Precision Guage Material

[nornrich]

All,

We are looking to build an extremely precise gauge for setup of in house equipment in one of our manufacturing locations. We are looking to hold +/-0.0001" on the guage. We are looking for a steel that is dimensionally stable to make sure that the guage stays accurate over time. We are going to be keeping the guaging in a temperature controlled room and taking other precautions to make sure that it is stable over a long period of time. One of the things we are looking for some guidance on, is the material to build the guage out of. One of our stamping die manufacturers said that they use a specialized series of low carbon steel to prevent Austentite(?) build up over time. They claim that at the tolerance and dimensions we are looking to hold that a normal tool steel or low carbon stainless is going to show dimensional changes due to surface migration of carbon. Can anyone help point us in the right direction.

Regards,

Rich.....

Richard Nornhold, PE

http://www.personna.com

 

[MikeHalloran]

How big a piece of this Magic Metal will you need?

Seriously, what's the maximum distance over which you need to hold the stated tolerance?



Mike Halloran
Pembroke Pines, FL, USA

 

[arunmrao]

If price is not a concern,you can consider Invar alloy.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[IRstuff]

see:

http://en.wikipedia.org/wiki/Meter#Prototype_metre_bar

90% platinum, 10% iridium measured at the melting point of ice. That was the BIPM official standard for nearly a century.

Beers and Penzes discussed some of the errors associated with the NIST standard meter, which was made from Invar. Note that Invar's CTE is still on the order of 1ppm/K, which means that your temperature control still needs to be less than 2K, to maintain adequate test accuracy ration (TAR).

But, it sounds like you should be looking at some sort of interferometric or laser measurement. 0.1mil is 2.5 um see:

https://www.mysick.com/eCat.aspx?go...Category=Produktfinder&Selections=44263,44211

as an example, but the measurement range maxes out at about 4 inches.

How are you even going to do the comparison without a microscope?

TTFN
faq731-376

 

[SnTMan]

Are you building an instrument (gauge) or a fixture (gage)?

 

[nornrich]

MikeHalloran,

The Steel Mounting Plate for the gauge is 6"x24"x0.5".

IRStuff,

It doesn't make that much of a difference, but I just calculated out the 0.0001" is 3.9 nm. Not much of a difference

SnTMan,

This is a fixture gauge for setting up our process equipment.

And as with all things in life these days, cost does matter.

Regards,

Rich...

Richard Nornhold, PE

http://www.personna.com

 

[IRstuff]

I think you should review your math. 1 inch is 25.4 mm, so 1 mil is 25.4 um, so 0.1 mil is 2.54 um. What is the critical dimension of the gage itself? And how are you going to check the dimensions if you have to take it out of its controlled environment to do the equipment setup?

TTFN
faq731-376

 

[EdStainless]

Either Invar or ceramic (usually Alumina) will be the most stable gage materials.
Our ball bars that we use for CMM cal are Invar bars with carbide balls.
Our gage blocks are ceramic.

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