To be able to sharpen a saw properly, you need a vise that will hold the saw plate firmly and does not quiver and quake with each stroke of your file. This is not an efficient way to sharpen a saw, and only creates frustration for the saw filer, as well as dull or poorly shaped teeth, not to mention prematurely worn files.
I’ve used some old, small, cast iron varieties, and have mostly been disappointed with their performance. The jaws are not long enough, they don’t grip tight enough, and they vibrate something fierce. I do have an old Disston vise with the ball and socket base, pretty handy, and just fine for the occasional tune up or shaping. Great for the wood-worker who wants to tune up their saws occasionally.
But if you make saws for a living, you need a serious saw vise, with big jaws, plenty of holding power, and it should be as solid as a rock, and have minimal vibration. All pretty simple things, but not easy to find in a manufactured unit. I looked for an old acme, but to no avail.
The best answer to the problem? Make your own. This could be accomplished in all sorts of ways. I have all kinds of ideas flowing through my head, beautiful pieces of utilitarian art, monuments to the art of toolmaking.
So, this is what I came up with:

My Frankenstein saw vise
A hideous hodge-podge of salvaged/second-hand materials.
The main works is formed from a small cast iron Colombian bench vise I purchased for $15.00 at a second-hand store. The front jaw consists of a piece of oak with a strip of angled brass at the top, a piece of salvaged door threshold. This is what engages the saw, pressing it against the back jaw, which is a piece of aluminum angle from an old computer main frame, with an oak spacer, to allow for handle clearance. This has leather glued and tacked onto it, to further dampen vibration. The oak and brass front jaw is attached to the cast iron vise with a couple of pieces of plywood, four small bolts, and a robust amount of drywall screws.
It’s a real beauty, a true monument to the craft of the toolmaker!
But, it has a beast-like grip, minimal to no vibration, and big, long jaws. Plus, I only spent about 1 hour making it. I can file the entire side of most saws, without having to reposition the saw plate. The jaws are about 20 inches long, so bigger saws require some repositioning.
So, in a working shop where efficiency and economy rule, this hideous little champion can’t be beat.
Perhaps I’ll build my beautiful, finely crafted version another day, and place it in my hand tools only hobby shop, or maybe I’ll see the inner beauty of Frankenstein.

Engaged with the monster
Side note: I’m fully rooted back in Montana, and am in full swing.
Also, I wanted to give a special thanks to a client, Fred, whom graciously sent me some nice tool books to show his appreciation. Much appreciated Fred, I’ll try to make the next saw extra special for you.
KLR