I found an old Singer model 152 (walking foot straight stitch) from about 1940. A man was selling his marine canvas shop and had it setting in a corner. He had three newer machines that he used and this one had just been taking up space for a long time. It had the motor replace with a bigger one at some point. I got it and the table for $200.
When I got it home and got it all cleaned up, I started playing with it just to see how it worked. One of the things I did was to see just how much heavy vinyl fabric it would go through easily. It went through 8 layers like they weren't even there. I'll bet it would treat a finger the same way so I give it a VERY healty respect.
However, what I wanted to say in responding to your question is that I would suggest you find one that has a reverse. Mine doesn't. I have found myself wishing that I had a reverse a few times like for tacking the end of a stitch, etc. What I have to do is either 1). Lift the foot and drag the piece back a little, drop the foot, and go again. This leaves a long piece of the thread open where you moved the piece but it works. or 2), Turn the piece around. This is ok for smaller pieces, but when I was re-stitching my boat cover it was a little impractical.
Wayne