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, and environmental drilling industries. The threads are manufactured to meet the specifications of the American Petroleum Industry or the Diamond Core Drilling Manufacturers Association.