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Micrometer Having Both, Lateral and Rotary Adjustment

2nd March 1945, Page 35
2nd March 1945
Page 35
Page 35, 2nd March 1945 — Micrometer Having Both, Lateral and Rotary Adjustment
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• A s is well known; plug gauges are t"kused in the production of components which have to be strictly interchangeable. This limit-gauge system is based on the recognition that certain tolerances in dimensions are possible without deviating from the required degree of frt. In the case of large holes a common instrument is the spill gauge', which is a solid bar of determined length having domed ends.

Whilst the hole may be within the tolerances of the gauge there is difficulty in detecting distortion, or an outof-parallel condition of the bore. An . instrument which will check up on such conditions is the internal micrometer, which Will give readings of a fine degree of accuracy so long as it be maintained in strict adjustment. After a micrometer has been in use over a long period it will probably be

found that the thimble can be taken past the zero mark when the measuring faces on the spindle and the anvil are together... Provision for correcting this is not difficult to arrange, the procedure varying with the particular make of instrument.

In the case of lateral adjustment, however, the matter is not so straightforward and, in point of fact, means for effecting this is usually lacking. In a new micrometer head, which is covered in patent No. 554,429; by British Timken, Ltd., and R. Treen, a simplified means for carrying out both rotary' and lateral adjustment is described, and micrometers embodying the idea have for some time been in use by British Timken, Ltd.

. The method is based on providing an easily operated means for locking the thimble in new rotary and lateral positions on the spindle following the insertion of a shim, or shims, between a flange on the spindle and an internal flange on the thimble. Locking is effected by screwing up the cap on the head of the thimble. This presses together two split collars, one, having a conical exterior, lying in the conical interior of the other.

The location of these collars is between the spindle and the interior of the thimble, and under pressure of the cap they expand and lock the two elements securely together in their new positions following correction.

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