The Gramercy Tools Bow Saw - 2
document on design considerations explains how we arrived at
our production design. This document details just a few additional notes
on important items to consider if you are building your own saw.
The Gramercy Tools design is what we would consider the optimum for a
general purpose turning saw. Historically every trade used slightly different
versions of the saw to meet their own specifications. That said, we think
you can have a lot of fun playing with the design and making a frame that
suits your needs. You can also make multiple frames for one pair of handles,
multiple stretchers for one frame, or a different toggle for each day
of the week, if you like.
Safety is really important. Always wear eye protection. You never know
what might happen and it's not worth the risk.
Our shop drawings are available on our website in Acrobat .PDF format.
You will need to download
to read and print them. Make
sure you deselect the Acrobat printing option "fit to page"
(which is the default when printing the plans, otherwise they will be
reduced in size.) In order to create full - sized templates the plans
are formatted to print out on 8 1/2" x 14" paper. On sheet 4 of the
drawing we have provided a photoscale for you to verify that your printer
is not resizing the drawings.
- The material specification HICKORY is, of course, merely
a suggestion. Historically, boxwood and beech were widely used.
Any reasonably strong, clear, straight grained wood should suffice for
a frame, but the strength of your saw depends largely on the type of
wood you use. The cheeks will be under pretty high stress and if there
is a flaw in the wood, or if you over tighten the saw, the cheeks can
crack, possibly leading to parts flinging about.
- Gluing the pins is a fairly straightforward operation. The
two most important points to remember here are (1) that the handles
must be bored with a tight, 1/4" diameter hole, and (2) the glue
must dry with sufficient thickness and hardness to utilize the positive
interference provided by the pin's grooves and flat. Aliphatic resin
wood glue or polyurethane adhesives will probably work just fine, but
you can't go wrong with a good 2-ton epoxy. Mix well and serve.
- Our design shows curved mortise faces and tenon shoulders.
As our design document states, we did it for flexibility. Since our
saws are made on automated production machinery it's pretty easy for
us to do. If you are working by hand, squared up mortises, tenons, and
faces are the way to go.
- The slots in our pins are about .030" wide. If you choose
to use a wider, thicker blade you may find you need to grind the ends
of your blade thinner or widen the slots with some folded sandpaper.
TENSIONING AND OVER-TENSIONING YOUR SAW - READ CAREFULLY
- We use braided fishing line to tension our saws. Its quite
strong and doesn't stretch. Tie it in a big loop and then wrap the tops
of the cheeks. Use enough to get it around about eight times. That way,
when you insert the toggle, you'll have at least four strands on either
side. The first time you tension your saw, do it slowly, checking your
construction for weaknesses or hidden flaws with each twist of the toggle.
Our toggle design offers considerable leverage with which to tension
your saw. Once you've reached sufficient tension for comfortable sawing,
STOP. While it is always possible to over-tension and break a bow saw,
it is especially possible to break a new saw. Read on.
- DO NOT rely on the difficulty of turning the toggle to gauge the
tension of the blade. This can be highly deceptive. We've found
that the blade tension on a pair of identical saws can be exactly the
same, but moving the toggles can feel effortless or impossible depending
on the thickness of the cord and the design of the toggle. The correct
way to tell if your saw is properly tensioned is by using it. A properly
tensioned saw will cut smoothly on the push stroke with very little
give in the blade. However, no amount of tensioning will prevent a thin
blade from twisting in the middle as you turn it into a cut. To avoid
twisting the blade when you saw a curve take long full strokes, and saw through the curve.
- Bow saws take time to mature. To greatly increase the life
of your saw, loosen it by one or two turns of the toggle when you are
finished cutting. The cheeks will get a chance to rest and not become
permanently bent. Over the first few weeks of using your saw you will
get a feeling for the right amount of tension that works for you, your
saw design, and your wood.
Please click the links below for more information and to order parts and saws.