What weight of leather are you using? If it's fairly light, any machine should be okay as long as you use a leather needle and appropriate thread. The heavier the leather, the more difficult it will be.

Thanks everyone. I'm now convinced to go ahead and try using one of my older Singers for the job. The cushions are a simple, square shape, so it shouldn't be too difficult. I'm looking into purchasing a teflon foot, or possibly just using my walking foot to help the machine sew smoothly and evenly. The leather is insanely expensive, so I don't want to screw this up. :( That being said, a new couch is probably 3-4 times as much, so I guess that I'm, "saving money." ;)

~ C

I think that there's special thread just for leather. I'll definitely get some leather needles.

~ C

My neighbors have a very busy business just repairing leather clothing, and sewing patches on leather. They almost exclusively use Singer treadles. I did convince them to try a "newer" (than their treadle, LOL), vintage electric Singer because it had reverse on it...it worked but they went right back to their treadles!

when my kids were doing 4H horse shows, I made leather chaps on my old all metal Deluxe machine--use a leather needle. This was fairly heavy leather so I also used a bit longer stitch length. Worked fine, even putting in heavy duty zippers. I know have an old (50's) industrial Consew--it's a beast--goes forward/reverse but can sew anything.

My old stand by 401A goes through leather like butter.

I can sew through 3 layers of leather with any of my vintage sewing machines. Singer 301A, 401A, I have more but these are real workhorses. Just make sure you use a needle for leather.

As long as you are using apparel weight leather, a vintage machine with a leather needle is fine. My DH is a leather worker. I started him with a 1960’s white machine that I didn’t care about. It worked ok, but I eventually found an industrial pre WWI needle feed machine on Craigslist for $300. It does a nicer stitch, and longer stitch, but I would only recommend the industrial if you are going to do leather work regularly.

I have my Mom's Singer 201 and it's fantastic. Sews through almost anything. It's a real workhorse of a machine. A couple of hints for sewing leather. Like someone else suggested, be sure to get a leather needle. Second, use a longer stitch. If it's too short, it becomes like a perforation and the leather pulls apart.

If your layers are very thick, you may run into the issue of presser foot lift. Some newer machines may sew through the leather with the correct needle, but the presser foot won't lift high enough to get thick layers under it. I have run into this issue when hemming jeans also.

Also, stitch a bit slowly so your needle has time to clear the leather between stitches.

edit: My sis swears that putting a bit of regular scotch tape on the bottom of her presser foot makes it slick like the teflon feet. She says it works great on her vinyl projects.