Lead Gages

Buttress Lead Gages

Lead Gages - Lead Gages

Thread Lead

Thread Lead is probably one of the most important thread elements if not the most important in the thread cutting industry. Lead error (which often leads to standoff error on tapered threads) is the most common error generated by manual and CNC lathes not cutting properly. Worn ball, lead screws, Z axis servo drives and spindle encoders on threading lathes will permit the cutting tool to stall, slow down or lag, which causes the thread pitch to be shorter than programmed on the first and second threads. This in turn results in lead error…standoff error… and eventually a failed connection.

The lead gage inspects thread lead using contact points that seat in the threads of a part. Thread lead is the distance between threads, measured on a plane parallel to the centerline of the threaded part. The pitch of the thread determines the diameter of the contact points required for taking measurements.

Thread Lead Gages inspect both internal and external thread lead for a variety of thread forms and provide dimensional verification of product print data on the integrity of your threads. Gagemaker has both two-point and three-point system lead gages that are designed to accurately inspect lead for ACME, Stub ACME, UN, and API threads.

Inspecting lead is a highly recommended practice industry wide for both straight and tapered thread manufacturers and it is a required inspection by the American Petroleum Institute for line pipe, rotary shouldered connections and casing and tubing.

The LG-6001 and the LG-6002 use a two-point system to inspect thread lead for straight and tapered threads. The LG-6002 inspects both external and internal threads, while the LG-6001 inspects external threads. The two point system allows for a sweeping action to obtain the measurement. Both gages are available with higher resolution indicators.

The LG-5003 uses the three-point system to inspect internal and external thread lead. Two fixed contact points at the rear of the gage and one moveable contact point at the front of the gage provide complete stability when taking thread lead measurements. This unique design does not require sweeping to obtain measurements.

Contact points can be easily changed to allow the gage to be used on a variety of thread forms. Each gage comes with a default set of contact points, but customer may specify another set.

Before inspecting parts, the lead gage must be preset to a nominal predetermined dimension using a lead gage setting standard. Lead standards are available for both straight and tapered threads. Our setting standards are manufactured according to ANSI and API specifications, respectively.


  • Uses a three-point system for greater stability when inspecting parts (LG-5003).
  • Uses interchangeable contact points to allow inspection on a variety of thread forms.
  • Requires presetting using Gagemaker’s lead gage setting standards
  • Supplied with one set of contact points. Customer may specify points.

*TPF = Taper Per Foot, TPI = Threads Per Inch