Seems I had stuffed up the decimal point in my metric calculations -
was 200mm wider than required (length was stuffed too, but that was OK
- was room up in the roof cavity) so, couldnt get the ******* up
through the access hatch into the roof. So, had to cut it down - heaps
of work...

The Moral - I cant think in Metric, cant visualise in Metric, cant
look at metric measurements and think "nah, no way - too wide/long/
narrow thick etc etc"

How you guys cope - bloody sick of doing this...


Order your parts with inch dimensions, and let the shop convert the
units if they have to or let them assign the experienced guy to make
the part because he understands inches.

When I got a drawing that was in metric, I did several things to make
the part. First I would convert each metric dimension to inches,
(Often I found that the part was designed in inches originally given
the way the conversions came out.) and then if I was the one that
would be making the mold, I would then calculate the shrink for the
plastic so I knew how much bigger to make the mold. I would draw a
pencil line through the metric dimension, yellow highlight the inch
(part) dimensions and blue highlight the mold dimensions.

For the times when we had a aluminum casting made, the pattern maker
would have to additionally calculate the shrink rate of the aluminum
and the plastic so the final casting would come out correctly.
(Note: this was at a plastic vacuum forming shop.)

Roger Shoaf