Accurate Measuring Tools

[biggsgolf]

I have been using digital calipers to measure objects and find that they are not accurate. An example is when I measure the inside radius of an existing cylinder endcap where the O Ring fits. I thought about trying a micrometer but think the tips might be too wide to fit into the O Ring channel? I need to replicate a 70 mm cylinder forward endcap. Ideas?

[Peter W]

You could always use rods in the groove like the 3 wire method for measuring screw threads ? If the 0-ring groove is 3mm /⅛" then use that sized rods to give the micrometer somewhere to measure from ?

Or slip gauges or parallels. Anything that will fit into the groove with a known dimension that can be subtracted ?

Peter

[RCENGR]

An outside caliper will get in the groove for an accurate measurement. https://www.amazon.com/Big-Horn-1905...015YHDUU&psc=1

[He Who Shall Not Be Named]

I have been using digital calipers to measure objects and find that they are not accurate. An example is when I measure the inside radius of an existing cylinder endcap where the O Ring fits. I thought about trying a micrometer but think the tips might be too wide to fit into the O Ring channel? I need to replicate a 70 mm cylinder forward endcap. Ideas?

Grind the face of the tips to fit. Duh! Tools are to be used, not worshiped.

[Subculture]

Some of the cheaper digital callipers can skip readings. Some more expensive ones have an absolute reading so they can’t do that, or you can go old school and use an analogue set, which don’t need batteries and will provide a reliable reading every time.

A micrometer is always considered to be the benchmark for most accurate measurement, but really vernier callipers are more than adequate for the tolerances we are likely to be using.

[CC Clarke]

Cheap digital calipers give free erroneous readings.

Mitutoyo offers a set digital caliper and micrometers housed in a wooden box with uncompromising accuracy. I've used mine for years and never had a tolerance issue. These are commonly used in the aerospace industry for a reason. Worth every penny!

These are supplemented with a full set of pin gages from Meyer - another trusted brand.