Surface gage / meter - what works?
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  1. #1
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    Default Surface gage / meter - what works?

    Most engines use head gaskets for which the gasket makers specify a surface finish of 50Ra or better. Some gaskets are OK for 80Ra or better. This is for both cast iron and aluminum surfaces.

    So....in looking at Ebay I see two basic types of meter / gages....the sort that looks like a dial indicator and the type that costs more and is more of a 'black box'.

    Does the black box type work better or is it just fancier? Do either of these accurately measure finishes in the 50Ra range? I looked at the specs and it wasn't readily apparent to me.

    Thanks!s-l1600-profile.jpgdefelsko-positector-spg3-e-3-advanced-body-surface-profile-gage-810257032392-ebay.jpg

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    I've never seen any like that, but have used one of these -

    Test, Measurement & Inspection | Hardness Testers, Durometers & Surface Testing | Mahr Federal 2191800 Pocket Surf IV Portable Surface Roughness Gage EGH-1019 10 MicronM Radius | B580945 - GLOBALindustrial.com

    I can't see a handheld gage being accurate, but if 50Ra is the best you'll need, maybe?

    Also might want to try this, unless you need to get an actual number.

    https://www.mscdirect.com/browse/tnp...BoC8JMQAvD_BwE

    edit: that ^ one is for planing and shaping cutting methods, but they make them that have samples of side milling, face milling, turning, etc.

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    Those gauges are inappropriate. They take single readings of the height above or below an average. What you need is a surface profilometer, AKA surface roughness gauge. Those drag the equivalent of a phonograph needle (if you remember what those are) a fixed distance across the item to be measured and from the up/down motion of that needle calculate either the peak-valley height or rms roughness, as selected by the operator.

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    Thanks to both of you....I'll look for a profilometer.


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