Best Practices for Test Indica tors and Holders Test indicators are primarily used for testing or checking parts and for machine setups. They are a tool that is indispensable for working as a machinist or toolmaker. They are available in two types – plunger style and the lever style. Both are versatile, but the lever style can be more adaptable to smaller, confined working areas. Unlike other indicators, the lever style's contact moves in an arc rather than in a straight line. This can cause a slight inaccuracy called "cosine error" if the angle of the lever to the workpiece is too steep. If, for example, a lever was set off an additional 20º, there could be an error of .0006" in a .010" range (0.012 mm in a 0.2mm range). It is good practice, therefore, to keep your contact at or near 90º to the direction of movement. Test indicators should always be "loaded" 1/10 to 1/4 of a turn before measuring. Test indicators are comparative instruments that check and compare to known standards or that are used to zero-out setups. We have a broad selection of holders shown in this section that allow you to use these indicators to the fullest. We've never seen a job that one of these holders combined with one of our test indicators could not handle. Dove Tail Style Snugs: PT22428: 3/32-1/4" (2.4-6.3mm) inch hole on one side and standard female dove connection on the other. For use with 708, 709 and 811 Test Indicators. Allows connection to 657AA, 657A, 657T Magnetic Base and PT017762 Holding Rod for 252 Height Stand and PT11770A Tool Post Holder or 711-49 Height Gage Attachment. 657H PT22428 58S 657R PT16846 665D 657S PT18718 PT18724 57S 665L For extreme accuracy we recommend positioning the lever contact so that it is approximately 15º (708/709) or 0º (all other lever styles) from being horizontal with the workpiece Test Indica tor Snugs and Split Bushings Usage Guide INCORRECT CORRECT Round Connection Sungs: 657S: 1/4" hole on both ends PT18718: 3/32-1/4" hole on one end 5/16" on the other PT18724: 3/32-1/4" hole on one end 3/8" on the other 657H: 3/8" inch hole on both ends 665D: 3/8" inch hole on one end .465" (11.8mm) on the other. Includes 665L (.375" bushing) PT16846(notshown):3/4"inchholeonbothends Universal Style Snugs: 58S: 3/32-1/4" hole allows connection to 1/4", 5/16", 3/8" (6.3, 8, 9.5mm) Universal Drum Style Snugs: 57S: 5/16" and 3/8" (8, 9.5mm) on one end and 9/64", 5/32", 3/16", 1/4" (3.5, 4, 4.8, 6.3mm) on the opposite NOTE: 3/8-1/4" bushings can be used with some of the snugs above to change 3/8"-1/4" where required (see PT00764) Split Bushings: 657R: outside .312" (7.9mm), inside .250" (6.3mm), length 1.000" (25.4mm) PT00764: .375" (9.5mm) outside, inside .250" (6.3mm), length 1/2" (12.7mm) 80SB: outside .375" (9.5mm), inside .219" (5.5mm), length 1/2" (12.7mm). Used to increase the stem diameter on Starrett 80 miniature indicators to standard .375" diameter. 25MSB: outside .375" (9.5mm), inside .316" (8mm), length 1/2" (12.7mm), converts metric stemmed indicator to standard 3/8" diameter 665L: outside .465 (11.8mm), inside .375" (9.5mm), length 1-1/4" (31.5mm) 25SB: outside .500" (12.7mm), inside .375" (9.5mm), length 1/2" (12.7mm) 134 I ndica tors and G ages