Key to St arrett Micrometer Numbering System Starrett Micrometer Accuracy Standards (Unless Otherwise Noted on the Catalog Page) Type Range Readout Accuracy Mechanical 1" .001" ±.0001" 1" .0001" ±.00005" 25mm 0.01mm ±0.002mm 25mm 0.001mm ±0.002mm Electronic 1" .00005" ±.0001" 25mm 0.001mm ±0.002mm Key to Starrett Micrometer Numbering System Prefixes R Reverse Reading S Micrometer Set T .0001" Reading V 0.001mm or 0.002mm Reading,as specified Suffixes F Friction Thimble L Lock Nut M Metric N Non-Rotating P Plain R Ratchet Stop S Speeder TN Threaded Hub and Check Nut W/SLC Standard Letter of Certification X Micro-lapped Carbide Measuring Faces Z With Case ZZ Case Only How to Adjust St arrett Micrometers Adjustments to Starrett Micro­ meters are rarely needed; however, if it becomes necessary, they can be readily adjusted in two easy operations as follows: 1. If any play should develop in the spindle screw threads due to wear of the spindle nut after long use, first back off the thimble, insert the spanner wrench in the slot of the adjusting nut and tighten just enough to eliminate play. Illustration shows how easily this is done. 2. After carefully cleaning all dirt or grit from the measuring faces of anvil and spindle, bring them together and insert the spanner wrench in the small slot of the sleeve. Then turn the sleeve until the line on the sleeve coincides with the zero line on the thimble as shown. Micrometer Quality and Accuracy Product quality and accuracy cannot be valid unless referenced to a quality and accuracy standard. All Starrett precision measuring tool standards meet or exceed accuracy and performance specifications of national and international standards and are traceable to the National Institute of Standards and Technology. The Starrett Company does not rely on statistical sampling inspection. Every precision measuring tool is individually inspected. All Starrett micrometers have the same accurate heads as outlined in the chart. Inaccuracies because of size can be minimized if the tools are set accurately to standard, and measurements are carried out in a similar position with similar pressure. Measuring Tips from Our Experience • Most obvious to everyone is to keep the work to be measured and the micrometer anvil and spindle faces clean. • For very fine measurements, the micrometer should be set to zero or to a standard by your "feel", by the friction thimble, or by the ratchet, whichever you will be using. • The most popular micrometer option has been the ratchet speeder because it does three things well: it speeds opening and closing, it applies uniform pressure from the ratchet, and it allows for using the thimble for individual "feel". • The speeder is helpful because it takes forty turns to cover the range of a typical English- reading tool and fifty turns to cover the range of a metric-reading tool. • Large micrometers especially should be set to a standard in the same approximate position in which they will be used, that is, vertical or horizontal, to minimize any frame flexure influence. • Too much speed in approaching the work will result in an inaccurate measurement. • If the micrometer has been set to a flat standard, you can get approximately .0001" (0.0025mm) difference when measuring over a round because the same pressure is being applied to a point or line contact. • Carbide or hardened steel measuring faces are a matter of choice. Carbide wears longer but many craftsmen think they get a better "feel" with highly finished steel measuring surfaces. • Insulating pads on micrometers are a matter of personal preference. With the Starrett balanced micrometer design, there is no need for insulation. Insulation from hand heat is usually more beneficial on long sections, such as end measuring rods. 21 M icrometers