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Measuring Strips - A Look at different Tools

by John Bokstrom

Calipers and micrometers are the most widely used tools for measuring strips, but are they the best? Here, in a presentation for the Corbett 2000 meeting, is look at calipers, micrometers and other tools for the purpose of helping the rod maker achieve more accurate strips and thus better rods.

The Waara V-Block
The Waara V-Block

For convenience in handling, three inch pieces of bamboo strip, ten from a typical tip and ten from a typical butt, were used. On one planed flat of each was placed a mark and all measurements were from that mark to the opposite apex. Each strip was measured three times with each tool and the best suited tools were considered to be those giving the most consistent or least variation in results. Tools tested were a Waara V-block fitted to an electronic digital caliper, a Mitutoyo 7312 thickness gage with a 60° anvil, a dial caliper, a micrometer, and a dial thickness gage fitted with a simple custom base, usually used with a series of rods to set planing forms.

The Waara V-block gave the following:

 

Strip First Second Third Average Range
1 .0485 .0485 .0485 .0485 0
2 ..0545
.054 .054 .054 .0005
3 .0595 .0595 .0595 .0595 0
4 .0645 .065 .065 .065 .0005
5 .0695 .0695 .0695 .0695 0
6 .0745 .0745 .0745 .0745 0
7 .077 .0775 .0775 .0775 .0005
8 .081 .081 .0815 .081 .0005
9 .0855 .086 .086 .086 .0005
10 .090 .090 .090 .090 0
11 .089 .0895 .0895 .0895 .0005
12 .090 .0905 .090 .090 .0005
13 .091 .091 .0915 .091 .0005
14 .095 .095 .095 .095 0
15 .099 .100 .100 .100 .001
16 .1035 .1035 .104 .1035 .0005
17 .1075 .107 .1075 .1075 .0005
18 .111 .111 .1115 .111 .0005
19 .119 .119 .119 .119 0
20 .1285 .129 .129 .129 .0005

Note the consistent results. The average variation was only .00035" and in only one case did it reach .001".

The Mitutoyo thickness gage with 60° anvil gave very similar results. The average variation with it was .000275" and only two strips varied by .001".

The Waara V-block and the Mitutoyo thickness gage with 60° anvil are easily calibrated using the fact that when a rod is laid in a 60° groove, the distance between the top of the rod and the apex of the groove is 1.5 x the rod's diameter. For example: using a rod of known diameter in the groove, set the caliper or dial to give a reading of 1.5 x that diameter. From then on strip readings will be direct.

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printed on  20.01.2022

Copyright by ©Frank Neunemann, 1996 - 2022