DoN. Nichols wrote:

snip

Allen keys are a useful source, and one I hadn't thought of. Thanks for
that idea. But a box of 100 is about the same price as that thin bit set
from Brownells.


With the possibility of making several hundred (at least 200)
from the hex keys. Compare that to the number of bits in the Brownells
set.

True enough. But to be honest, I suspect that I wouldn't need to make
more than 20 bits (in a reasonable length of time, anyway). So the
majority of those Allen keys will sit on a shelf unused.

Due to the unknown amount of time and experimentation it
will take me to make a good screwdriver bit, I am drawn towards the
Brownells set.


O.K. You still should *try* making a screwdriver of your own,
to see just how difficult is is (or isn't).

I will. I actually feel a bit bad not making the screwdrivers, but
there's always a point at which you have to decide what you're going to
make and what you're going to buy. Right now I have too many projects on
the go, and making screwdrivers seems less appealing than the other
projects I'm working on. But when I find a worn screwdriver that I no
longer want, I'll have a go at grinding it and see how neat it turns out.

I think in this case you're right. I do have a preference for fixed
blade screwdrivers when they're available, though. Interchangeable bits
aren't always held tightly in the handle, and the handle is usually a
bit bulkier.


But -- the interchangeable bits allow me to use them in a
electric screwdriver with adjustable torque limit. For some things, a
manual screwdriver is about as good, but when dealing with (for example)
changing out a set of cards in an old Sun 4/370 computer (3U VME bus),
you have two Allen head screws, M3x0.45 with about 1" of thread to back
out for each card -- and about 12 cards total in the system.
out for each card -- and about 12 cards total in the system. And you


[ ... ]


The electric screwdriver which I use was originally made by AEG,
and more recently Panasonic and Milwaukee -- same screwdriver, different
color plastic. :-)

I have a thing against electric screwdrivers. While they may be faster
and have an adjustable torque limit on some models, I find they give
poor control with slotted screws.


Put a sleeve over the head -- just large enough to cover the
diameter of the screw head. You can even get straight bits with a
spring-loaded collar for the purpose. The screwdriver which I made for
English system concertina endbox screws includes such a sleeve to keep
me from slipping and gouging the wood of the endbox. And I never use an
electric screwdriver with those, as the threads are fast enough and the
thread engagement is slow enough to be no problem.

Doesn't the sleeve prevent you from seeing if the bit is located in the
slot?

As it turns out, I don't often use slotted screws. When I am
building something from scratch, I tend to choose Allen head cap screws
and button head screws with Allen sockets for most things, with security
Torx used for a few things. And I often work on things fitted with a
lot of Phillips screws, but seldom slotted ones these days. And for
wood screws, I prefer the Robertson (square drive) screws.

Personally I think that sometimes a slotted screw head is needed for
appearance. On some devices, a Phillips or Allen head looks wrong.

I've never seen square drive wood screws. Must be an American thing.

I just prefer to use a normal
screwdriver and estimate the required torque. I have only once damaged a
thread in this way, and that was a long time ago, so I don't think I'm
doing too badly.


I just used it this evening for swapping subassemblies between
two Exabyte Mammoth (8900) computer tape drives. Almost everything in
there uses screws of 2mm diameter (1.96mm from measuring a typical one)
and the lowest torque setting (1) on this driver releases at the right
point to avoid overdriving these into the relatively soft metal of the
chassis. The more serious problem was finding the right size (T6) of
Torx bit -- but they can be found in 1/4" hex shank size.

There are two intermediate clicks between (1) and (2) on the
electric screwdriver (and it goes up to (6)). I use the (2) setting
commonly on both the 6-32 screws and the fairly common 3mm ones used for
mounting tape and CD drives in computers.

I also have a set of two manual torque limiting screwdrivers by
Utica. 6-30 Lb-In, and 0-100 Oz-In. Both of these also accept 1/4" hex
shank bits (as well as adaptors to a 1/4" square drive for sockets.)
The most frequent use for these (aside from the spare of one which I
keep with my best English system concertina) is in removing and
replacing CPU modules in Sun Blade 1000/2000 systems and Sun Fire 280R
(same system board and CPU modules). Sun considers the torque important
enough here so they supply torque measuring screwdrivers with the
systems -- the one with the Sun Blade 2000 and the Sun Fire 280R is
better than the rather simple design in the Sun Blade 1000. (According
to the manuals, later systems were shipped without *any* torque driver,
but the torque drivers were supplied when you bought replacement or
upgrade CPUs. They also clearly spell out the needed torque (5 Lb-In)
for those who have a general purpose torque screwdriver such as mine.
The jackscrews take a Robertson (square) bit, and are marked with a
fluorescent green ring around the screw holes -- matching the color of
the torque screwdriver body, or the plastic carrier holding the earlier
design (a ring which closes at the proper torque) which slides between
the two disk drives in the system.

Sometime I might get a manual torque limiting screwdriver, but for the
time being I'm managing without.

Your narrow slotted screws are not really properly designed.
They were made with the size of slotting saw which the maker had on
hand -- and he did not want to buy a bunch of other thicknesses.

I think that some, though not all, screws with narrow slots have larger
heads than standard screws today. The traditional large "cheese" head is
becoming very uncommon.

It is also possible that in some cases narrow slots were intended to
signify that a high torque was not required (there are, of course, other
reasons for using a large diameter screw). But this is just my speculation.


Yes. Possible.

When were these made? And where? IIRC they are in clocks, but
from back in the period when most hardware was custom made by the
clockmaker, or from when production lines and supplies were more common?

Mostly on electrical equipment made between the 1930s and 1950s,
together with a few on clocks. You could certainly buy those big "cheese
head" screws in England up until recently. I bought some 0 BA screws in
that style a few years back, but when I went back for more, they were no
longer available.

Yes, they have a larger hexagonal section below the handle for this
purpose in addition to the hexagonal shaft. Also, the shaft goes right
the way through the plastic handle and emerges as a metal cap.


Hmm ... that latter feature is a design to survive abuse by
hammering on the end of the driver.

Indeed. Not something I generally do to them, though.


I did qualify that treatment as abuse, after all.


It probably also
makes the handle plastic less likely to fail under torque at the
junction with the metal. But the Wera plastic is much less brittle than
that used on cheap screwdrivers, so there's an advantage to start with.


I've never had even a cheap screwdriver handle break on me.
Granted, I don't pound on the ends with a hammer. :-)

The ones I've had break were made from a clear yellow plastic. When the
plastic broke, it looked almost like glass. I didn't hammer them. It was
torque in normal use which caused them to break.

Best wishes,

Chris