How do you use an external thread taper gauge?
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1.Definition
For round threads and line pipe threads, taper shall be defined as the increase in the pitch diameter of the thread, in inches per inch (millimeter per millimeter) of the thread. For buttress threads, the taper is defined as the change in diameter along the minor cone of the external threads and the major cone of the internal threads. On all threads, taper tolerances are expressed in terms of “inch per inch of the thread” (“millimeter per millimeter of the thread”) and taper deviation shall be determined accordingly. The measurements are made for the specific interval lengths and the observed deviation shall be calculated to the inches per inch (millimeters per millimeter) basis.
2. Gauge Contact Points
The contact points of taper gauges shall be of the ballpoint type with diameters in accordance with the following table. For line pipe and round threads, the diameter of the contact points are such that they contact the thread flanks at the pitch cone, approximately, rather than the minor cone. For buttress threads, the dimensions of the contact points are such that they contact the minor cone of external thread and the major cone of the internal thread.
3. Procedure (Taper Gauge)
The taper of external threads shall be measured with a taper gauge.
The ballpoint on the fixed end of the gauge shall be placed in the groove at the first perfect thread position and the ballpoint on the plunger in the groove diametrically opposite. The fixed point shall be held firmly in position, the plunger point oscillated through a small arc, and the dial indicator set so that the zero position coincides with the maximum indication. Similarly, successive measurements at the same radial position relative to the axis of the thread, shall then be taken at the required intervals for the full length of threads for buttress threads or the full length of perfect threads for tubing and line pipe threads and the TECL for round thread casing. The difference between successive measurements shall be the taper in that interval of threads. The taper in the last interval of perfect threads shall be measured.
External Thread Taper Gauge
Typical External Thread Taper Gauge
4.Run-Out (Buttress Only)
The run-out gauge (see Figure 13) shall be used to check the run-out thread root and ensure that the external thread is sufficiently long and is a true runout thread. The run-out gauge indicator shall be set to zero using a flat surface as a setting standard for size 133/8 and smaller. For size 16 and larger casing, the run-out gauge indicator shall be set to zero using the perfect thread roots as a setting standard. These perfect thread roots shall be checked for acceptable taper prior to setting the run-out gauge.
5. Procedure (Run out)
If the last thread groove is less than or equal to the distance from the end of the pipe to the apex of the makeup triangle (A1 +0.375 in. 9,52 mm]), the thread must be a true run-out thread. The thread run-out shall be measured where it terminates or at the apex of the make up triangle, whichever is the shortest length, by placing the run-out gauge contact point at 90 degrees prior to the thread termination or the apex of the triangle, and rotating the run-out gauge clockwise until the contact point is out of the thread groove or beyond the triangle apex. If the dial indicator reads +0.005 in. (+0,13 mm) or less, the run-out is acceptable.
Buttress Run Out Gauge
Typical Run Out Gauge for Buttress Thread Casing
How to Order?
When you order, please let me just know the thread type and range need be measured, we will provide you the best solutions and best quotations. More details or any questions please contact: sales@fyougauges.com or WhatsApp/Wechat: +86 13962168423
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