Christopher Tidy wrote:
Tom Gardner wrote:
How did I ever live without this? In my little world, I have had to
mark and drill holes for bolts, threads and pins and have gotten
lucky and not so lucky. The mark of a good machinist is how well he
RECOVERS from little inaccuracies. My designs have always included
fudge-factors for eyeballed holes, as setting-up edgefinders and
using the BP for drilling every hole is just too time consuming and
relies on accurate edges, good math and back-lash problems. My
thanks to the person that came up with the optical center punch, it
sure fills a spectrum of jobs. I think this should be one of the
first tools in a machinist's box!

If the base is accidentally moved between lining up the mark and
exchanging the optic rod for the centre punch, presumably you don't
find out until you've punched the wrong place? I guess people don't find
this a problem...

Chris

Oh, it's a problem all right.
My technique is to give the punch the lightest of taps. If all worked well
(one gets better with practice) it is easy to drag the point of the punch
into the mark and hit it again to obtain the appropriate dimple.
If I did miss - try again.

Ken.