Pictured is the Pepe Tube Cutting Jig with a piece of copper tubing in place. The photo is deceiving in that my thumb is missing from holding down the thumb clamp. That's the gray colored thingy in the center of the jig. I didn't have a good way to hold the camera and include my thumb at the same time. Sorry about that.
Anyway, the jig is adjustable for length, up to 13 cm, and for stock up to 6 mm in diameter. The wood handle is obviously for hand held operation. I found this to be rather difficult for me to do, even bracing the jig against a bench pin.
A couple other things to know about the jig. By removing two screws on the saw guide ,and by using thin brass sheets (shim stock), the width of the saw slot can be adjusted for larger or smaller width saw blades.
The other thing is that everybody says you can't use the jig in a vise. Phooey! The photo proves this contention as wrong. But, there is the fact that you may have to remove the jig from the vise in order to change the setting for a different length. Only a minor inconvenience.
As you can see, the jig is firmly and safely secured in a vise, albeit a small, one inch jaw width, machinists vise. I won't say that is the only vise that will work. A small vise like that is always handy to have around. So are C-clamps! Very handy.
If there is a drawback to the tube cutting jig, it's that it can be a tad difficult with the way I've set it up to retrieve very short lengths of cut off tubing from the jig. But, a pair of sharp point tweezers or a fine point awl (aka bodkin), will do the trick. I suggest that you also have something under the jig to catch the cut off as it falls from the jig. I'm still searching for one that got away.
Now, a cautionary reminder. Very thin tubing may require some sort of support inside the tubing, or the tubing could collapse from the pressure of sawing. So a wood dowel, bamboo skewer, or a round toothpick inserted inside the tube should do the trick.
The saw cuts will produce some burring, so you can remove these with a fine file and sand paper as you cut, or do it later, whichever is easiest for you. Tumbling with stainless steel shot will remove some, but maybe not all of the burs. Remember to lube your saw blade and have the blade tensioned properly. I really didn't need to remind you of that, did I? I use bees wax. You can see a lump of it in back by the saw. It's only about 70 years old and is like the Energizer Bunny. It keeps going and going. I lube the back of the blade, not the teeth. I find it's better that way.
Why would you need one? Dunno. What can you make with one? Same length spacer beads. Any length metal beads. Within reason, of course. Danglely things for necklaces and earrings. Decorative add-ins on metal pieces. Tube rivets. Tube settings for stones. Cups for enameling on metal backing. Et cetera, and so on.
The Pepe Tube Cutting Jig is available from several on-line jewelry making supply companies. Mine was purchased from The Contenti Company. I have no affiliation with Contenti other than as a customer.
Thank you and good luck sawing whatever you saw.