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Wooden Jaw Jig as 3 page pdf
Wood/PVC Jaws article
has a better jig
Wooden Jaw Jig
Introduction and Safety
Iíve found that I can easily extend the capabilities of my
four-jaw chuck by making special purpose wooden jaws.
By using wood I can shape the jaws to whatever shape I need, and I can
grip even already finished parts of the work without marring.
I use a One-Way Stronghold chuck, but most modern four-jaw chucks are
similar enough to use the same technique.
When I first started using wooden jaws Iíd turn a disc, drill holes, and
then cut it into quarters. It was
hard to get the holes drilled accurately, particularly since each hole requires
two operations to drill and countersink.
I tried One-Wayís special
jaws bases for wooden jaws, but they were too big for most of my intended uses.
Making this jig allows me to use a consistent grain direction for each
jaw and to drill the holes easily and accurately.
Please keep in mind that the mounting power of wooden jaws
is less than that of metal jaws. A
serious catch can break a jaw away from the mounting screws.
You arenít limited to finishing cuts by any means, but do use common
sense in regards to the size, weight and balance of the work you mount with
wooden jaws. This jig will make jaws
that are up to 3 inches in radius, although I usually use about 2 to 2-Ĺ inches.
If you want big jaws, to reverse a bowl to turn the base or the like, use
the special bowl jaws or the metal jaws designed to mount wooden jaws.
Measuring Mounting Hole Separation
The first step in making a set of wooden jaws is to
determine the separation of the mounting holes.
Itís not easy to measure this distance directly, especially on the base
jaws, because theyíre threaded. Itís
much easier to measure the distance indirectly if you donít mind doing just a
Itís more accurate
if you use a caliper, but an accurate ruler will do.
First measure the diameter of the top of one of the mounting screws (and
write it down. The diameter of the
mounting screws of my One-Way Stronghold is .460 inches).
Now screw a mounting screw finger tight into both holes of a base jaw and
measure from the inside rim of the inside screw and the outside rim of the
outside screw (mine measured 1.460 inches).
Subtract the screw diameter from the second measurement and you get the
hole separation (1.0 inches for my Stronghold).
You can also measure on one of the jaws.
With calipers a two-step procedure is best.
Using the inside measuring points, measure from the inside of the inside
hole to the outside of the outside hole, then measure and subtract the diameter
of one of the holes.
results will agree. If you donít
trust your caliper skills, to double check you can drill a pair of holes that
distance apart in some thin stock and make sure you can mount it on a base jaw
with both screws.
Making the Jig
The three parts of the jig are the Base, the Frame, and the
Slide. All three parts can be made
out of whatever scrap you have laying about, but I recommend ĺ inch plywood for
stability. The only measurement that
needs to be exact is the difference between the width of the Slide and the
inside of the Frame. Everything else
can be altered to suit what you have on hand.
The function of the Base is to hold the Frame and to allow
the jig to be clamped to your drill press table. Cut out a piece of wood about 8
inches wide and 20 inches long or a little longer than your drill press table is
The function of the Frame is to align the Slide in two
positions that are the same distance apart as the mounting holes on your chuck.
Cut a piece of ĺ inch plywood that is about 8 inches long and 11 inches
long. Draw a line parallel to and
1-Ĺ inches below the top, and another parallel line 5 inches below the first
line. Now draw a line that is
perpendicular to the first two lines and that is 3 inches to the right of the
left side of the Frame. You now
should have a rather fat ďCĒ drawn on the Frame.
Cut out the inside of the frame.
You can use a band saw, but cut slowly so that it will be reasonably
accurate and plan on going back to square up the corners.
Now fasten the Frame to the Base.
The left hand edge of the Frame should be about 7 inches to the left of
the center of the base. You can use
screws, nails, glue or any combination.
The function of the slide is to hold a wooden jaw for
drilling. Cut out a piece of ĺ inch
plywood about 4 inches wide (or so the difference between the width of the Slide
and the opening of the Frame equals the hole separation of your jaws) and 8
inches long. Cut carefully, this
piece should be cut with square sides and corners.
Measure 1 inch to the right of the lower left corner, and draw a line
that angles up 45 degrees to the right.
Now measure 1 inch to the left of the right corner and draw a line that
angles up 45 degrees to the left.
Carefully cut out the resulting triangle.
Set the Slide into the Frame and make sure it fits up against the left
edge of the ďCĒ and that the corners allow it to move all the way to the top and
to the bottom. Now check how much
travel is allowed. It should match
the hole separation of your jaws. If
the travel is too little, you can file, plane, or sand a little from the bottom
of the slide. If the travel is too
much, you can shim it with paper or thin cardboard. Before making jaws you can
test the jig on a triangle of ľ inch plywood and see if the resulting holes
match the mounting holes on your chuck.
You can use any wood to make jaws.
I usually use maple because itís easy to turn, strong, and I have a lot
of it about. I cut a board so that
the width of the board is the radius of the jaw I want, usually 2 inches.
Then I cut this board into triangles.
I use a sliding miter jig on my table saw, but you can use a chop saw or
a band saw, as long as the result is a consistent set of right angle isosceles
triangles. You only need 4
triangles, but why not cut more while you have things set up?
Pick one of the triangles and draw a line that bisects the
90 degree angle to aid in orienting the jig.
Your holes will lie along this line.
You can vary the location of the holes depending on how far you want the
jaws to open and whether youíll run anything through the center.
To start, measure Ĺ inch down from the 90 degree angle along the
bisecting line and make a mark. Put
the jaw into the slide. Make sure
that the jaw is all the way to the top of the Slide and that the Slide is all
the way to the bottom and against the left side of the Frame.
Mount a drill bit in your drill press that is slightly
larger than the diameter of the jaw mounting screws your chuck uses.
I use a Ĺ inch bit. Position
the jig on your drill press table so the drill bit is centered on the mark.
Clamp the jig in place on the table.
Check again that the jaw is to the top of the Slide, and the Slide to the
bottom and left of the frame and that the drill bit is still centered on the
mark. Take the jaw out, and set the
drill stop so that the bit stops about ľ inch from the frame.
You may have to adjust this to fit the length of your chucks mounting
Turn on the drill press, and put the jaw back in the Slide,
making sure (at the considerable risk of repeating myself to much) that the jaw
is at the top of the Slide and the Slide at bottom left of the Frame.
Drill the first hole. Now
slide the Slide to the top left of the Frame (making sure wood chips donít
prevent this) and drill the second hole.
Repeat this for the other three jaws.
Now change the drill bit to one a bit bigger than the
thread diameter of your chuck mounting screws.
I use a ľ inch bit. Adjust
the drill stop so that the bit drills a little ways into the Frame.
If you have to adjust the table height at this point make sure the drill
bit is still centered the same. Now
using the same procedure drill the second set of holes in all the jaws.
You can, at this point, cut the corners off the jaws on your band saw or
you can turn them off after theyíre mounted on your chuck.
Mounting and Shaping Jaws
Mounting the Jaws
To mount the wooden jaws, first take off whatever jaws are
mounted on your chuck and set the mounting screws aside.
Check to make sure that enough of the screw extends through the wooden
jaw to fasten securely. Align a
jawís holes with the mounting holes on a base jaw, and screw one mounting screw
in loosely. Then start the other
screw. If you canít start the screw
straight in, stop. Youíll really
regret stripping the threads on your base jaw.
Enlarge the hole in the wooden jaw a trifle with a round file and try
again. Once both screws are started,
tighten them both securely. Repeat
for the other three jaws.
Shaping the Jaws
Once you have all the jaws mounted, screw the chuck on to
your headstock. The jaws will hold
better if the radius you cut into the jaw matches the size piece you want to
hold. However, you want to have some
adjustment left in case some of your pieces are a little oversize.
The chuck may not hold itís setting if itís not gripping anything, so you
canít just open it up. Instead clamp
a piece of scrap wood about ľ to Ĺ inch thick in between.
Then turn on your lathe, and turn the jaws.
For safety youíll want to turn the perimeter round first, and probably
put a radius on the outside edge.
If you want to grip a disk, just turn a recess in the jaws.
A depth of 1/8 to ľ inch will probably be fine, and wonít put you in any
danger of hitting the mounting screws with your turning tool.
. To grip a flat square, such
as for a rosette, turn a recess that intersects a set of mounting holes, then
put the points of the square in the holes and tighten.
If you want to mount a tenon or dowel, mount your drill
chuck in the tailstock and drill the appropriate sized hole.
If you use Forstner bits youíll get a truer hole, just be careful you
donít hit the metal chuck. To grip a turning square just drill a round hole like
you would to grip a dowel or tenon
If you want to grip spherical or hemispherical items (such
as tippy-tops or scoops) you may want to make thicker jaws.
You donít need to try to mimic the spherical or hemispherical shape, just
turn a cylindrical recess. The
recess should be a little deeper than the hemisphere.
You add a lip at the front of the recess for a more secure grip.
At the 2000 AAW Symposium I watched Rude Osolnik turn a
bracelet, holding the stock between a wooden pressure pad attached to the
headstock and tailstock. He then
turned what he called a ďmoon-roarerĒ with the left-over center piece.
Itís a simple toy, a two hole wooden button with a string looped through
it. You hold the loop at each end
with the button in the middle, swing it around to wind up the string, then pull
rhythmically. When it gets to going
fast it makes a roaring sound. No
batteries are required and kids can work it at a younger age than tops.
Pressure turning leaves a central area unturned, so I made
a set of wooden jaws to make the toy.
I clamped ľ inch thick piece of scrap between the jaws and turned a 2 Ĺ
inch recess about 1/8 inch deep. I
found a piece of Ĺ inch thick Padouk, roughed it into a 2 Ĺ inch circle on the
bandsaw, and drilled a pair of 1/8 inch
holes about ĺ of an inch apart in the middle of the disk.
I mounted the disk in the jaws and turned the front half of the rim true
and cleaned and recessed the face.
Then I flipped the disk over and repeated it on the back side.
Using the toy with just string loops (actually I used nylon
cord) pinched my fingers a bit, so I decided to make some handles.
One could turn handles between centers of course, but this is an article
on wooden jaws, so I clamped a 1/16 inch thick scrap between the jaws and used a
3/8 inch forstner bit to drill about 3/4ths of the way through the jaws.
I cut a 1/2x1/2x6 inch piece of Padouk on the bandsaw, and drilled two
pairs of 1/8 inch holes, then clamped it in the center of the jaws.
I brought up the tail stock for support and turned the handles, parted
off the first, cleaned up the end of the second, then parted it off too.
If you share my addiction to good coffee as well as the one
to turning, you might like making this combination scoop and bag closer.
I hate those little covered wire closers that come with most coffee bags
because they never miss an opportunity to fall off and get lost.
You probably know the scene; you retrieve your stash of the good stuff
from the freezer, fumble with the closer, search for where you spouse has hidden
the coffee measure, and then canít even reach down far enough into the bag when
you find it. This scoop/clip solves
all those problems (I should add that my wife doesnít consider any of the above
to be problems, focusing instead any specks of coffee that might get brushed off
the counter to cling to the sawdust already littering the floor).
The clip allows easy opening and closing of the bag and wonít flutter to
the floor. The scoop is always right
there where you need it. The long
handle lets you reach way down in, and if that isnít enough you can cut off the
top of bag and still seal it just as well.
To make the jaws for this jig, find or glue up some 2 inch
stock, then cut, drill and mount them as usual.
Clamp a ľ inch spacer in between the jaws and turn a 2 inch diameter
recess a little deeper than 1 inch.
You can add a lip on the rim for extra security.
Take two adjacent jaws off of the chuck and cut about 3/8 inch off what
will be adjacent sides on the band saw to make room for the handle of the scoop.
To prepare stock for the scoop/clip, glue two 1x2x7.5
pieces together with a paper joint between their faces.
Give the glue a day to cure unless youíre lacking excitement in your
life. Trim the ends square, then
mount it in the regular metal jaws of your chuck.
You can get more details on turning scoops in Richard Raffanís Turning
Projects. But briefly, turn a 2
inch sphere on the end, whether you use a template or a layout system is up to
you, but do make it accurate, as any irregularities will be painfully obvious
when itís hollowed out. Turn
the handle to a shape you like, but leave the handle where it joins the sphere
fairly fat for strength. Once youíve
sanded it smooth and parted it off, split the paper joint.
Remount your wooden jaws on the chuck and mount the scoop
in the jaws. Hollow the inside of
the hemisphere, being wary of that 5 inch handle swinging about.
You may want to make a cardboard template so you neither cut through the
bottom nor leave it overly heavy.
Once the hemisphere is hollowed and sanded, remove the
scoop/clip from the chuck and clean up the paper joint.
Drill a 1/8 inch hole though the handle about ľ inch from the edge of
hemisphere and use a straight edge to lay out cutting lines from the center of
the end of the handle tangent to the outer edges of the drilled hole.
Then cut along the lines. A
scroll saw is better, but you can also use a bandsaw.
If the slot tapers it will clamp the bag better.
Round the inside edges of the end of the slot so that it will slip over
the bag easier. Then sand the inside
of the slot and apply a food safe finish if you like.