Volume 2, No. 1 Spring 2008

|Front Page| |<Previous| |Next>|  Quality, Precision, Innovation

Inside Micrometers Provide Precise Measurement of Inside Dimensions

Inside Micrometers are an application of the micrometer screw principle to adjustable-end measuring gages. The distance between ends or contacts is changed by rotating the thimble on the micrometer head up to the extent of screw length, usually either one-half or one inch. Greater distances are obtained by means of extension rods and suitable spacing collars or gages that slide onto the holding end of the interchangeable rods in various combinations to cover the total range of the tool. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Inside micrometers are a little more challenging to use than outside micrometers. With spherical contact points more practice and caution is needed to “feel” the full diametral measurement. Since one contact point is generally held in a fixed position, the other must be rocked in different directions to be sure the tool is spanning the true diameter of a hole or the correct width of a slot. In place of a locknut, a friction drag is noticeable on the thimble. Measuring rods can be individually adjusted to take up wear, and the micrometer head is also adjustable for wear on its screw. A knurled extension handle is available for obtaining inside measurements in hard-to-reach locations. End Measuring Rods Precise setting of the slides and table on jig borers and other machine tools are held to a high degree of accuracy by means of precision end-measuring rods. Each set consists of two micrometer heads graduated in “tenths” (.0001") together with a series of hardened, ground and lapped measuring rods. Fixed Range Inside Micrometers Starrett fixed range inside micrometers are available in either 1 inch or 2 inch range and up to 12 inches in length. Insulating handles minimizes possible expansion by heat when held in the hand.

Spring 2008 |Front Page| |<Previous| |Next>| Quality, Precision, Innovation

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