On Thu, 08 Aug 2013 13:17:30 -0400, Ed Huntress wrote:
On Thu, 08 Aug 2013 11:53:17 -0500, Tim Wescott
wrote:
On Thu, 08 Aug 2013 11:40:27 -0400, Ed Huntress wrote:
On Thu, 8 Aug 2013 08:12:16 -0700 (PDT), Bob La Londe
wrote:
I am sure you are familiar with them. The flat black (sometimes
otherwise coated) wrenches that come with a lot of power tools for
changing blades, bits, discs, etc. They look like they are stamped
out of sheet. I am certainly not going to make a stamping die for one
wrench, but I am sure I could cut one out of flat stock on the mill
when I need one and a regular mechanics wrench won't fit. The thing
is I don't know what steel to use.
How about an inexpensive alloy that might be easily heat treatable. I
don't think surface hardening would help for a wrench or a spanner as
the cross section would still be softer, but maybe somebody who knows
better could speak up?
Those things are almost always made of plain carbon steel. 1070 is
common for tools and other odds and ends that need strength with a
moderate amount of ductility.
You'd be suprised how *few* things that we think of as high-strength
are actually made from alloy steels. For example, the piston rods on
shock absorbers and struts: Plain carbon, 1070.
Quality wrenches often are made from a proprietary grade of
chrome-vanadium alloy. But the advantage in most practical uses is
slight.
That depends on what you see as "practical use". If it says "chrome
vanadium steel" on the outside, and that makes the wrench sell more
without you getting sued for false advertisement, isn't that a highly
practical use from the "let's make lots of money" point of view?
Man, you're a cynic. g
I don't know what they're using now, but 30 years ago, quality hand-tool
makers -- Williams, Sears, Snap-On, etc., used either an alloy like AISI
6118 (SAE J1268) or a similar proprietary, custom steel grade.
The advantages are that they develop more hardness and strength with
less carbon, and they retain some ductility, or at least resistance to
brittle failure, even with high-strength heat-treatments.
But, again, those advantages are only meaningful in some circumstances.
If you're ham-fisted and you abuse and overstress your hand tools, the
alloys may save you some grief. But really, for most uses, plain-carbon
steel wiill give you plenty of strength and hardness.
My understanding of the whole alloy-steel thing (which may be faulty) is
that the alloys don't really change the ultimate strength to which you
can heat treat in a thin section, but they make it easier (sometimes
vastly so) to attain that strength in a piece where you can't get fast
cooling everywhere.
So things that are fairly constant sections, and get made in massive
enough quantities that you can afford to really fine-tune your heat-treat
process, can get made with plain high-carbon steel.
Forged wrenches, OTOH, have massive sections sitting right by thin
sections, and would benefit from some alloying.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com