Subject: Making holes in spring steel

From: [email-masked] (f.w.kerfoot..iii)
Date: Fri, 13 May 1994 17:19:38 GMT

I am getting ready to make leaf springs for the tender of my 1 1/2"
per foot live steam locomotive. The prototype used leaf springs,
where the anchors at the ends were formed by oblong holes in the
leaves, with the link passing through these holes and a cross-wise
pin inserted through a hole in the link. I want to make the appearance
of the model as close as possible to that of the prototype.

I have found a source of suitable spring material (Power Model supply),
which is hardened, tempered and blued spring steel, 1/2" by .032"
and 1/2" by .050" (I am using two different thicknesses to allow
myself some flexibility in overall stiffness after everything is
built by substituting thicker or thinner leaves in selected places).
This material is roughly Rockwell C48-51 in hardness. I am looking for
insights on making the holes. I have looked for references in Live
Steam magazine, and the only ideas I found were from Don Young, who
suggested center punching over a lead block to create a dimple, filing
off the dimple to make a hole, and then enlarging with successive
drills. Does anyone know of other suitable techniques? The holes
need to be roughly 1/8" wide by perhaps 1/4" long. Two adjacent 1/8"
round holes would probably allow me to get the rest of the way with
files or a small hand grinder. I was considering building a simple
punch, and squeezing it in my vise, or with my small (12 ton) press.
Is a punch a plausible alternative here? How clean will the holes end
up (i.e. how much would I have to allow for cleanup)? I was considering
using something like broken taps, with the unthreaded shank ground
off flat, as a punch. I would still need to build a suitably hardened
die, and a fixture to keep them alligned. Any guesses as to how
such a punch might hold up (number of holes punched per regrinding
of the punch and die)?

Has anyone had success with the Don Young method, or a punch and die,
or anything else, for a job of this sort?

Frank Kerfoot
[email-masked]

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From: [email-masked] (James Kirkpatrick)
Date: 14 May 94 15:05:24 MDT

Sounds like this would be a good job for EDM (Electric Discharge
Machining).  There have been a few articles over the years in Home
Shop Machinist, and I understand there is a series that just finished
in Strictly IC magazine.  Can provide more specific references (or
even copies of some of the articles) if this sounds applicable; a
bit of experience in making electrical projects would be recommended.

Jim

(I suppose I need to add a section on EDM to the FAQ!)