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OD measurement in a compact space

OD measurement in a compact space

I have a need to inspect shafts for wear in the field. The most accessible I can provide is such that the important journal (say 2.5 dia) is still surrounded by a housing with 8.25 ID. Need +/-.0005" on diameter accuracy or better.

This obstructs the use of any common measuring tool. A 2-3" OD mic have the anvil assembly which takes up too much space to fit within 8.25 ID.

Have tried longer jaw calipers however the longer the jaw the less accurate the result.

Looking for ideas. Best idea I have so far is a custom c-style snap gauge. Would strongly prefer something off the shelf and also not require a plug gauge to set it up.

Next option is a ring gauge with feeler gauges or maybe custom cut to fit a plunger indicator.

I suspect someone out there has a simple and compact way to do this, we're just not thinking of it yet.

Thanks, David

RE: OD measurement in a compact space

Plastigage, if you are inspecting for clearance between journal and bearing. If you must have an actual measurement it's hard to say without seeing the space confinement that you're working within.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: OD measurement in a compact space

Ah I see, yes Plastigage might help. However I've only seen plastigage used for split bearings. My fitted component is one-piece and slides over this section of shaft. Never tried to plastigage that arrangement before.

RE: OD measurement in a compact space

I understand. Yes, that would be difficult. Your idea of a snap gage might be the next best thing. Good luck.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: OD measurement in a compact space

Maybe a custom split gauge of a known diameter you can clamp over the shaft, then use that with Plastigage.

You are judged not by what you know, but by what you can do.

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