To establish the pitch diameter of a thread ring gage it is accomplished by adjusting the thread ring to a truncated thread setting plug gage. Make sure the setting plug gage has been recently calibrated and has current certification.
Follow this step by step instruction on how to set a thread ring gage and ensure the pitch diameter setting is correct:
- Thoroughly clean both gages and visually inspect them to make sure there are no nicks or burrs
- Lubricate the setting plug with a thin film of oil before assembling it with the thread ring gage
- Loosen the locking screw of the thread ring but do not remove it from the gage
- Turn the adjusting screw on the thread ring clockwise to open the ring to a larger pitch diameter than the truncated setting plug gage
- Turn the ring onto the setting plug until it is completely engaged with at least one thread of the ring extending beyond the last thread on the back end of the full form section of the setting plug. By doing this it will provide uniform wear over the entire thread length of the setting plug gage
- Now turn the adjusting screw counter-clockwise until there is a slight drag between the thread ring gage and the setting plug
- Turn the locking screw clockwise until tight, this locks the adjusting screw so that the pitch diameter of the ring remains fixed. There should now be a noticeable drag between the ring and setting plug
- Unscrew the setting plug gage from the thread ring gage
- Screw the setting plug into the thread ring gage approximately 1 1/2 turns and try to move it from side to side to test the ring for a taper condition. When checking for shake be sure to use light pressure on the setting plug gage to avoid any damage to the threads of the gage
- Screw the thread ring gage over the truncated and full form sections of the setting plug gage. The feel should remain about the same as in the previous step. You may feel a little more drag at the full form engagement because of more flank contact
- Remove the setting plug from the thread ring gage and repeat this step on the other side of the ring gage
- The assembly of the thread ring gage and the setting plug should feel the same from both sides of the thread ring. This will insure that you have a straight pitch diameter
- When the ring gage is set to the setting plug with uniform feel over the entire length of the plug, including there being no end thread shake, it is then correctly fitted with the setting plug gage. Keep in mind that because of tolerances in the manufacture of both the thread ring gage and the setting plug gage that unless they are made at the same time to be matched with each other, allowances must be made in the assembly feel or fit to compensate for any slight differences. For example, a slight difference in angle or lead can cause more of a tightening or drag at full engagement than over partial engagements. This is not a serious condition as both the thread ring gage and the truncated setting plug gage may well be within required specifications
- If the thread ring gage is set to the truncated portion of the setting plug gage first instead of the reverse procedure described above and it fails to pass over the first full thread of the full form section of the setting plug gage, this would indicate a major diameter interference in the thread ring gage. It should be replaced with a new gage otherwise the thread ring will not engage properly
If you have any additional questions, please feel free to contact us at 888-400-4243, email us at info@westportcorp.com or visit us at www.westportcorp.com
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