So I was looking for more information on the Pfaff 6 and this page came up. And I see not only the Pfaff 6 being impugned, but the Sailrite as well.
I know this thread is old but being a sailer and having done some sail repairs and canvas work, I certainly have an opinion. ;)
Sailrite
There have actually been several different sailrite sewing machines and basically all of them have been modified versions of somebody else's sewing machine. Sailrite also sells a "professional" model which is more like an industrial machine and can do things like 4 point zig-zags. And while it's true that multi-point zig zag machines have found a home in professional sail lofts, I think that's a fairly recent development, and perhaps limited to very high end/large sails. I don't own a single sail that uses anything other than a simple zig zag, - even my newer ones.
So the idea that you can't make a decent sail without multi-point zig zag simply isn't true. Sailrite's basic zig-zag machine fills a niche and it's hardly just for people wanting a portable sewing machine to keep on their boat for emergencies. If you're interested in the history of the LSZ-1 development, there's a good article here:
https://www.sailrite.com/ultrafeed-history
Obviously all machines are compromises and you give up things when you want the portability that an LSZ-1 provides. And one of the big things you give up is harp or throat size. Even sails for relatively small boats get pretty big and making sails with something like an LSZ-1 will be an exercise in patience and persistence. Making sails for a 60 footer is not going to be practical but the portable Sailrite might still be good for repairs and canvas work on a boat like that.
Pfaff 6
So I've learned some more about the machine from this thread and other places. I do agree that it's basically the same as a Pfaff 60 and I also believe it's a descendent of the Pfaff 30. And while it's clearly not an industrial machine, Pfaff borrowed a lot from its industrial division when designing and manufacturing the internals of the Pfaff 30, - as it did with several other models. It's wasn't unusual to find an old domestic Pfaff mounted on an industrial table with a clutch motor and knee controls.
That said, it is all too common that the word "industrial" gets applied to what is clearly a domestic machine. But some domestics are more heavy duty than others and do actually share things in common with industrial machines, - much like an SUV might have both car and truck like qualities.
I really can't say how well suited a Pfaff 6 would be for the kind of leather working the original poster had in mind. It might be terrible for that, - at least in its stock form. But it is not a typical domestic machine.
And FWIW, old Pfaffs were (and I think still are) popular machines for liveaboards to keep on their boats. Particularly the Pfaff 130.
