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International Prototype Metre Bar Replica
August 31, 2014 9:19 PM   Subscribe

I want an International Prototype Metre bar. Actually, I'd settle for half-meter long bar (or maybe something scaled down to a manageable size?) with a Tresca cross-section, but I can't seem to find anything like this online. Any suggestions for where I could find something like this?
posted by Nonsteroidal Anti-Inflammatory Drug to Grab Bag (5 answers total) 2 users marked this as a favorite
 
Is a t-slotted extrusion ok?

What's your application? If you're just looking for a nice object, maybe get a combination square or double square to cherish and fondle.

Or an aluminum or steel straightedge. (A machinist's catalog or mcmaster ought to have metric.)
posted by sebastienbailard at 9:39 PM on August 31


What's your application?

It's part of a gift. This somehow needs to tie back to being the standard, so unfortunately "nice object" on its own won't cut it.
posted by Nonsteroidal Anti-Inflammatory Drug at 9:48 PM on August 31


I suspect bars with a Tresca cross-section may only have ever inhabited metrology labs like NIST, back before they used a wavelength of krypton-86 light or then the modern "1/299 792 458 of a second times c" measure.

Making a bar with that particular profile is a bit tedious and a machinist or metrologist isn't going to do it without a good reason. Instead they'd be working with secondary measures that were traceable to the original meter bar but shaped differently. (I guess, not being a metrologist.)

Maybe a kyrpton lamp bulb or something meaningful from a 'neon' light shop, where they often commonly use krypton, apparently?
posted by sebastienbailard at 10:01 PM on August 31


Probably the cheapest way of getting something with absurd precision would be a gauge block with a traceable calibration certificate. Much smaller, too.
posted by scruss at 11:13 AM on September 1


That Tresca cross section shape is unique, a nice desk ornament might be an International Prototype Centi-metre. Maybe have one of those 3D printing places print one for you. How lax are you with regards to material, would steel suffice? Platinum? And how accurate must it be? Would you want it the same height and width as the original (I can't find the dimensions, but it looks roughly 2 inches by 2 inches (is it sacrilege to refer use inches here?)), or would a miniature suffice? Perhaps jewelry, this place might get you there http://www.mymo.is/
posted by at at 3:01 PM on September 1


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