Testing Leather on a Home Sewing Machine

Last week, I mentioned that I bought a home sewing machine for our family. My kids expressed interest in sewing, specifically in making stuffed animals and clothes. I have several industrial sewing machines for leatherworking, but they require adjustments for sewing thinner fabrics and can be a little intimidating for children. These sewing beasts in my studio could easily blast through several layers of leather, but adjustments were needed for the lighter stuff. I tried using my flat bed on some lining fabric, and it bunched and gathered like crumpled pieces of tissue paper. The kind of machine I needed should be lighter, slower, and more portable.

I haven’t used a home sewing machine since I was in junior high school home economics class. Back then, I was more interested in baking (well, eating, really) cupcakes. I didn’t care much about the sewing machine other than keeping my fingers away from the needle. The next time I looked at sewing machines was decades later for leathercrafting.

The kind of sewing machine you need for leather is quite different from a home sewing machine. It usually needs to be stronger, have a walking foot, and use thicker thread. Except for my brief childhood experience, I approached my sewing machine experience in reverse. Most people start with a home machine and transition to industrial machines. I was doing the opposite.

I had been wanting to try projects in fabric and thought the utility stitches of a home machine would be useful. Zigzag stitches, making button holes, attaching buttons, and stretch stitches. I didn’t need the fancy stitch patterns (yet) or embroidery. Though I could see myself monogramming my work, my kids would love to make embroidered designs. A future expansion, perhaps. I thought this home sewing machine would only be good for fabric. Since it’s vintage (yes, the 90s were more than 25 years ago), it’s built pretty solidly with a metal frame. It’s not a tank like an older Necchi or Singer.

Testing a Domestic Sewing Machine On Leather

Although this machine was intended for home use, I wanted to try it out on leather, specifically thinner leather. I often sew through various thicknesses on a project, especially with small pieces, such as wallets. The card pockets might be 0.7mm, while the sides could be pushing 4mm. If I set my industrial sewing machine for the thicker pieces, I have to make non-trivial adjustments so that it will sew thinner pieces. Furthermore, when I sew something very thin, it’s very hard to dial in the tension evenly.

Since my industrial sewing machines are meant for thicker materials, I wanted to try this home machine on the thinner leather. This way, I could skip the finicky adjustments and possibly eliminate the tension issues.

To test out my idea, I made three samples. They were all two-layer glued pieces, 3mm, 1.5mm, and 1.3mm thick.

3mm Thick Baseline With an Industrial Sewing Machine

3mm is a common thickness I use in a wide range of projects, from wallets to bags. For example, the liner and the outer layers on the zippered wallet are within 0.5mm of this thickness.  I had no illusions about this home machine getting through this thickness, and I didn’t try it lest I break a needle or worse. The glue makes it especially hard to sew through on a domestic machine. I created this sample as a reference for what I wanted the other stitches to resemble.

To create this baseline, I used my Juki 1541-S with a size 20 MBT, 3mm stitch length, and a size 18/110nm needle. The top stitch is brown for the top thread and white for the bottom thread, allowing me to see the tension more clearly.

1.5mm Thick Leather, Functional Stitch, Looks Secondary

I next glued and sewed the 1.5mm layers. This is a common thickness for sewing interior components together. For example, sewing card pockets to the liner is around this thickness.

You can see that when I sew through 1.5mm, it still gives a decent look, but the back could be improved. The holes are bigger, and the top thread is just starting to peek through to the back. Note that I didn’t modify the industrial machine from its optimized 3mm thickness setting. There are several adjustment options I could make, such as switching needles, adjusting thread thickness, and adjusting tension. These require a bit of finesse and trial and error due to the various combinations of leather, thread, and needle size. We’ll see later if switching to a domestic machine is better and faster than doing the changes on the Juki.

1.3mm Thickness, Decorative Top Stitch

The last sample is 1.3mm. This is my target for the domestic machine. It’s a thickness I use when sewing a fold-over on a single-layer card pocket for wallets. If I can sew through 1.3mm, I will easily be able to sew through anything thinner. This seam doesn’t need to be particularly strong. It’s just holding the foldover down, which is already secured by the glue and the seams on either side. You do occasionally see the other side, though, so balancing the tension is important to ensure the back looks good.

Home Machine Tests

I first tried 1.3mm on the home machine. This was my target thickness, and it was something I would use where I needed both a good look and a functional stitch. As mentioned above, this is primarily a decorative stitch. Dialing in the tension was important, especially when using two different thread colors for the top and bottom.

For my first test, I used the same #20 MBT thread, 3mm stitch spacing, and a size 18 / 110nm needle. This is the thickest needle I could use in my Necchi home machine, and it was a specialized needle specifically for leather. I measured the needle thickness and confirmed it was virtually the same as that of the Juki.

I was surprised that the holes were bigger on the home machine needle, even though they are the same size. The tension is also off as you can see the brown thread poking through the bottom. This would be ok if the two threads were the same color, but not if they’re contrasting. I tried some variations, such as adjusting the top and bobbin tensions, with similar results. At first, I thought the Necchi could not pull the thread through fully. It is very underpowered compared to the Juki. Both machines do this, though, so it must be something else.

I also wanted smaller holes for a finer look, so I switched to a thinner size 12 needle. You can see it’s a much finer hole. I’d have to switch to my Doldokki 2.12mm/12 spi pricking irons to get in that small a range. Even then, I think these machined holes are still smaller.

I knew this would not help me with my tension issue, as the smaller holes meant it would be even harder for the thread to pass through. They might hide the imbalance a little better since they’re smaller. No luck though.

I realized this would be a hard thing to dial in. Size 20 MBT is 0.3mm thick, so crossing two threads in a stitch could be 0.6 mm in total. With a 1.3 mm-thick piece, this leaves just 0.7mm of wiggle room to get the tension right. By comparison, my earlier 3 mm-thick baseline piece has a much easier 2.4mm range to play with. Still, I wanted to see if I could dial in this stitch further. After all, it is fine leatherworking we’re going for.

My remaining variable was thread thickness. I switched to a thinner domestic thread, 0.15mm thick (TEX 40). In the first two results, the top tension was too high compared to the previous setup. By the third version, the stitches were looking great. The thinner 0.15mm made all the difference. The tension was easier to adjust, and the stitches were much finer. I could reduce the stitch spacing to 2-2.5mm for an even finer look.

1.5mm Thick, Pushing the Limits

I next tried 1.5mm. The primary objective for this thickness was to see if I could get through it. This would be for functional seams, such as attaching card pockets to the interior liner. It should be strong, and the tension could be slightly off as long as it’s functional. Since I already had a thinner needle and thread in the machine, I tried this combination on the 1.5mm thick piece.

Not a bad result. I ran out of bobbin thread on the first line, which is why the bobbin thread shows. With more thread in the bobbin, the following line reverted to the earlier version. The top thread is visible on the bottom, but this can be easily adjusted. Good to know this would work too. I didn’t spend more time on this because it’s not a combination I would use. For these thicker pieces, the seam would be more functional, and I wanted to switch back to MBT size 20, doubling the thread thickness and increasing the seam strength. I also noticed the number 12 needle was struggling to get through the leather. I didn’t want to risk breaking a needle, even though it was probably ok for short distances.

I reloaded the size 18 needle and the size 20 thread, and then changed the tensions back to their previous settings. I had to do two rounds of adjusting the top tension. They were very small, however, and easy to do. The result was decent if not a little shaky. I could feel the machine struggle through the leather, and it showed on the back. It was much less consistent than the baseline stitch from the Juki. This was acceptable as my goal was to have a functional stitch where the back didn’t matter.

Conclusions

This was a lopsided comparison to begin with, and I knew it. I was pitting an old $70 Necchi against a Juki 1541-S, over 20 times the cost. The Juki can punch through material more easily, hold tension more consistently, and has a much wider range on the thick end of the material range.

My goal, however, wasn’t a domestic replacement for an industrial sewing machine. I wanted to see if I could use this home sewing machine for thinner leather, so I didn’t have to switch my settings. For these purposes, it worked well. I could easily sew 1.3 mm-thick leather and make fine adjustments to dial in the stitches to look perfect. I estimate I could sew anything under 1.4mm and have it look and function well.

Sewing 1.5 mm-thick leather on the Necchi was a mixed bag. It struggled through the seam. If I had used softer leather or hadn’t glued the pieces, the machine wouldn’t have worked as laboriously. For my particular use case, sewing pockets to the lining, I can stay on the Juki, adjust the bottom tension slightly, and never worry about it. If I wanted the back of the stitch to look good, I’d have to use softer leather or not glue it together and only clip it instead.

Overall, having an extra machine, tuned for thinner materials, is great. I can tune the Necchi for 1.3mm thick sewing and switch back and forth between machines easily. The Necchi allows for fine adjustments in the tension on the thinner end, which is all I need. Takeaway: If you’re a leatherworker looking to sew thinner leather or fabric with a home machine, a vintage Necchi or similar can do the job, up to ~1.4mm thick.

I can also use this machine for fabric, its intended purpose. That expands my range to garments and helps me to make fabric mockups for bags more quickly.

If I wanted to really dial it in, I’d probably have a beefier domestic to get through 1.5 to 2mm thicknesses. I could also acquire a lighter industrial machine and keep it tuned to work with fabric and thin leather. I actually use a version of this setup now, as I own a Pfaff 335, which can work with both medium and light leather. I tune the Juki for heavier work and keep the Pfaff at medium, or vice versa. Having a third option now makes it easier to switch between thicknesses. I can also see how people end up owning many sewing machines, especially if they’re trying to crank out pieces.

Comparing the Necchi to the Juki was night and day. The Juki was so much stronger in punching through the leather and pulling it along with its walking foot. That said, I can see how a slightly stronger domestic machine, such as an old Singer or a modern heavy-duty home machine, could work with light and medium-weight leathers. They’re less expensive and take up less space than an industrial. I also love this little Necchi machine. It’s easy to use and doesn’t blast through delicate fabric like my leather sewing machines; a great addition to our studio.