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Crossover Subs
Field Proven
Custom manufactured to connect virtually any combination of API or premium thread connections.
Used throughout drilling, fishing, milling, cleanout, and well intervention operations.
Frequently specified for custom bottom-hole assemblies and specialty downhole tools.
Machined to tight tolerances for dependable fit and performance.
Crossover subs may appear straightforward, but they become a critical structural link in the bottom-hole assembly. Precision machining, proper thread geometry, and material quality all contribute to maintaining the integrity of the work string under demanding downhole loads.
Engineer's Note
Bull Dog manufactures Crossover Subs to bridge different connection types and toolstring sizes, including Box x Pin, Pin x Pin, and Box x Box configurations. Machined in-house to tight tolerances, each sub is made from heat-treated steel or customer-specified materials. Available in standard API and premium thread forms.
No two bottom-hole assemblies are exactly alike. Bull Dog manufactures custom crossover subs because reliable downhole operations depend on properly matched connections—not forcing standard components to fit specialized applications.
Why We Built It
Applications
Connecting dissimilar thread types between two components in the drill string.
Acting as a Saver Sub to protect the threads of drill pipe or other expensive components from excessive wear.
Positioned between the entry side swivel and the first pipe joint to absorb wear during tripping operations.
Used as a Bit Sub to connect the drill bit or other bottom-hole tools to the string while enabling reverse circulation.
Reducing replacement costs by serving as a sacrificial, easily replaceable component.
Versatile integration with a variety of drilling, milling, or fishing assemblies requiring non-matching thread connections.
Features & Advantages
Thread Compatibility: Custom-built to match a wide range of thread profiles (pin x box, box x box, pin x pin).
Cost-Effective Protection: Acts as a wear component to safeguard expensive drill pipe and bottom-hole equipment.
Durable Construction: Manufactured from high-strength steel for long-lasting performance under harsh downhole conditions.
Easy Replacement: Designed for quick and inexpensive swap-outs on site, reducing downtime.
Multi-Purpose Use: Functions as a Saver Sub, Bit Sub, or thread connector depending on the job requirement.
Improved Tool Longevity: Minimizes wear and tear on primary tools and pipe, extending their service life.
Custom Sizing: Can be manufactured to customer specifications for length, thread type, and diameter.
Reverse Circulation Ready: Certain configurations allow efficient fluid or air flow to the bit face during operations.
Specifications
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Bull Dog can manufacture any type of crossovers your company requires. Please specify OD x ID x Bore along with connections.
Premium connections are available:
Frequently Asked Questions (FAQs)
What is a Bull Dog® Crossover Sub used for?
A Crossover Sub is used to connect tools or tubulars with different thread types or sizes. It allows components with mismatched connections — like drill pipe to workover tools, or bailers to mills — to be safely and securely run in the same string.
What types of threads and sizes can Bull Dog match with a crossover?
Bull Dog can manufacture Crossover Subs with virtually any combination of API or premium threads, including:
EUE / NUE
IF / REG
Line pipe
Left- or right-hand threadsSubs are available in sizes from ¾" rod connections up to 9" O.D., depending on your downhole hardware.
Are Bull Dog Crossover Subs built for high-strength applications?
Yes — all Bull Dog Crossover Subs are machined from high-strength, heat-treated alloy steel and designed to maintain full tensile and torsional integrity. We don’t cut corners — every sub is built for field abuse and certified for the job.
When should I use a crossover sub instead of a full string change?
Use a crossover sub when you need to:
Adapt new tools into an existing string
Connect differently threaded components
Avoid unnecessary rethreading or inventory changes
Minimize rig time while keeping the BHA moving
Can Bull Dog Crossover Subs be customized?
Absolutely. We offer custom thread matching, hardfacing, pressure testing, and rotational specs on request. Whether you're dealing with a legacy connection or a custom-built tool, we’ll machine a sub that makes it work.
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Want To Know More About This Tool?
We are ready to help! If you're interested in one of our tools, or if you have a job in mind that needs a custom tool solution, don't hesitate to reach out and we'll be ready to get you exactly what you need - faster than you can get it anywhere else!