Sub Adaptors of Hole Drilling Tools
A Sub Adapter, a special short length of pipe with a drill pipe connection on the top and a drill collar connection on the bottom, is added before a drill pipe can be screwed onto the drill collars.
Cross over subs act as an intermediary between two dissimilar threads and are used to connect the two. There are some other uses for cross over subs as well. A crossover sub can be used to protect other tooling in your drill string. Since the cross over sub is the least expensive item in the drill string it can be designed to wear before any other drilling component does. In this application a Cross over sub is often called a SAVER SUB. The Saver Sub is used to connect the entry side swivel to the first piece of pipe and is attached to every pipe, going in and coming out. This position in the string is subject to much wear, so saver sub was designed to be an inexpensive, easily replaceable part. As such, it is used to protect the threads on the actual pipe and allows for a quick and onsite replacement. Using saver sub offers great advantages, as it is cheaper to change a saver sub often, than to buy new pipe once.
A cross over sub can also be used just above the bit or in a reverse circulation application to deliver outgoing air to the bit face. In these applications a cross over sub is usually called a BIT SUB.
All of our cross over subs can have wrench flats milled into them to allow for better assembly and disassembly.