Definition
Crossover Sub — A crossover sub is a short threaded sub that connects two tubulars with different connection types or sizes — a box of one thread on one end and a pin of another on the other — allowing otherwise incompatible components to be joined in the drill string.
Also known as: crossover sub, X-over sub, XO sub, crossover
What a crossover sub is
A crossover sub (X-over) is a machined sub whose two ends carry different rotary-shouldered connections, letting components that would not otherwise make up be joined together. For example, a crossover might present an NC50 box on top and a 6-5/8 REG pin on the bottom to connect drill pipe to a larger drill collar.
Crossovers are ubiquitous in the bottomhole assembly, where drill pipe, HWDP, collars, stabilizers, subs and the bit frequently use different connection types and sizes.
Key points
- Two connections — one box and one pin, each a specified thread and size.
- Full-strength — machined from heavy bar so the sub is not the weak point in the string.
- Fishing profile — kept smooth and gaugeable so the sub can be latched if it must be fished.
Renting crossovers
Because BHAs mix connection types, crossover subs are a standard rental item stocked in many thread combinations. Explore BHA components and drill collars, or contact us with the two connections you need to bridge.