a accurate position if the machine was moving rapidly via the treadle. 

At this point, I had the seam between the top and skirt all the way around the perimeter bar the last 50mm or so. This was to allow the second skirt seam to be finished in the correct location. 

Test fitting the cover over the foam cushion, I could pull it tight, mark the free ends of the skirt to the correct length, leave a seam allowance and trim the excess couple of centimeters off.

Of course, I'd snookered myself and couldn't replicate my four-stitch seam on this free end, so I just wiggled the ends under the presser foot and zapped down two rows of stitching, then went back and closed up the final 50mm of the skirt to top seam. Some slight inaccuracies in my measurements and sewing meant this seam wasn't as pretty when finished. I think if I finished the skirt to top seam BEFORE joining the ends of the skirt, I might have got a better result.

For the final step, I ran a parallel stitch line inside the skirt to top seam to double it up and increase its strength. I did this with the treadle, as I could follow the first row of stitching with the edge of presser foot pretty easily.

Having studied upholstery at the University of YouTube, I'd seen others complete similar projects by punching in the first staple, say at 12 o'clock, putting the second staple in at 6 o'clock, then 3 o'clock, then 9 o'clock. Then continually back and forth across the seat base, progressively splitting the gaps between staples.

I grabbed my trusty hand stapler and installed some 6mm staples. I figured this bad boy would punch leather and plywood easily. Alas! That assumption turned out to be wrong! Staples made it about half way. I thought I'd finish them off with a hammer, but this just bent the staples over. 

I was pulling the leather over the edge of the plywood base pretty hard, and after a few staples were installed I flipped it over and checked the cover. I found it was lop sided from excessive tension in some places. Pop the staple out, relieve some tension and re-staple. You might also note there wasn't a whole lot of leather available to yank on to pull the cover tight before stapling. I could have increased the skirt width to accomodate this. It worked, but only just. 

I have a lighter duty electric stapler so I thought I would try it. Sure enough, it punched staples in no problem at all, so it was pressed into upholstery duty and did a fine job.

On inspection of the finished cushion cover, I could see some of the stitching from the skirt to top seam visible. No doubt due to the tension on the cover being pulled over the foam and stapled to the base, perhaps using finer stitching on these seams would increase its strength and prevent it being pulled open when the cover is installed.

I have to say, as a first upholstery project, first time sewing leather and first time using a treadle machine, I'm very happy with the result. 

I also discovered a heavy duty version of the polyster thread I used, so I'll pick some up for my motorcycle project.

I'm confident tackling the motorcycle seat project, and here is a summary of the lessons I learnt:

1. Double up the wadding to make the diamonds pop more

2. Increase the stitch count-per-inch for the seams to increase strength

3. Allow more width on the skirt.

Hopefully this project gives you a starting point for trying some upholstery, leatherwork or treadle-powered sewing! Thanks for reading this far!