When we endeavour to introduce a new tool, the first
consideration is what the optimum design for the tool should be. Though
it might be tempting, we do not want to slavishly
copy an old pattern. This is because one generally does not know enough
about the context in which
the design arose or exactly what the tool was originally used for. Sadly,
too many designs have been
"dumbed down" over the years, mostly because of cost. When we
saw that there was a need for a really great turning saw, we wanted to
make sure that we understood the classic saws’ engineering so as to reproduce
only their best features.
First, a bit on terminology. Any saw with a blade tensioned
in a frame is generally referred to as a frame saw. To this day,
European woodworkers use frame saws of around two feet long, with wide
blades to do all their main cutting of boards. In the English and American
traditions (after 1700 or so) woodworkers used handsaws for those tasks,
and a narrow-tensioned blade in a frame saw only for cutting curves. These
smaller saws are typically called either bow saws or turning saws. Very
small versions with blades of around 6 inches are known as coping saws,
and are naturally used for coping joints and other intricate work. The
frame consists of a pair of mortised cheeks held apart by a tennoned
cross-member called the stretcher. The hardware, or pins,
hold the blade in the cheeks and also provide a mount for the handles.
Finally, the tension on the blade is kept by a twisted cord, a Spanish
windlass type of traction device kept from unwinding by the all-important
toggle. The typical full-sized bow saw has a distance between the
cheeks of about 8 -16 inches - typically 12 inches. This is the type of
saw we wanted to reintroduce.
We looked at every bow saw we could find, yet, there
are very few bow saws with a known history that have remained unchanged
from a documented era of production. Two saws in particular
fit that bill: one in the Seaton Tool Chest in England and another in
the Duncan Phyfe Tool Chest at the New York Historical Society. We also
looked to the bow saws in our collection, including an interesting one
from the late 19th century.
The task at hand was then to understand why each part
of the saw was built the way it was.
The Blade
The blade on all the saws we looked at was a ¼"
wide band, held to the frame by a hole drilled into the blade and pinned
with a loose pin or a short nail. All the modern bow saw makers we know
use lengths of band-saw blades.
We hated the modern blades. What works for a powered
band saw is usually too aggressive or too dull for a hand saw. They are
almost always too wide as well, which means you can’t cut a really tight
circle. That said, it’s not so easy to drill a centered, 1/16" hole
on a blade that is much narrower. The antique saws had blades that were
also ¼" wide, but only at the ends for drilling the pin holes, the
part with the teeth was considerably narrower - making for a 3/16"
or 1/8" wide blade, with the gullets of teeth moving to the centerline
of the blade. These dimensions give a tighter turning radius.
We thought about re-grinding the backs of band saw blades
to create narrower blades, but modern band saw blades are more brittle,
and we don’t like having the line of teeth off-centered.
Also, changing a blade fastened with loose pins can be
a pain the neck. You need to knock out the pins without dropping them,
and that’s no fun. Then we had an idea; why not use coping saw blades?
They’re narrow, inexpensive, and since the cross-pins are already installed,
you can just hook them into the frame.
As far as we know, we are the first company to offer
12" coping saw blades. They work like a charm! They’re even narrower
than most early turning saw blades, so you can saw very tight radii (just
like a coping saw), but with a longer, faster, and smoother stroke and
switching out blades is trivial. Problem solved!
There is, of course, the question; should the saw cut
on the pull or push stroke? The advantage of saws that cut on the pull
stroke is that the blade stays in tension, but in a frame saw the blade
is in tension anyway and by pushing you get a lot more power. We tested
both ways many times and with the right blade, pushing seems to work much
better for most applications.
The Pins
The next problem was fitting the blade to the frame.
Some more primitive bow saws used wooden fittings, but we felt that the
cross-pins would eat at the wood over time. All the professionally made
bow saws we examined used brass fittings. No problem!
We machined a ¼" brass shaft with a slot and a hook in it. We also
decided to include a regular hole so you could use old-style or wide blades.
The pin has a shoulder machined in it eliminating worry about constant
tension pulling the brass out of the handle.
Another design issue: how to attach the handle to the
brass? Some modern saws use an obvious solution – cross-pinning the handles
to the brass. It’s not that hard to do, but we wanted to offer a kit that
could allow everyone to make a saw. That meant adding cross-pins to the
kit, and the need to locate and drill through metal and wood rounds together.
This is a real problem if you don’t have the right tools. Gluing the hardware
into the handle is simple enough, but brass doesn’t readily stick to glue.
So, our ultimate solution was to cut some grooves in the shaft and then
file a single flat. When the glue hardens in the handle, it catches in
the grooves to prevent pulling out. Glue on the flat prevents the brass
from turning in the wood. With the tension on the blade taken firmly by
the brass shoulder, the glue doesn’t even have to be very strong.
Note: Holtzapffel’s, great 19th century
English compendium of tools and craft, illustrates a turning saw with
loose pinned blades, but a hooked pin is on only one side, "so that
the saw may be removed sideways from the one handle, and allowed to move
as on a joint upon the other, a provision that is often turned to a useful
account." We have no evidence that this design was ever manufactured
in the 19th century.
The Handles
How big should the handles be? Why are the handles
the way they are? Is the bigger handle on the old saws really too short
for a modern hand? There is a common thought that woodworkers today have
bigger hands so the handles need to be a little bigger than what’s found
on an antique. But how much bigger? A frame saw has two handles: a short
and stubby one, called the toe, that is farther away from the user,
and a closer one, which is bigger in all respects and used by the hand that
pushes the saw.
Then it hit us---The toe is only really used to turn
the blade in relationship to the cheeks. You wouldn’t normally hold on
to it while sawing.
The handle is where all the action takes place and here
is where understanding how traditional saws are used is helpful. All western
saws (and planes) are used with the forefinger extended, like gripping
a pistol. It gives control. What happens when you extend
your forefinger so that it rests on the frame of the saw? First of all,
you need a short enough handle to bring your hand close to the frame,
but in use, we got all the control that we needed to cut fast, accurate
curves. It was really something. On some early saws we noticed a slight
concavity in the cheek, next to the handle--- a feature that disappeared
in the mid-to-late 19th century saws. Originally, we thought
was ornamental— some over-sculpting. Now we believe it to be the saw’s
finger rest, an important feature that we chose to include on our saws.
Finally, the handle needs to be short enough to rest
in the palm of your hand. This way, your entire arm aligns behind the
saw blade and it will be easy to saw straight. Too long a handle tilts
the hand off to the side and the saw becomes harder to control.
Note: In many 20th century woodwkring instructions books, including
ones by noted authors Bernard Jones and Charles Hayward, a two handed grip is shown.
We have also noted the two handed grip in some early 20th century shop photographs. We think that
the reason for the two handed grip, where one hand is holding on much as we demonstrate and
the other hand is held over the first hand and also grips the cheek, comes from heavier saw frames of the
post 1850 era where the frame was too heavy to stay in place as the saw was turned to saw a curve. A second hand
keeps some of the weight off of the saw so you can turn it easily and it prevents the frame from twisting unpredictablely.
We find in tests that the two handed hold works but there is a loss in stroke, some speed, and
it is more awkward and there is a loss of control. However if your saw frame turns
under the weight of the cheeks it is the only grip that allows predictable results.
The Frame
The early turning saws we looked at all had very thin,
almost spidery frames. The reason for this, of course, is that the weight
of the frame will influence the cut. When you turn the saw in the cut,
you want the entire saw frame to move, so that the blade stays straight
in the frame. A beefy frame will cause the saw to feel top-heavy in use.
The handle will move with respect to the frame, twist the blade, and the
cut will meander. We wanted a thin nimble frame.
This brings us to the question of the wood. A turning
saw can be made from almost any wood that can take a little tension. The
bigger the saw, the more tension it can take. A lighter-weight wood is
preferable because of the nimbleness factor outlined above. The traditional
wood that English companies used for these saws is beech, which works
fine. However,
good quality, straight-grained beech is hard to find in quantity. In the
United States, we have oodles of great wood that is flexible, tough, and
can tolerate a lot of tension: Hickory. Our saw is made of American Hickory.
It is only slightly more than 11/16" thick at its thickest with the
cheeks thinning toward the top. The stretcher is held in place with a
shallow mortise that is intentionally over-long. The mortise exists to
register the stretcher. A little slop allows the saw frame to adjust slightly
as it goes under tension. We have seen saws where the stretcher is mortised
in to the cheeks with a curved joint.This is handy when dealing with many different lengths
of saw blade but with hickory, which is flexible, and of course with our
factory made blades, consistent length isn’t a problem. So, initially
we elected to use straight mortise joints. However, upon further thought
we realized with the extra hole our pins offer it would allow the use
of a fairly wide range of blades and we decided to go with a curved mortise
face.
Note: Bow saws in Vietnam (and perhaps other places)
are used for everything, and the saw-makers there don’t bother with mortising.
The stretch is butted to the stiles and held in place by tension. This
system works fine and greatly simplifies construction.
Another issue was where to put the stretcher in relationship
to the cheeks. We found the positioning on the old saws, with the stretcher
slightly above the midline of the frame, to function the best. This provides
a little more depth of cut without throwing the weight of the saw too
far back.
Tension
The next thing to consider: how to tension the frame.
We found several methods to choose from: (1) A twisted rope held in place
with some sort of a toggle that rests against the stretcher which is the
most popular method in the English and American tradition. (2) Catalogues
from the later 19th century show a sort of steel turnbuckle
in the middle. This appealed to our mechanical sensibilities, but otherwise
isn’t stylistically pleasing and wasn’t very popular. (3) In Europe, modern
big frame saws usually have a threaded rod with a wing nut at one end.
Again, not a very elegant solution. (4) In Vietnam, the frame is held
in tension by a wood or metal hook, and a nut at the end of the blade
holder tensions the blade. We liked the Vietnamese solution, but it complicates
the handle geometry considerably, and requires a new part for the top
of the saw.
The best solution is the twisted rope. It’s also the
lightest option, which means it’s the method that causes the smallest
momentum effect on the sawing, especially with the rope all the way at
the end of the frame. This is the method we chose, using heavy, braided
fishing line, which is pretty darn strong. Most saws we looked at had a lot of twine
of varing thickness and as you turned the toggle the toggle got harder to turn. However on examination we
found this is because the toggle was spending most of its time twisting the rope, not bending the frame.
We found that only a few loops, about 4 or so,
allowed us to tension the saw very easily without increased difficulty in turning.
The Toggle
Almost all the post-1850 catalogs show a flat paddle
intertwined between ropes that is twisted until it hits the stretcher,
and has to slide between the ropes for clearance to be twisted further.
The problem there is that it becomes harder and harder to slide the toggle
between the twisted ropes as the ropes gain tension. We have seen a couple
of recent solutions to this problem in which the toggle slides in a nut,
which keeps the rope away from the toggle and gives the toggle a protected
place in which to slide. We liked this solution, but even with the nut
in place, the toggle gets harder and harder to slide up and down as the
saw tensions. It wasn’t until we looked more closely at some 18th
century saws that we found an elegant solution. These saws use a swinging
toggle - a turned piece with a groove at the top to locate the twine.
The groove prevents the toggle from sliding, but its cross section where
the ropes cross is thin enough so that the toggle can swing easily to
clear the stretcher. It’s an ingenious solution, provided the toggle is
strong enough to withstand the compression and twisting. For this, hickory
is particularly well suited, so it was the perfect solution for us.
That all being said the swinging toggle style is almost too easy to
turn. With the sliding toggles as we said tensioning each turn gets harder. With the
swinging toggle, coupled with only a few loops of rope, rotating doesn't get harder
and even with the saw overtightend it's not hard
to underestimate the amount of tension and easily add in another twist or two.
The downside here is that you can be deceptively lulled unto overtightening the
saw until it fails. We still love this method, but as people used to sliding toggles it
took getting used to.
Summary
So, that’s how we arrived at the numerous features of
our saw. If you want a solid bow saw that captures the best of the early
19th century tradition, we urge you to consider getting one
of our original Gramercy Tools bow saws. We are pretty proud of our engineering,
and we think it’s great value.
We are also happy to give you our drawings that reflect
all our research and design if you’d like to make your own saw. We stock
kits of blades, brass and turned parts so all you need to do is the woodworking.
Even within the constraints of good engineering design there is an opportunity
to make a customized saw that has nice aesthetics. Just be careful the
wood you chose is clear, straight-grained and strong enough to take the
tension you need to make the saw work. Remember, the bigger the blade,
the more tension you will need.
Please click the links below for more information and to order parts and saws.