Circle Cutting Guide
Review
By Dean Bielanowski
As the saying goes, there are many ways to skin a cat. Well, to be
honest, I'm not sure where that saying came from or what it was based on.
Regardless, the saying remains true in terms of cutting circles in wood; there
are many ways to do it. You can either use a hand saw, a jigsaw, a bandsaw, a
router or even a table saw, and I am sure there are even more ways too!
Naturally, some methods may require further sanding or work to bring the cut
piece to a true circular shape.
When trying to cut a circle using a power tool or stationary machine
however, often a circle cutting jig is needed. These can be either shop made,
or commercially purchased jigs. Having a need to cut a few circles myself
recently for a project, I grabbed a Torquata circle cutting guide to help
assist with the cutting process.
Torquata Circle Cutting Guide
The Torquata guide is really a simple kit system, based pretty much on
the same adjustable pin system you could make yourself as a jig in the
workshop, but if you are like me and prefer the commercial made jigs, then this
one is ready to use, and quite flexible, as it can be used on several different
machines, whereas many shop-made designs might only be made for a specific tool
and cannot be readily converted for use on another. This particular guide is
designed for use on stationary saws such as the bandsaw, radial arm saw and
table saw. I don't own a radial arm saw, so I tested it and based this review
on using the jig on my bandsaw and table saw.
The Circle Cutter is designed to cut circles from 3 inches up to 4 feet
in diameter. If you want to cut larger circles, you will need to make your own
circle cutting jig as this one reaches its limit at the 4 foot mark out of the
box.
Assembly is quick and painless, and basically involves tapping a few
connector pieces into the steel channel sections, and adding a hex nut into one
channel to attach the pivot pin. A base clamp is also included, as are
instructions for assembling it, but mine came pre-assembled out of the box, so
setup time was only about 5 minutes in total. A bag of assorted screws,
double-sided tape and other bits and pieces are included and used for special
mounting situations (which I will outline shortly).
How Does It Work?
Long time woodworkers can probably figure out its operation just by
looking at the jig assembled. Everything is pretty straight forward actually.
I'll start by explaining the process of cutting a circle out using the table
saw and the circle cutting jig.
Whoa! Hold your horses! Cutting a circle on a table saw! Are you crazy?
Despite some common "myths" (I guess you could call them), cutting circles on a
table saw is indeed possible, and can be done safely too with the right
procedure and appropriate jig.
To set the jig up on the table saw, you firstly place the base clamp in
the miter slot of the saw, and align it with the arbor of the table saw. The
base clamp fits into position via a hex head screw which screws outward from
the base clamps edge to lock in place against the edge of the miter slot. It is
designed to fit standard 3/4" x 3/8" miter slots but there is some tolerance
either way for slightly smaller or wider miter slots. The main channel (which
is the longer piece of channel) then slides into the groove in the top of the
base clamp, and is secured by two screw and washer assemblies on either side of
the channel with the support arm channel (the shorter of the channel lengths -
which is actually made up of two joined channels) situated close to the blade.
Perhaps one of my criticisms of the base clamp is that it can be difficult to
lock it firmly enough in place, as the adjustment screw sits under the clamp,
and when mounted in the miter slot, the adjustment screw is not really
accessible. The best you can get is a solid friction fit, and for most tasks,
this should suffice. However, if you have a couple of miter slot stops which
can be secured into the miter slot on either side of the base clamp, you can
really lock the base clamp and jig into the slot very securely.
Now, depending on what diameter circle you wish to cut the procedure to
use with the jig differs. For circles up to 12" in diameter, the pivot pin
(located in the main channel) is secured as close to the support arm channel as
possible and secured in place. The main channel then slides on the base clamp
left or right (closer or further) from the blade to adjust the radius of the
circle being cut. For circles larger than 12" in diameter, the support arm is
moved and positioned as close to the base clamp as possible (i.e. away from the
blade) and secured. The pivot pin is then moved along the main channel to set
the desired radius for the jig. There are special support situations for
circles less than 6" in diameter (where a special nylon knob is attached to the
workpiece to keep fingers away from the blade, and for circles larger than 24"
in diameter where a support leg is attached to the end of the main channel so
it isn't overhanging the edge of your saw table without support from
underneath. Instructions for both of these situations are included in the
documentation.
A 1/4 hole is drilled in the blank to sit over the pivot pin. A smaller
pivot pin is also include so your pivot pin hole doesn't need to be drilled all
the way through the workpiece. If you do not want to drill any pivot pin holes
at all, the package comes with a plastic mounting plate with a 1/4" hole in the
middle of it. This plate is attached to your blank with double-sided tape, and
then the mounting plate sits over the smaller pivot pin and allows the blank to
be mounted without drilling or marring the blank. This is handy if both sides
of the cut circle will be readily visible.
Once the blank is mounted to the pivot pin (by whatever means you choose
from the available options) it is time to cut the blank. On the table saw, it
is recommended that only 1/16" of an inch is cut with each rotation of the
blank, so the blade is set 1/16" of an inch higher with each subsequent
rotation. Obviously, it will take a few rotations to cut all the way through
thicker blanks, but it does do the job well, and often with little cleanup
required afterwards. Where required, and particularly if the blank is sitting
up above the saw table by any margin, a filler piece of scrap material the
width of the gap between the blank and table surface should be clamped to the
table to support the blank underneath so it does not tilt onto the blade and
affect cut accuracy or compromise safety. I made several blanks using the jig
on the table saw, and each worked out fine. Just be cautious of where your
hands are all the way through the cutting process as the blade is hidden under
the material for all but the last cutting rotation, and if you take your time,
you should be able to make circle cuts safely and cleanly on the table saw
using the Torquata Circle Cutter jig.
On the bandsaw, setup is pretty much the same in terms of mounting the
blanks and setting up the jig for the different diameter circles as it is on
the table saw. For smaller bandsaws, the bandsaw table might not be as wide
from the miter slot to the edge, so additional support from the ground up to
the jig via an attached support leg (user to make and use) will be required.
Cutting a circle on the bandsaw is quicker than with the table saw, as you can
cut the circle in one pass. Use a smaller blade (1/4" or 3/8" blade) for best
results (as these blades are designed to cut curves). More cleanup work is
required after cutting on the bandsaw as the blade leaves much more obvious
teeth marks around the edge of the circle. Of course, if you have a decent disk
or spindle sander with a 3/4" x 3/8" miter slot, you can use the same circle
cutting jig as a sanding jig to give you a constant radius distance from the
sanding surface, and by rotating the piece on the jig, you can sand to a
perfect circular shape. This method of sanding also makes it possible to rough
cut a circle using a jigsaw and refine the shape on the sander.
Concluding Thoughts
While it is possible to cut circles in numerous different ways, I do like
using this jig, mostly because it can be readily attached and removed from the
saws without much fuss. There is no need to build a large, heavy sub-table for
circle cutting tasks on the bandsaw, and no need to continuously punch nail
holes into a sub-table for the pivot pin. Plus it is light and easy to store,
not taking up too much storage room. Granted, you could make your own jig
without too much drama, but if you wanted to make it using metal components, or
T-track accessories etc, the cost could add up quite fast, and at just under
AUD$44, the adjustable circle cutter is quite cost effective, plus offers the
benefits and features to cut circles without drilling or marring your blanks.
Unless you are cutting circles every day in your shop (and would probably
require a jig that is more permanently fixed or solid, the Torquata Adjustable
Circle Cutter should certainly meet the needs of occasional circle cutting
tasks...
Now, I have to get back to circle cutting my third lazy susan!
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