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#21 42rocker

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Posted 09 February 2014 - 08:26 PM

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

Later 42rocker

#22 gbull

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Posted 09 February 2014 - 09:13 PM

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

#23 Cutter

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Posted 09 February 2014 - 10:48 PM

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

#24 nitewatchman

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Posted 10 February 2014 - 02:56 AM

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.

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#25 nitewatchman

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Posted 10 February 2014 - 03:02 AM

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


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.

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#26 Cutter

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Posted 10 February 2014 - 04:18 PM

nitewatchman,

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

#27 Cutter

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Posted 10 February 2014 - 04:22 PM

Who can name this ??

#28 nitewatchman

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Posted 10 February 2014 - 05:19 PM

Adjustable Point Hermaphrodite Caliper.

#29 Sparky_NY

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Posted 10 February 2014 - 05:24 PM

Adjustable Point Hermaphrodite Caliper.


I believe penicillin would help with that

#30 nitewatchman

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Posted 10 February 2014 - 05:29 PM

nitewatchman,

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


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.

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#31 Cutter

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Posted 10 February 2014 - 08:42 PM

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

#32 nitewatchman

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Posted 10 February 2014 - 09:12 PM

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.

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#33 Cutter

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Posted 14 February 2014 - 08:38 PM

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

#34 Roller

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Posted 15 February 2014 - 12:24 AM

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

Frank

#35 Cutter

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Posted 16 February 2014 - 08:33 PM

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

Here's another one to ponder

#36 Roller

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Posted 17 February 2014 - 12:06 AM

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

Frank

#37 gbull

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Posted 17 February 2014 - 12:46 AM

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

#38 Cutter

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Posted 17 February 2014 - 05:02 PM

I probably haven't used it for 20 plus years

#39 Cutter

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Posted 19 February 2014 - 05:12 PM

Handed down from an uncle

#40 Cutter

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Posted 25 February 2014 - 04:03 PM

Maybe interesting to a history buff.




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