[TheForge] Which Drill Rod?

[David E. Smucker]

Bruce,  No matter which steel you use they will all deflect the same amount
for the same load since all steel has effectively the same modulus (30 x 10
to the 6th).  Depending on the strength they may bend and take a permanent
set.  If you have much end loading then the shaft may buckle because they
are very slender.  Deflection will be to the cube of the width for the same
loading no matter what alloy you use.  If one shaft is 4 inches and the
other 12 and they had the same loading (that may not be the case) the then
the 12 inch one will deflect 27 times than the 4 inch.  12 cubed divided by
4 cubed or 1728/64.  The only thing you can do to change this is to increase
the diameter of the longer shaft.  That said I would give the O1 a try.   It
is easy to heat-treat.  Heat to just above critical and quench -- for very
small section like 1/8 just let it air quench -- then temper in your kitchen
oven at 375 to 400 F.

Dave Smucker
Brasstown, NC

-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net] On Behalf Of Bruce .
Sent: Friday, November 29, 2013 9:07 PM
To: Blacksmithing List Sponsored by ABANA
Subject: [TheForge] Which Drill Rod?

I don't work with hard steel much, so I'm turning to this group for advice
as to which alloy to choose for my applications.

For two separate applications I need small OD (preferably 1/8") shafts that
are quite rigid and will deflect little or not at all under the conditions
of use.  In one case, the working length of the shaft will be 4"-6"
(between supports).

The load on the shaft will be distributed across its length -- like as for a
sheaf of pulleys -- and will total probably only a few pounds-force.  In the
other case it will be closer to 12".  In neither case will the rod rotate,
but in one case pulleys will rotate on it.

Naturally I don't expect NO deflection, but simply want to minimize the
deflection by using a hard steel, rather than whatever might be on the
shelf.  I especially don't want the steel to bend and kink, as does common
steel in such applications.  (The voice of experience is talking, here.)

McMaster has O1, A2, D2, W1, and M2 in lengths of 12" or more.  For the
quantity I need, all of these are affordable, though O1, A2 and W1 are
considerably cheaper than the others, so I'd lean toward those, other things
equal.  These come unhardened, so I expect to have to harden it, and the
ease of doing so is an issue.

Any advice or pointers?

Bruce
NJ
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