Measuring beyond the decimal place for distances >600mm

[lamanoditrento]

I have bought a 610mm engineer's straight edge that I thought was guaranteed to be accurate to +/- 0.025mm. But that turns out to be for its straightness, not its length.

So now I am wondering the best way to measure my straight edge to an accuracy for setting up a full nut/saddle compensated setup?

[Trevor Gore]

I use a piece of 1/8" by 1/2" brass rod (Bunnings) that I machined to length on a milling machine with a good digital readout. It turned out to be 0.2mm short, but I just zero my calipers at +.2 to take care of that.

If I was doing it without heavy machinery, I would likely just make a number of scratches approx. 150mm apart on the material, deep enough to locate the tips of my 150mm calipers. (The Mitutoyo ones that I've used for years open to 153mm). Step out until the distances sum to exactly 600mm and file to that using a shooting board to keep the end square.

There are likely better ways...

[Andos]

Here is a 650mm Vernier caliper https://m.ebay.com/itm/STARRETT-NO-123M ... 2731788098.

The other way is to take the straight edge to a machine shop and give them the length and tolerance to machine it down to.

[Trevor Gore]

Of course, there are always real measuring rods....

https://www.higherprecision.com/product ... -243MA-600

[lamanoditrento]

Great thanks, Trevor

[kiwigeo]

If you can't afford a micrometer these are far cheaper

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