On 2008-10-18, Christopher Tidy wrote:
DoN. Nichols wrote:
[ ... ]
You don't think there's a chance that the screwdriver will end up in my
chest, if the tip catches on the wheel?
Not too likely. since you should not get the tip at an angle
which makes that likely. And it is more likely to be driven down than
towards your chest, given the presence of the guard at the top.
I had a look at the grinder yesterday. I think it would be possible to
get a screwdriver bit into the right position, and that it probably
wouldn't stick in the wheel. But then I had a look for a screwdriver of
the right size to grind, and could only find my light-up electrical
screwdriver. I didn't want to modify that, so I'll have to wait until
I'm in a tool shop to buy a suitable screwdriver.
I would really not want to modify a good screwdriver -- I would
prefer to start from scratch. A cheap screwdriver I would (and have)
modified -- for example when I needed a split blade to drive a nut which
had a slot on either side of the screw -- but needed a gap in the blade
for the screw to project into. (Hex head on the screw, so the nut
*must* rotate, and the nut fit into a recess in a connector.) So I just
grabbed a cheap screwdriver (Stubby one of the kind provided in Army
toolkits, since I was working for an Army R&D lab at the time, and this
was truly a government project, so I could expend a screwdriver for the
cause. I simply took a file to cut the needed notch.
Perhaps what you need to do is to get a screwdriver with
interchangeable tips (here they have 1/4" hex shanks and a corresponding
socket in the handle), where you can buy a large number of hex
screwdriver bits of many sizes and styles, and simply grind the bit to
fit a particular screw -- mark it, and keep it for the next time you
need that size. Replacement bits are inexpensive, are good tool steel
for the purpose, and it should be easy to make a fixture to hold the
1/4" hex shank while grinding it.
I think perhaps part of my reluctance is because I'm a bit of a
perfectionist. I like good, accurate tools and I'm not sure that I can
make a screwdriver of that standard. Good screwdrivers are really nice
to use. The way they snugly fit screw heads is satisfying.
Good screwdrivers with replaceable bits sounds the way to go,
then.
But a cheap screwdriver which has been reground to fit the screw
in question is better than a perfect screwdriver with is either too
thick or too thin.
The best screwdrivers I have are a set made by Wera. Nick Mueller
recommended them. They make the other screwdrivers I have look awful by
comparison. The just fit the screw heads so precisely.
Yes -- with the caveat that all that I have have the tip width
and exposed blade length specified in metric units, which may mean that they are
not a perfect fit for an old imperial screw. I note that the two in my
belt pouch ("Wiha", not "Wera") don't specify the blade thickness. The
2.5x50 (width & length) measures at 0.59mm (probably target of 0.60mm),
or about 0.021".
Wera and Wiha are different brands. Wera screwdrivers have a distinctive
multicoloured handle with the dimensions of the tip printed on it. I've
been very impressed with them.
That sounds like a description of the Wiha ones in my belt
pouch. Handles are black with a red cap which pivots to allow you to
hold it pressed into the screw slot with a single fingertip. The
width and thickness are printed on the black part of the handle.
The Wera screwdrivers also have a hexagonal shaft. It occurred to me
yesterday that this could be helpful when trying to modify one, as it
would help to ensure that the two ground faces are parallel.
Hmm ... I've seen some screwdrivers (SnapOn among them) which
have a hex forged just below the handle for allowing wrench to assist
with a really tight screw. (And yes, the screwdriver was forged tough
enough to handle that kind of abuse.)
[ ... ]
You have a lathe? You have a knurling tool? Turn a handle from
aluminum or brass, knurl it for a good grip, drill to fit the shank,
drill for a setscrew, and mill (or file) a flat on the shank for the
setscrew to bear upon. Do this *before* you grind the tip, so you have
something to blunt the shank if it does happen to dig in -- though it
shouldn't as long as you are holding the tip tangent to the wheel. And
you really don't want to be pressing hard enough to encourage a dig-in
even at a wrong angle. Keep the pressure light, so you don't overheat
the workpiece.
I've got access to my father's lathe, but not a knurling tool.
Then consider getting a knurling tool for it. Ideally a
scissors style knurling tool, so you don't overstress the machine.
[ ... ]
I think the Brownells set is likely out of the question because of their
ludicrous shipping charges. I am going to call a few horological
suppliers on Monday see if they know of a source. Surely someone must
make suitable screwdrivers?
Changeable tip screwdrivers, with lots of spare tips so you can
grind them to fit different screws.
If I don't have any success, I will have to make one and see how neat it
turns out.
Good Luck,
DoN.
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