[RndTbl] Dimensional hard drives?

Robert Dyck rbdyck2 at shaw.ca
Mon Jan 21 15:53:14 CST 2013

--- Adam Thompson wrote:
> I can't find any derivation 
> for why we call a 2.75" drive a 2.5" drive, since there's no 
> such thing as a 2.5" floppy[1]!  Perhaps the internal platter 
> is 2.5" wide?

Yup. At least they were, manufacturers started shrinking them.

As for lumber: a 2x4 used to be 2" by 4". But that was a rough sawn
surface. Today rough cut lumber is 2"x4". Finished lumber used to have
1/8" planed off each face to make it smooth. That made it 1.75"x3.75".
Then someone got cheap and decided to sell 1.5"x3.5" lumber, and call it

Same with wire gauge. Originally 16 gauge wire was 1/16" diameter. That
is 0.0625", but now what is sold as 16 gauge is 0.0508", so 1/19.7". The
standard states 16 gauge is "19.7 turns of wire per inch (no

Everything is a rip-off, but what are you going to do when it's built
into the standards? As long as they're consistent...

Rob Dyck

More information about the Roundtable mailing list