Brown & Sharpe 746 vest pocket speed indicator

Sep 17, 2004 2 Replies
W

I discovered one of these cute little instruments at a hamfest, and I remember that these were discussed here in RCM before, but I can't find any posts with google groups search. I've included a proper subject line so that it can be searched.



This tool is in an original box (and 2 contact tips), but doesn't contain the instructions. What an odd looking speed indicator.. the input shaft is a worm that directly turns/drives the numbered dial. There is a spring-disk on one side with a detent bip that contacts a high spot on the dial at only one place. This would effectively produce a click for each rotation.



I confess that I really don't know how this tool indicates speed.. and I'm looking for an explanation from someone wiser than myself



Thanks WB


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N

Speed indicator is really a misnomer, revolution counter would be a better description. It won't indicate speed without a clock and some math. I've never seen the detent on the B&S, the Starretts have a bump on the dial that allows you to count whole revs of the dial as it passes under your finger.

Ned Simmons

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W

I found a description of how it's used on an antique tool sales website.

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Ned's reply makes sense, that would've probably occurred to me at some time before my brain started turning to mush.

The input shaft is held on the center of rotating part (in a straight axis line) for one minute. Each click represents 100 turns, and the number in the dial window is added to the number of clicks.

WB ..................

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