A common need in auto work is to deal with sensors having 1/8 x 27 NPT male thread such as OEM pressure switches and aftermarket gauge kits. Just solved a problem with a supplied sensor which would not start into the engine block female because the new sensor measured .020" larger along the taper than the one removed. After stewing around and double checking the threads between the two sensors I turned to the two 1/8 - 27 dies I had. One an older Craftsman with split design allowing some adjustment on "fit," and another solid one in a metric set without that feature. It appeared that the metric die might reduce the diameter problem so I carefully lubed and ran that die on the "oversized" gauge male. That reduced the diameter of the thread and allowed it to enter the block female.
Why is there variation die to die? Being tapered it seems the die manufacturers ( in this case at least) chose two different points along the taper to form their dies??? I know there are classes of fit for straight threading, but this experience reminds me of how threading is done on a lathe with the final being checked with a die???
Why is there variation die to die? Being tapered it seems the die manufacturers ( in this case at least) chose two different points along the taper to form their dies??? I know there are classes of fit for straight threading, but this experience reminds me of how threading is done on a lathe with the final being checked with a die???
