Abstract: Methods and devices are provided for accurately determining depths of certain structures in downhole strings. Locator tools comprise a shaft and a plurality of locator springs longitudinally mounted on the shaft. The locator springs are biased to expand and are configured to compress to allow the tool to traverse past restrictions in the downhole string. Each locator spring includes a locating pad that allows it to engage with an internal locating notch in the downhole string. The internal locating notch is sized to mate with the locator tool, i.e., to allow the locator springs to engage the internal locating notch. In this way, the depth of internal locating notches may be determined precisely and accurately by sensing engagement of the tool with the internal locating notch. Advantages of certain embodiments include more accurate depth determination, repeatable engagements of the tool, and reduced false engagements.

Abstract: Methods and devices are provided for accurately determining depths of certain structures in downhole strings. Locator tools comprise a shaft and a plurality of locator springs longitudinally mounted on the shaft. The locator springs are biased to expand and are configured to compress to allow the tool to traverse past restrictions in the downhole string. Each locator spring includes a locating pad that allows it to engage with an internal locating notch in the downhole string. The internal locating notch is sized to mate with the locator tool, i.e., to allow the locator springs to engage the internal locating notch. In this way, the depth of internal locating notches may be determined precisely and accurately by sensing engagement of the tool with the internal locating notch. Advantages of certain embodiments include more accurate depth determination, repeatable engagements of the tool, and reduced false engagements.