If your machine is one of the really old cast iron machines (all metal parts) that you can barely lift, you may be able to sew leather that's not too thick. Nearly all machines can sew on thin leather if you sew slowly & use a leather needle, but for med or thick leather, you'll need an industrial machine. I see these on Craig's List all the time. The old ones sell for less than $300. Machine's these days are made super-light with mostly plastic parts that don't hold up well. I found my heavy duty 1937-1941 Singer at a second hand thrift store & it works like it's brand new, but I can barely lift it! Be sure to regularly oil your machine!
Be sure to use a special leather sewing machine needle. The leather needle has a sharp edge that actually cuts the leather. Use a new, sharp one with each project. These are available at sewing machine repair businesses. They're not sold at all fabric stores.To get leather to move ovewr the feed-dog you'll need a foot with rollers on the bottom (so it won't stick to the leather) or you can try a Teflon foot.These can be bought online or they may come with the machine.
* PS. It's not about "retrofitting", you can't replace plastic inside parts with metal ones. If you have the manual it will say if you can sew leather. If it's one of the new "computer" machines & is light weight (very easy to lift) then only sew on thin leather & ultra suede using a leather needle. You can always try writing to the Singer company.
* A Note: Before buying most feet, you'll need to know if your Singer has a short shank vertical, high shank vertical, slant, or vertical type "B" pressure foot system. If the foot just snaps on, you usually don't need to know this. If it screws on the shank, you'll need to know which foot you have. You can simply take your machine into a repair place & ask them if you can't figure it out. Many times the feet sold for the Husqvarna/Viking machine will snap on to other machines. These cost more, (about $25 each) but are easily purchase ion the larger Joann Fabric stores where the Husqvarna/Viking machine are sold.
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