On Thu, 11 Nov 2010 18:52:24 -0800,
wrote:
As the punch mark have definite dimensions I tried just locating
crossed lines. This is quite difficult: Just because you can see the
lines on the bench does not mean you will see them clearly under the
spindle, paint etc. notwithstanding. The results, confirmed with
center drilling , were considerably worse than center-finding a punch
mark, however small.
==================
different problem -- from what you describe in the complete
post you are doing better than expected. For ultra precise
work you need to go to a jig borer or grinder $$$$$$$.
Google on SIP and Moore for examples
http://www.weldershop.info/205/moore-jig-borer/
for some discussion see
http://bbs.homeshopmachinist.net/showthread.php?t=1468
for one less expensive solution see
http://www.wttool.com/product-exec/p...m_source=froog
and the one I have and like
http://www.skidmoreengineering.com/i...s/Page1171.htm
Key is to use a very light hammer and just a tap to mark the
metal, and then enlarge with a more robust punch and hammer.
A mighty blast on the punch with the optical center finder
will destroy the tip.
For high precision layout invest in a surface plate, a right
angle plate, and a space block set and use this with a flat
scribe (make from HSS lathe tool)
for example
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
http://www.use-enco.com/CGI/INSRIT?P...&PMPXNO=950511
http://www.use-enco.com/CGI/INPDFF?PMPAGE=461&PMCTLG=00
http://www.use-enco.com/CGI/INSRIT?P...PMAKA=418-4525
Bright light at the machine tool will help.
Also consider
http://www.use-enco.com/CGI/INSRIT?P...MPXNO=25219105
after you are set up to do precision layout. Problem with
smaller machines is quill to table/workpiece distance.
cheaper
http://compare.ebay.com/like/3503879...=263602_304662
http://www.amazon.com/Made-852-6-ran.../dp/B0006J3E4Y
-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).