Tools

Cutter you could be right. It\'s been several years since I saw the set of rulers.

Later 42rocker

Rocker, as part of my apprenticeship at GE back in the 60\'s I spent a stint in their foundry. Patternmakers use what are known as contraction rulers. They have thermal contraction values built into them. They came in a variety for different thermal contraction rates, 1%, 2% etc. They allow you to build patterns without having to constantly add the contraction rate to each measurement. I\'ve also built a lot of injection molds, and the first thing you would have to do is add the shrink factor to every dim.
Gary

Also used  in the past for model/pattern making
was a Pi-tape.

We used Pi Tapes to turn large diameters on Pressure Vessels - 240\" to 252\" +/-.015\" for example.

You have to very careful that the work piece and the tape are very near the same temperature and as close to 68F as possible.  

nitewatchman

[quote name=\"42rocker\"]Have a friend that has a large set of rulers that are \"off\". Ok, not really \"off\" he was a die maker and the rulers were made special that way to cover for shrinkage of the wood and other materials that he worked with. They look normal till you start to compare them next to each other. He has won a few bets with them.

Later 42rocker[/quote]

Shrink Rules - used primarily in foundry pattern making. Patterns must be enlarged to provide a cavity that is larger than the final part to compensate for the shrinkage of the part as the metal cools. Some of our large manganese steel patterns are a couple inches longer than the cold part, the hot metal shrinks that much as it cools.

nitewatchman

nitewatchman,

I\'m surprised your still using Pi Tapes.
Laser measuring for large diameters has become so accurate.

Who can name this ??

Adjustable Point Hermaphrodite Caliper.

[quote name=\"nitewatchman\"]Adjustable Point Hermaphrodite Caliper.[/quote]

I believe penicillin would help with that

[quote name=\"Cutter\"]nitewatchman,

I\'m surprised your still using Pi Tapes.
Laser measuring for large diameters has become so accurate.[/quote]

Several years (1970\'s) and a couple life times ago. We built, machined and assembled Commerical and Navy Nuclear Power Plants. Finished BWR6 Reactor with Internals weighted 1148Tons without the vessel head. A very good way to measure a 266\" O-Ring Groove on a VBM.

I am in the Railway Turnout business now. Rarely see a tolerance smaller than the little mark on a pocket tape.

nitewatchman

I thought the answer would come from the 10% discount community.
But, a good laugh with Sparky\'s post.

Just after getting out college, I had an \"Instructor/Mentor\" in Chicago Bridge & Iron\'s Engineering Training Program that would only approve of laying out a shaft center using a \"morfidite caliper\". He was a great machinist but set in his ways.

nitewatchman

Here\'s a small caliper made from brass and wood, some
old timer gave me this about 50 tears ago.
inside - outside , lines are at 1/32

That\'s the same type of caliper I used to build my gun! No digital display !

Frank

Roller,
There\'s not many of us left, pre digital, pre dial calipers.
String and stick

Here\'s another one to ponder

Looks like a trammel to me.  I still have one but it doesn\'t look like that one.

Frank

I.ve got one just like it. Think it\'s a starrett with two bars and a connector to join them. Don\'t use it very often but when you need one you really can\'t beat it.

Gary

I probably haven\'t used it for 20 plus years

Handed down from an uncle

Maybe interesting to a history buff.