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Make a tool holder
by Dave Eaton
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Many useful woodturning tools are only available in the form of
a "bit" or "tip" rather than a fully handled tool. A couple that come to
mind are the Wolok or Martel Hook Tools and standard Two Flute End Ball
Mills which are used
for end grain hollowing of open forms like boxes and vases. Additionally for
closed form hollowing square carbide tool tips can be used such as David
Ellsworth shows. One reason these are sold as bits form is they are made
of extremely hard steel which prohibits them from being long in length. Since these
tool tips are usually not supplied with the supporting "holder" needed to use
them for turning, one must either purchase a suitable holder for around
$25 or craft one themselves.
The latter is the subject of this article. You need
only rudimentary metal working skills and equipment to take a round steel
rod and adapt it for such use. The cost of making such a tool is
considerably lower than a purchased product and is nearly identical when
complete. The holders made as shown cost about $7 each.
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First, let's start by understanding the problem. The
tool bit is typically a piece of metal with a special grind on it
which terminates in a short one or two inch straight shaft for mounting such as
the Wolok Hook Tool shown here. If the bit were not held firmly by the rod
as shown it
would be of little use. Once we have a steel rod holding the small bit
we are then able to use the tool just as it is or, as is often done,
with the other
end of the rod inserted into a wooden tool handle such as would be
typical of any other
woodturning tool. |
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Hook Tool inserted into rod
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Even though the rod is simply a length of steel with a
hole drilled into the end it can be a little tricky to fabricate for the
ordinary woodworker who lacks access to a metal working shop. Let's see
how we can easily machine one of these rods using tools most woodworkers have access to. First of course, you need to obtain a
suitable length of useful diameter steel rod. Choose either cold rolled,
mild, or galvanized steel rod as it is reasonably soft enough to machine
easily. This material is readily available at home centers like Home
Depot or Lowes, Ace hardware etc, or can be purchased from MSC
Industrial Supply, Grainger, Enco Tools and more.
The diameter of the rod can be critical. It must be large
enough to allow a hole size in the end to accommodate the bit you will
insert and rigid enough to withstand bending or vibration when working
at full depth. For hollowing to a depth of less than 18 inches, a 5/8
inch diameter is recommended. For deeper hollowing move up to 1+ inch
diameter. If I recall correctly, Mitch Wolok, who developed a hook tool,
said he can hollow perhaps 3 feet deep with a rod larger than 1 inch (and 6
ft long!) but for our discussion let's stick with 5/8" diameter rod which is
probably all we'll ever need.
Most steel rod at local hardware stores will come in a
3 foot length. This is a bit long for our needs so cut it with a hacksaw
to a shorter length. My choice is to cut it right in the middle yielding
2 each 18 inch lengths for 2 holders. You could choose 12 inch lengths
but after burying 3 inches into a wood handle your maximum hollowing
depth may not be sufficient.
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Next comes the fun stuff. Place the rod vertically into a
vise or clamp, mark the center with a marker or better yet scribe a
couple intersecting lines with a nail, awl or X-acto knife. Use a center
punch and punch the center for ease of starting the drilling.
Since there are rotational forces that will be working
on the bit when in use, it is also a good idea to add a set screw or two to the side
of the rod to prevent the bit from twisting. Some turners use
superglue for this which seems to work fine, although it makes bit replacement
more difficult.
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End of rod center punched
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An easy way to mark the side of the rod for the set
screws is to simply run a file across the side with one pass while
keeping the file held in a consistently "flat" angle. This will mark the
steel with a small shiny flat which can then be used as a reference.
Making sure the reference line is at the top, scribe marks for your
screw hole locations. The marks shown are at 1/4 inch and 7/8 inch
from the rod end, but the locations are not critical as long as you
assure that the screws will in fact make contact with the bit when
inserted. Punch these locations for drilling as well.
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Side of rod marked for set screws |
Place the rod into a drill press, up through the center
hole in the table and clamp it in place. If your rod wont fit or drill press table
has no hole then you might alternatively tilt the table 90 degrees and clamp
accordingly. I use a wood screw clamp with a "hole" in the jaws to
grip the rod. Drill a pilot hole in the rod with a spotting drill
or other, preferably small and short drill that will not wander such as
a 1/8 inch bit. A spotting drill is made specifically for this, to be
strong and not wander from the center punched dimple. Be sure to apply
sufficient cooling oil during drilling or smoke is all you will get. The
3-in-1 oil brand is suitable, even motor oil if you're desperate.
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Spot drill the center to 1/8" deep |
Once a pilot is drilled switch to the larger diameter drill
bit which will accommodate your tool bit shaft and re-drill the same hole to
desired depth. For the hook tool, since the bit shaft is 1/4 inch dia. I
use a 5/16 inch drill bit which allows for shaft imperfections but is small
enough for good support. The hole depth is about 1 inch. Don't worry if
the hole isn't straight or exactly centered either. Do your best, but
when you're using the tool to cut - the wood "will never know." This
process can be done with a hand drill if due care is taken. The results
will perhaps not be as precise but the end result will work fine.
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Drill full size dia. for bit. |
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Remove the rod and re-clamp it horizontally for drilling the
set screw holes. Again use a spot drill to prepare and then re-drill to
a size appropriate for the set screw.
A #29 drill bit is needed for 8-32 x 3/16 inch set
screws.
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Drill set screw holes
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Once drilled, tap the holes with a hand tap, using oil again,
and your almost done.
In fact the only tasks left are cleaning up and
assembly.
To ensure that the rod will fit into a hole drilled into
wood for a handle if desired, grind the back end of the rod slightly
easing the sharp edge and removing any burrs. |
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Tapping the threads in the hole
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Additionally, it usually a good idea to round the
working end of the rod a bit to prevent a sharp edge from causing injury
or scratching your work.
It's as easy as rotating the end of the rod against the
grinding wheel, raising and lowering the far end until satisfied. If a nice
shine is desired you may buff the steel or use sandpaper or Emory cloth
to bring out the finish desired.
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Chamfer the ends of the rod |
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Lastly, insert the tool bit and tighten the rear
set screw assuring it grabs the bit. Then install any other set screws. You
may need to file the heads of the set screws slightly to bring them down to
the surface of the rod, but be sure to leave enough hex socket to remove
them later. If they are too long, remove them and grind down the other
end. Congratulations - You're a machinist! |
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Finished rod with bit installed |
You can use this rod to hold many styles of bits like
these below:
- Hook Tools for open form end grain hollowing
- Ball End Mills for open form end grain hollowing
- High Strength Cobalt steel tool bits for closed form hollowing (i.e. Ellsworth)
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Sources:
M2 Hardened
Wolok Hook tool bits - <$30
Andre Martel Hook
tool bits - $40 to 90 per size
Ball End Mills - Enco or
MSC - $15
Hard Tool Steel bits - $3
1/8"
Spotting Drill - $3These below are normal
hardware store items:
5/8
Steel Rod - 36" lengths $12 at Lowes
8-32 x 3/16"
Set Screws - 0.20c
8-32
Tap - $3
#29
High Speed Twist Drill bit - $3
5/16"
High Speed Twist Drill bit - $5
3-in-1 oil or
cutting & tapping fluids - $3 |
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Make your own hook tool by A. Lacer
Info on Hook Tool
by Mitch Wolok
Finished rods and hook tools |
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Jan 2007
(c) Dave Eaton 2007 - Rights of use or
reproduction in whole or part freely allowed provided Dave Eaton cited
as source. |
