Thread Quality Control Series: Powered Gaging of Tapered Pipe Threads

Pipe threads are manufactured in many forms, but the most common types are straight and tapered threads. Straight pipe threads are gaged with the “GO” & “NO GO” process like regular threads, but tapered pipe threads require an entirely different gaging method: A series of L checks.

The 3 main types of L checks are the L-1, L-2 (for external threads) or L-3 (for internal threads) & the 6-Step Check. To learn about these checks in detail, visit our post detailing the Hand Gaging of NPT Threads: Hand Gaging of NPT Threads. In this video, we will be focusing on the L-1 check, as it is the most common check used in powered pipe thread verification.

The Powered L-1 check is not materially different than that in hand gaging. The process starts by running a tapered thread gage member into or onto a part’s threaded feature to the point of stall. If the thread is good then the gaging flat or notch will be between one turn high and one turn low relative to the end or face of the part. To achieve this, the thread-verification unit uses two sensors to track the position of the gage. These will indicate that the gage has gone far enough, but not too far.

There are two methods of L-1 gaging depending on the condition of the parts: Single-Step or 2-Step. For most applications, single-step is sufficient. This consists of running the gage into or onto the thread just once. Occasionally, parts are rough or dirty enough to the point where the 2-step process is required. The 2-step process works like this: First the TGM is run in (or on) to stall at a high torque level, for a ‘seating’ (or conditioning) cycle. Then the TGM is backed away slightly and then run in (or on) a second time for the ‘gaging’ cycle, at a torque level that is lower, in order to correspond to what would be expected of hand gaging.

Just as with “GO” and “NO GO” thread verification, powered gaging of tapered pipe threads adds speed, efficiency, and accuracy to your quality control process while still providing results correlatable to hand gaging.

Contact one of our Applications Engineers today to learn how New Vista’s Thread Verification Systems can improve your pipe thread gaging process.