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Old September 21st 06, 08:40 PM posted to rec.aviation.homebuilt
Ernest Christley
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Posts: 199
Default Marking sheetmetal

RST Engineering wrote:
You are kidding, of course? You are marking a line 40 mils wide and
expecting a piece to come out to 20 mils or better accuracy?

Jim



"DonMorrisey" wrote in message
ups.com...
At the risk of beating this subject to death, use a sharpie, however a
Fine Point Sharpie is too thick. An Ultra-Fine Point Sharpie makes a
line approx 1 MM in width.

Don...




And if you could put the bend within 10 mils of where you intended every
time, would anyone care?

If the designer calls for that amount of accuracy in anything other than
bearings, it's time to find a new designer. I was told by a old-time
sheet metal worker that unless the plans state otherwise, standard
accuracy requirements are 1/32". That's plus or minus .03125 in either
direction for a .0625" window.

On parts that I do want to cut straight because I want them to be
pretty, I mark with a sharpie against a metal ruler, then aim for the
side of the line. The metal ruler limits where the sponge on the tip of
the marker can go.