I found this article about a home made punch for spring steel.
Looks pretty straightforward and effective.
Device For Punching Holes In Saw Blades, Clock Springs, Etc

Description


This section is from the book "Handy Man's Workshop And Laboratory", by A. Russell Bond. Also available from Amazon: Handy Man's Workshop And Laboratory.


Device For Punching Holes In Saw Blades, Clock Springs, Etc


The device shown in side and end elevation at A and B respectively, is made from any old piece of iron or steel, the latter being preferable, as it can be tempered after it is made. The writer is at present using one made of a piece of 5/8-inch square iron some 3 inches long, which has a hole (the same size as the hole to be punched) drilled through it near one end. After drilling the hole cut down with a hack saw as far past the hole as will clear the material to be punched, care being taken that the hole is at right angles to the saw kerf. For a punch use the broken shank of a twist drill of the same size as the hole. This makes a very efficient punch, and the face of the punch is improved by carefully grinding it on a small 3 1/2-inch diameter emery wheel in the manner shown at C; as by this means the face of the punch is slightly hollowed, and its shearing effect is increased.




Fig. 117 - Method of punching holes in saw blades, etc..
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The application of the device in punching a hack-saw blade is illustrated at D. This simple apparatus if properly made will do excellent work on saw blades and springs. The writer has in this way punched a 5/32-inch hole through the blade of a Disston rip saw without distorting the blade or raising a burr around the edges of hole. One can easily make several of these in different sizes, but for hack-saw blades 5/32 inch is a suitable size. It is of course imperative that the punch be a good fit in the hole. The application of a somewhat heavy hand hammer is effective.