Optical Center Punch Self Holding Punch

[mklotz]

I don't do much accurate center-punching anymore; coordinate drilling is easier and more accurate. But, when I was starting out, I did enough of it to learn a few things that I'd like to pass along here. These are just observations that others may find useful. PLEASE DO NOT CONSTRUE ANYTHING I WRITE HERE AS CRITICISM OF JR'S DESIGN. With that said (and hopefully taken to heart by all), let me proceed.

Looking at the location of the punch tip from an angle never worked well for me. I decided that a more vertical, magnified view of the location would make things easier to see. To that end, I attached the magnifier close to the punch axis and above the punch tip.

This worked a bit better but was a bit tricky to hold; I knew there must be something better.

I realized that magnification wasn't really necessary in most cases. Almost all the prick punching was done at the intersection of layout lines. If we could locate the punch using the lines themselves rather than trying to hit their intersection, everything would be easier. So, when I ran across this commercial product...

I knew I had found the holy grail of punch locating. :-) The punch is spring-loaded and resides permanently in the base. [Thus avoiding the major complaint associated with the devices that have magnifiers and punches that must be interchanged in a single hole. A major feature of JR's design is eliminating that undesirable design feature.] Scribed in a recess in the base (see next photo) are two lines. When these lines are aligned to the scribe lines, the punch sits directly over their intersection point. A slight tap with a small hammer marks the point well enough to be found by touch with a center punch.

The recess in the base in which the lines are scribed is important. The base will become scratched from contact with metal but the lines in the recess are immune to that scratching so they will remain very visible.

I no longer remember where I bought this device so I took a photo of its box top; that's all the information I have on it.

Later I realized that, while four lines pointing at the intersection are helpful, you really only need two. This observation makes it simple to machine your own version of the device from more durable metal as I did in the photos below...