Monday, June 20, 2011
Odd-ball tools fascinate me and so I couldn't resist this one. It came to me at the weekend while digging through a box of second hand tools for sale. I'd already acquired a spoke-shave, for no better reason than I don't own one already, and was looking at a pile of steel rules when Dave shouted at me "You don't want to use those Phil."
Enquiring why, it was explained that they were pattern makers contraction rulers, sometimes called "shrink rules". These are used when producing anything that will be cast in a material, such as whitemetal, that shrinks when it is moulded. So the markings are slightly bigger than they should be. Each scale is marked by the amount of contraction so on the scale above we have scales for 1/40 and 1/30 contraction.
The only material I use that shrinks is polyester resin, and even that is negligible. Thus, this tool isn't actually of any practical use. Maybe I could make models with it that are slightly bigger than they are supposed to be. Never mind, it's another interesting addition to the toolbox.
Anyone else bought an odd-ball tool that they have never used ?