L2 & l3 Gages

After using the L-1 gage the L2 ring or L3 plug is assembled with the part and must stop within 1/2 turn plus or minus of where the L1 stopped.  The L-2 ring and L-3 plug are designed to clear the threads of the part that the L-1 contacted with and contact with the threads further onto or into the part. This measures the taper of the thread on the part by comparing the front threads and the back threads.  If the taper is too severe or too straight, the L-2 ring or L-3 plug will not stop within 1/2 turn from the point where the L-1 stopped.

Remember the L2 and L3 are to check taper only not size.