Making a More Ergonomic Jeweler's Saw
© Brian Meek
V1.3, All Rights Reserved
One of the basic definitions of 'tool' is that which extends the capacity of the human body, or that which becomes an extension of the hand.
The saw-frame is one of the most basic tools of the metalsmith; with it we can form shapes, pierce out forms and create linear decorations. We can use it to file, separate, and generally impose our will upon the metal.
My original 'FrankenSaw'. Still my favorite saw, and now an old friend.
Unfortunately, as most of us are well aware, the jeweler's saw-frame, our most basic, and often most personal tool, leaves much to be desired in terms of personal ergonomics. My main objections to them are two. First, and perhaps worst, they usually have handles that are quite small in diameter, so those of us with hands larger than those of a child are required to expend a great deal of extra energy in wrapping our hands tightly around them. After several hours of work, this can lead to hands that are cramped and generally painful while working. As anyone who works with stress injuries to the hand can tell you, the easiest way to reduce hand stress it to reduce grasping power. Making the handle both larger and custom fitted achieves this admirably. The tight grasp caused by undersized handles also causes two problems with accurate sawing. In an ideal world, the jeweler's hand should be wrapped loosely around the handle, effectively just guiding it up and down. But since the handles are small, we—or at least I—have to grab quite hard, just to hold on. This tension makes it difficult to guide the frame accurately: every little jiggle tends to manifest itself in the sawn line. There was also the problem of grabbing the round handle at the same orientation every time. For years I thought my saw-blades all cut 10 degrees to the left, but it turned out that I was just holding the frame wrong.
The other problem with stock frames the physical one of balance and momentum. The standard saw frame is quite badly out of balance, and this becomes more and more obvious as the throat depth deepens. What I'm talking about is that 'kicking' sensation that large saw-frames exhibit that makes them so hard to handle accurately. It also happens to little frames, it's just that we've grown accustomed to it, and at that scale, have the muscle power to compensate for it. What's happening is that the center of gravity of the saw is somewhere up in the frame section, which is hanging back over the wrist. As a graphic example, take any large saw-frame in the shop, and try to balance it by placing the rearmost of the uprights on an extended finger, or a pencil held in a vise. Notice that the frame balances with the pencil somewhere about an inch from the handle or so. (on larger frames; closer in on smaller ones.) That point is the center of mass; the point where there is equivalent mass on either side of the pivot. That is also the point it will try to rotate around during any activity that involves a change in motion. ("...objects in motion will tend to stay in motion....")
Thus after a downstroke with that frame, when the downward motion is finished, and it is time to stop and go back up, the frame will attempt to keep going down, and all the extra weight out beyond the center of mass will act to force it to pivot backwards. The hand becomes the actual pivot point, but the thrust expresses itself as backlash, driving the top of the frame down toward the wrist, until the hand applies power to stop it. The same thing happens in reverse at the top of the stroke, when the out of balance mass wants to keep going up. There isn't a whole lot of energy here; we've all become accustomed to it, but it becomes very evident when using a big frame, sawing quickly, or worse yet, doing both. In a perfect world, the center of mass should be directly in-line with the sawblade, so there's no kick, either way.
The reason for the intro physics lesson is simple; with a modest application of modern plastic technology, we can cure both problems in about an hour.
A selection of my FrankenSaws. No points for guessing which one I use most.
Notice that the handles on the other two are much larger, and the finger grooves are not as deep.
I didn't grab as hard. These saws are more comfortable in the hand, and balance better because there's more Fimo.
The red/silver handle is the one I take to workshops: all my traveling gear is flashed red-silver-red.
This is a great way to identify your tools at a glance. (so long as you pick other colors.)
First I would like to express thanks to Ralph Hargate at City of London Polytechnic for the comment that sparked off this idea.
The remedy is simple; apply a little bit of the plastic 'clay' that has been all the rage among the hobby crowd lately to the handle, mold it to your hand, fire it and when it cools, you'll have a saw-frame which is much better balanced, and fits your hand perfectly.
Purchase roughly two little blocks of "fimo" or which ever of the plastic 'clays' your local hobby store stocks. Fimo is middle of the road in final hardness. Cernit and Modello are harder, the Sculpey series is softer. The trade off is that they're also easier to knead. I've had a Fimo handle on my saw since 1991, and it's holding up beautifully, even in the face of being used as an impromptu soft mallet on occasion. I've received feedback that several people have attempted to use jeweler's Jett-Sett compound to do one of these handles. Jett-Sett molds while at roughly 200° F. That's really rather hotter than you want to be hanging onto for the length of time required to get the handle molded properly. The fimo class thermoplastics all mold at room temperature. They're much easier on your hands, and safer. Please use those instead.
Take your saw-frame as far apart as you can. You'll be putting it in an oven at around 350-450° F. The heat could possibly be bad for some of the parts. Ideally, only the handle and the rearmost upright should go into the oven. Take this time to also rig some sort of a trivet to hold the saw so that no part of the handle hits any part of the oven, or of the cookie sheet this will all probably be resting on. Knead the plastic together, until it is quite soft. Now either roll it into little coils about the diameter of a finger, which then wind around the handle of the saw, or roll it into a sheet, which you then wrap similarly.
(as an aside, get the best saw-frame possible before you do this: you're going to be using this frame for a long time.)
Now grab the plastic wrapped handle in whichever hand is normally used to saw with. Try to make as natural a grip as possible, with the upright of the saw pointing straight back down the wrist. I have done several of these handles on my own saws, and have found that the most comfortable grips are the ones where I didn't grip as hard, so that the grips are slightly larger in diameter, and have finger grooves that are not as deep.
As you gripped, there should have been plastic squeezed out of both ends of your fist. Keep the hand gripped, and use the other hand to pack that plastic back in along the top and bottom of the grip. Try to set it up so that most of the squeezed plastic comes out the bottom, and then pack it back, and mold it to fit the contours of the bottom of the fist. After you're satisfied with the fit of the handle, throw it in the oven, following the instructions that came with the plastic, and bake it until hard.
After it cools, you'll have a saw-frame that fits your hand perfectly. A saw that you don't have to clutch to use, and that you will always grab exactly the same way, every time. (And that no-one else in the shop will borrow.)
The plastic also adds enough mass to substantially reduce the out-of-balance effect on the saw. It's still not perfectly in-line with the saw-blade, but it's generally close enough. The difference is unbelievable. My 4.5 inch frame rides like it's on rails. It's one of those little problems that you never notice, until it's fixed.
Try it, you'll like it.
(and if you don't, you can always take a knife and cut the fimo off.)
Two views of the grip of the original FrankenSaw.
The grip of FrankenSaw MkII. Note that the handle is larger, and the finger grooves not as deep.
This gives a more relaxed hand position, and makes it easier to use the saw with different hand positions if necessary.
(This saw is more comfortable in the hand, but I've been using the old one so long I'm not changing now.)
Photos showing the balance point of FrankenSaw 1, and the alignment of the saw with the hand & forearm.