Sunday, March 10, 2013

Aids to Layout and Centre Punching

My near vision is not what it used to be. I'm in no hurry to get reading glasses, though, because I can still read ok, and because getting reading glasses involves business and commerce, and I loathe business and commerce. However, moderately precise work with centre punches and the like can be a bit challenging. Here are a few things I've found helpful.

Masking Tape

Masking tape is a great layout medium for metalworking, and even woodworking at times. Here's an example of its use for spotting a hole location on a small piece of steel flat.

Note the two centre punches. The smaller one I keep finely pointed and sharp. The larger one is relatively a bit blunt.

Illuminated Magnifier and Black Marker

What I do with the black marker is I blacken the tip of the fine centre punch. That has a remarkably good effect on my ability to see the tip of the punch clearly. Here's how I proceed:

a) Hammer ready next to the back of the vise.

b) Viewing through the magnifier, I get the point of the punch positioned at the intersection of the lines, and press the point lightly down on the tape. That gives me a non-skid dimple in the tape that will retain the punch point's position, while I carefully move the work and the punch together to the back of the vise.

c) My left hand takes over holding the punch. I pick up the hammer with my right hand and strike the punch. Here's the outcome.

Maybe not perfect to within 0.0005", but not bad at all -- probably far better than I would have done without the aid of the tape and the blackened punch point.

I follow up with the bigger, blunter centre punch, and I've got a punch mark that will get a pilot hole started truly.

The fine centre punch's tip must be re-blackened for each use. On large work, have the work well lit, and use a hand-held magnifier to achieve the same effect.

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