Esteemed Galoots,
The furnace went out on Saturday morning when I was supposed to be at
Steve Reynold's helping him with his bench project. I felt compelled to
stay home while the Furnace Guy got the ancient beast back online. So
while he sat on his bucket and pondered the guts of the Fuel Chief, I
busied myself by making a magnetic bit holder for my Yankee screwdriver.
I had been thinking of doing this for a while since I read Jeff Gorman's
account of how he did something similar. From what I remember he took a
bit holder for 1/4" hex-shank bits and ground a flat on the end of the
shank and a notch on the side of the shank for the retaining pin. My
problem was that I couldn't seem to locate a bit holder with a shaft long
enough to modify. I solved my dilemma with the realization that I could
use a 1/4" hex shank allen wrench for the raw material for the shank. It
appeared that I could remove the existing shank from the bit holder body
and substitute the shank from the allen wrench.
To backtrack a bit, a 1/4" hex shank is 1/4" in diameter from flat to
flat and just slightly more than 9/32" in diameter from corner to corner.
This will fit a middle size Yankee screwdriver, i.e. the #30 or 130
models (or the Millers Falls #61 model), which take a 9/32" shank bit.
The bodies of many magnetic bit holders are press fit onto the shanks
which are made of the same size stock as the bits. I put the shank of my
specimen into a machinists vice and tapped off the body with a cold
chisel. I measured the length of the shank inside the body (1/2", will
vary depending on model used) and added it to the 1 7/16" length I
determined I would need for the rest of the shank for my Yankee version.
I hacksawed slightly more than this from the el-cheapo allen wrench I
decided to sacrifice for a better cause. The notch on the side of a
Yankee bit and the cutout on the end are on the same side of the shank. I
decided that the notch and cutout should be cut across a corner so that
the notch would benefit from the full diameter of the shank. I used a
cutoff wheel and my Dremel to rough out the cutout on the end of the
shank. You could use a hacksaw here but you might need to cut a notch
with a 3-cornered file to get the hacksaw blade started properly. I used
a file to clean up and square the cutout and to cut the notch on the side
of the shank. I slightly chamfered the end of the new shank which would
be inserted into the bit holder body. I marked the rim of the bit holder
body to help align the new shank and then tapped the shank into the body.
This was a tight fit. The next time I do this I will drill a hole into a
piece of scrap wood to hold the body while I tap the shank in. I smoothed
the burrs from the shank and tested the fit.
The bit holder just fit into my two Yankee screwdrivers without further
modification but was slightly too large for my Millers Falls #61A. I
chucked the round bit holder body into my drill pr*ss and reduced the
diameter of the hexagonal shank with some SC paper glued onto a piece of
scrap. I did this until it just fit my #61A and then polished the shank a
bit with some finer grit sandpaper. The fit was still good in my Yankee
drivers.
The entire operation took about 45 minutes. If you decide to try this I
think it best to have a Yankee type bit to compare the dimensions to as
you proceed. Following is some ASCII art showing the critical dimensions.
This should be viewed with a monospaced font such as Courier.
Not to scale
1 7/16"
<------------------------------------------------>
21/32"
<--------------------->
@@@@@@ *Notch Cutout
@@@@@@------------------------- ------------- ---
@@@@@@************************** ************** |
@@@@@@--------------------------- --------------- 5/32" |
@@@@@@******************************************* | | 5/32"
@@@@@@*******************************************<-----> |
@@@@@@----------Shank corner---------------------------- ---
@@@@@@**************************************************
@@@@@@--------------------------------------------------
@@@@@@
Base of bit holder
*Note - the notch should be 1/16" deep.
****************************
Tom Price
A Field Guide To Millers Falls Type 1 Planes is featured at The Galoot's
Progress:
http://members.aol.com/tomprice/galootp/galtprog.html
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