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Before drill pipe can be screwed onto the drill collars, a special short length of pipe with a
drill pipe connection on the top and a drill collar connection on the bottom is added. These special short pipes are
called subs and if it is used to convert one size or type of connector to another, it is called a crossover sub. When
the sub connects the drillb it to the lowest drill collar it is called a bit sub. (Seen Left)
Bit Brokers International Rotary Substitute Adapters (Subs) are made to any length, outside diameter (O.D.),
inside diameter (I.D.), and thread combination. 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. Subs can be made with a breakout
configuration for any rig. 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.(Seen right)
Weld-on or Thread-on Tool Joint Subs are designed with one end to shrink fit or screw onto the end of your drill tube
and then be welded. The opposite end is the pin or box connection of your choice. Pin or Box to Blank Subs are similar in use to the above subs.
They have a blank face, either solid or with an I.D. on the end opposite the pin or box connection. (Seen left)
Kelly Saver Subs refer to a sub used between the Kelly or top head drive and the drill pipe. It is usually a pin to pin sub
that takes the wear abuse to protect the drill pipe and the drive connection. (Seen right)
Float Valve Subs are bored to a larger I.D. to suit a Float Valve. They can be placed anywhere in the drill
string to maintain the circulation in one direction. (Seen left)
Elevator Lift Subs are narrow-necked subs which provide a lifting area for use with standard pipe elevators.
They are commonly used with internal flush (IF) pipe. (Seen right)
Jet Subs are designed with the water flow to jet out the sides of the sub to assist cleaning the perforated pipe or screen.(Seen left)
Shock Subs are specialized subs designed to absorb the shock vibrations created by a down-hole hammer and to prevent
damage to the drill string and the top head drive.
Floating or Cushion Subs absorb shock vibrations transmitted up through the drill string built to protect the pipe.
Their construction is simpler with more vertical movement in the sub.
Special ID Subs are bored to a special I.D., either smaller or larger than the standard or for special cases with no I.D. bore.
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).
Flats depth 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.
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 you 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:
A. The diameter of the base of the pin where it meets the sub body (shoulder).
B. The thread length. Measured from shoulder to the end of the tool joint.
C. 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).
D. The thread form (taper, square, acme, special, etc.)
E. The material O.D. - this may differ within threads, but is a cross check.
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