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Hahn & Kolb micrometer

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meninspex

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Can anybody tell me how to read this micrometer?


It's made by Hahn & Kolb and has Nr.1731 stamped on it plus Messbereich. 10-20 (measuring range). My main problem is with the spring loaded plunger, with the graduations marked on it, which doesn't seem to connect to the moving spindle.

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IMG_20210723_151116047_HDR[1].jpg
 

HappyHacker

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It looks as if it has been made to measure a specific item and indicate the over or under dimensions. If you measure the diameter of the bar does it measure zero?

The rod sticking up from below would be used to ensure that the reading is always taken at a specific point perhaps to ensure a bar is always measured at the full diameter.
 

meninspex

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Thanks for that but I'm afraid I'm no nearer as moving the spindle, by means of the knurled ring closest to the frame, has no effect on the graduated scale on the plunger at the back end and there is no scale of any sort on any other part of the instrument. This plunger is sprung and goes in to the same depth regardless of where the moving spindle is set. The bar, which I assume is a test piece, is 15mm diam.
 

Stevekane

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Does the “scale” part push in, like giving an injection and give you a reading with the spring loaded button in the anvil end taking up the slack when measuring preset tolerances,,I think the scale reads both under and over measurements?
 

Gerry

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You set the anvils to the width required using a gauge block then the scale is used for a quick tolerance check on the workpiece e.g. +/- 0.1 by pressing the spindle. Think of it as an adjustable snap gauge.
The setting bar is for calibration.

Gerry
 

deema

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There are two screws which release the lower ‘rest’ and also the measuring arm allowing you to move them in and out. As Gerry said, you take a piece you want to copy, or a known test / standard bar / pin and set the gauge my moving the two bits so that the plunger measures zero with the test piece being measured. You now have a snap gauge, or standard that you can then use to quickly measure a batch of parts. Often used by inspection departments or on the shop floor for a machine producing lots of the same component.
 
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meninspex

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Thanks again for your input folks, the setting tool is in fact a hollow bar measuring 15.00mm diam. This instrument was part of a consignment of tools that I inherited from my late cousin who was a keen model engineer and an inveterate collector of tools , new and old. The word magpie comes to mind. I can't think that I would have any use for it so will probably Freecycle it along with other unwanted items.
 

Inspector

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I would put it on eBay. If properly described it will go to someone that can use it even if for a low price. Just make sure it is in working order. You'll be surprised what a specialized tool like that can go for if there are a few people interested in it.

Pete
 

TheTiddles

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As others have said, that’s not a micrometer.
Although they’re expensive new, second hand unless someone knows it’s still got the accuracy and precision it had new, it’s not worth a lot.
Micrometers are a good example, a £200 micrometer is worth 10p if it’s been dropped and people can’t tell remotely. Still it doesn’t stop some people, who then advertise them again days later once they’ve found out.
 
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