Engineering dimensions

The vast majority of UK steam locomotive components are made to imperial dimensions. Arguably the most noteworthy exception being the cone size of injectors; those usually being quoted in milimeters.

A third set of dimensions is frequently used by experience practictioners and is recorded for general reference below: -

The Gnats System of Measurement

This system has been in use for many,many years for moving and positioning large objects such as Stonehenge and the Pyramids to the latest CNC machine Tools. Lately it has fallen into disuse as no direct metric equivalent to a "smidgen" has been found.

1 Gnats Whisker = 0.000" to 0.005" or less (i.e. a light gap).
2 Gnats Whiskers = 1 Gnats Doodah.
3 Gnats Doodahs = A Gnats.
4 Gnats = a Smidgen.
3 Smidgens = a Little Bit.
2 Little Bits = a Bit.
3 Bits = a Tad.
2 Tads = a Move It (left or right).
5 Move Its = That's the Wrong Way.
Too many Wrong Ways = Collect 'P45'.

Found elsewhere on this interweb thingy and too good not to pass on.

 

And for fine P.W. adjustment, you have the Gnats Knacker, which when used by P.W. crews represents roughly a lateral shift of 1/2" over a 60' length of rail or a lenghtways shift of 1/4" over the same distance.

Tim

 

Does that mean that a gnats chuff relates to valve timing?

 

Are those Imperial or metric gnats?