Rotary Sub Adapters Overview

Mills Machine Rotary Substitute Adapters (Subs) are made from 4142 heat-treated alloy steel. They are made to any length, outside diameter (O.D.), inside diameter (I.D.), and thread combination. We stock the most common subs and carry a large inventory of steel to custom manufacture any sub you need. Subs can be made with a breakout configuration for any rig. Unless otherwise specified our standard flat is 2" long and 3/8" deep per side. We can manufacture single flats, double depth flats, extra long flats, beveled flats, and custom flats. Breakout lugs are also available. Flats or lugs normally add to the length of the sub. The outside and inside diameter of the sub should match up to the drill rod that you are using. Always be aware of the largest O.D. and the smallest I.D in your drill string.

When going from a larger connection to a smaller connection, a bottleneck may be furnished to reduce the weight of the sub and make it easier to breakout. The bottleneck is normally cut on a 45° angle and may add length to the sub. Any box thread can be bored out to accept a float (check) valve. The valve will add length to the sub depending on the length of the valve. The valves are sized to the box thread and can be seen in the last section of this catalog (Misc. Drilling Accessories). Bored-out subs can be furnished with a float valve installed. Mills Machine stocks thread gages for over 600 different tool joint connections for use in the water well, construction, mining, utility, horizontal, geo-thermal and environmental drilling industries. The threads are manufactured to meet the specifications of the American Petroleum Industry or the Diamond Core Drilling Manufacturers Association.

Undefined Tool Joint Measurements

Often we come across undefined tool joints. The thread identification is normally stamped on the tool joint. If that stamp is worn or is not present we will need specific information to determine the tool joint identification. The way to define the pin tool joint (The box tool joint is hard to measure and measurement has often lead to errors) is to measure:

  1. The diameter of the base of the pin where it meets the sub body (shoulder).
  2. The thread length. Measured from shoulder to the end of the tool joint.
  3. The number of threads per inch - put the 0 mark of a ruler on the center of the first thread, don't count that thread, then count the threads to the one inch mark (see sketch).
  4. The thread form (taper, square, acme, special, etc.)
  6. The material O.D. - this may differ within threads, but is a cross check.

Your free thread ruler is at the beginning of this catalog. It will assist you in determining the thread. If you need additional copies, please contact your sales representative. If there are problems measuring the part, send it to our engineers who can match the tool joint with one of over 600 thread gages we have in stock or in the API reference books.

Sub Measurements

 Subs have two length measurements. The first is the Over-All-Length (OAL), this is the length from the tip to tip of the sub - the longest dimension of the sub. The second is the Shoulder-to-Shoulder (S to S) or Working Length (WL), the working dimension of the sub in the drill string. It is measured from the shoulder face of the pin to the shoulder face of a pin on pin to pin subs (1.). On a pin to box sub it is measured from the shoulder face of the pin end to the end of the box end (2). On a box to box sub the OAL and S to S are the same (3).

Flat Measurements

 Flats depths on subs may be measured in two different ways. The first, and most common, is by the depth of the flat from the diameter of the sub (1), how much material is removed. The second method of measurement is to measure the distance between the flat surface to flat surface (2), or the opening of the pipe-handling tool. If the flat has a taper, please give us the length at the top and again at the bottom of the flat.