The Starrett® 579 telescoping gage is used for determining the true size of holes, slots and recesses upto 6 in. The ends of both contacts are hardened and ground to a radius to allow proper clearance on the smallest hole the gage will enter. The tool must be slightly "rocked" in the hole being measured to ensure that the tool is on the proper diameter before it is locked and withdrawn. The final hole size is obtained by measuring over the gage contacts with a micrometer.

Starrett® Telescoping Gage, Self-Centering, Series: 579, 5/16 to 1/2 in Measuring, Rigid Handle, Steel, Satin Chrome, 12.796 in L x 0.281 in W x 0.507 in H Dimensions

• Ends of both contacts are hardened and ground to a radius to allow proper clearance on the smallest hole the gage will enter
• Two telescoping contacts
• Precision ground radius on each gage provides two-point contact for maximum accuracy
• Greater range
• Constant spring tension gives uniform contact pressure
• Both plungers are easily locked at any desired setting
• Handles can be individually ordered, handles longer than 12 in (300 mm) are available on special order
• Handles are rigidly attached to the contact plungers and are automatically self-centering

• https://externalassets.unilogcorp.com/ASSETS/DOCUMENTS/ITEMS/EN/Starrett_579A_12_Full_Engineering_Drawing.pdf https://externalassets.unilogcorp.com/ASSETS/DOCUMENTS/ITEMS/EN/Starrett_579A_12_Full_Engineering_Drawing.pdf