The message
from "Mark" contains these words:

And just for you Mark if 1&6/8 was down on the work sheet then who am
I to go to the powers that be and say...this should be 1&3/4"

Sorry I was being pedantic
When I was at school you would never _ever_ dare write 1-6/8
1.750 perhaps.. :-)

It probably has no application in this instance but I have a (very)
vague memory of a convention for unstated limits in which the nature of
the units gave some guidance to the tolerances required in which case I
would expect dimensioning in eighths would demand a closer tolerance
than dimensioning in quarters.

--
Roger Chapman