On Feb 26, 6:01*pm, Joseph Gwinn wrote:
In article ,
*JR North wrote:

10/32 hex bolts should not be torqued so tight that even a soft steel
hex wrench should twist. Many times, when a hex fastener is installed
with a powered tool, excessive torque is applied. Hex fasteners need
to be 'cracked' loose with a shock load on the hex driver. Applying
hand twisting torque is almost guarenteed to strip the hex or twist
the hex wrench.

The hex socket screw seems OK, and has been done and undone many times so far.
If I wear the 10-32 screws out, I'll just replace them.

The Craftsman hex key is standing up nicely too. *

The weak link is the old hex key. *I wonder if the plating had something to do
with it, as they may have had to heat the keys to allow hydrogen from plating to
diffuse away, to avoid hydrogen embrittlement. *The Craftsman hex keys are black
oxide finished, as are the hex socket screws.

http://en.wikipedia.org/wiki/Hydrogen_embrittlement

Joe Gwinn



JR
Dweller in the cellar.
On Fri, 26 Feb 2010 18:33:10 -0500, Joseph Gwinn
wrote:

I'm in the process of mounting a DRO on the quill of my Millrite MVI, which
involves replacing the connector block that goes between the quill and the
bronze nut that's moved when the quill feedscrew is turned. *To the new
connector block is attached a 0.125" thick mild steel blade that replaces
the
indicator and to which the sensor of the DRO will attach.

The connector is attached to the blade with two 10-32 hex socket flat head *
machine screws. *There is some scraping and hand filing involved in getting
the
blade to be parallel to a machined reference surface. *The blade moves up
and
down parallel to this surface.

So, there is lots of assembling and disassembling of connector from blade,
and
the 10-32 screws are very tight, and let go with a crack. *So far so good. *
The
first time I tried to undo the screws after really tightening, one screw
came
out without difficulty, but the other one didn't, and didn't feel right. *I
figured that the hex socket was rounding out because the steel wasn't quite
up
to it. *But the socket looked OK. *Pressed on. *The 3/32" hex wrench (key)
turned 60 degrees and felt soft, but the screw finally let go with the usual
crack.

The hex key had twisted axially into a nice spiral, like a piece of
decorative
wrought iron square bar.

Now, I got this US-made hex key set in the late 1950s or early 1960s from a
local hardware store. *I'm not completely sure, as things may have gotten
mixed
up over the years, but from appearance (these were zinc plated) I think they
were made by Indestro Mfg Co. *Never had one of these keys twits before.

The hex socket machine screws are made in India, recently purchased from
MSC.

My 1970s Sears Craftsman hex key set has no such problem.

And the Indians are learning how to make steel.

Joe Gwinn

The Unbrako line was SUPPOSED to do that rather than shearing off or
rounding off, had a demo of that by the counter critter when I got my
set in the late 60s. I've taken out some pretty tight capscrews with
them, but have never had one so torqued up that it pretzeled the
wrench. The alternative is to wedge the hard wrench into the socket,
shear it off flush and have a nice time trying to either remove the
stub or drill out the remains. You might want to look up the torque
limits for that size capscrew.

Stan