Integral construction
Machined from a solid alloy-steel bar, trepanned, drifted and threaded.
DRILL STRING PRODUCTS
Drill Collars
Precision-machined drill collars for weight-on-bit, stiffness and bottom-hole assembly stability.
StandardAPI 7-1 · API 7-2 connection references
Size / supply rangeOD, ID, overall length and unit weight coordinated to the BHA · Slick and spiral profiles
Grades / materialsAISI 4145H Modified typical route · Non-magnetic variants managed as a separate material route
Connections / optionsAPI NC connections · Selected project-specific rotary-shouldered connections
BHA WEIGHT & STIFFNESS
Heavy-wall drill-stem components engineered around weight on bit.
Drill collars are integral, thick-wall components positioned in the bottom-hole assembly. They provide weight on the bit, help keep the drill string above the BHA in tension, transmit torque and drilling fluid, and contribute to stiffness and directional behavior.
OAK’s original product range identifies AISI 4145H modified steel, full-length quench-and-temper heat treatment, slick and spiral configurations, and a stated outside-diameter range of 3⅛–14 inches. Final dimensions and mechanical acceptance criteria are confirmed against the purchase specification.
Full-length heat treatment
Specified to develop consistent toughness and mechanical properties through the section.
Application-led geometry
OD, ID, length, spiral profile and connections are selected as one BHA component.
Connection integrity
Thread form, stress-relief features, cold rolling and surface treatment are order-critical details.
ORDERING SPECIFICATION
Define the complete collar—not only the outside diameter.
The table separates OAK’s stated product basis from common international procurement fields that require order confirmation.
| Product reference | API 7-1 Series Drill Collar |
|---|---|
| Primary reference | API Spec 7-1; rotary-shouldered connection dimensions commonly reference API Spec 7-2 |
| Material stated by OAK | AISI 4145H modified alloy steel, quenched and tempered |
| Configurations stated by OAK | Slick drill collar and spiral drill collar |
| OD range stated by OAK | 3⅛–14 in.; availability, bore and connection combinations are confirmed per enquiry |
| Length | Common purchasing references include approximately 30 or 31 ft; exact overall length and tolerances must be specified |
| Connections | NC, REG and other specified rotary-shouldered connections, subject to dimensional compatibility review |
| Optional features | Spiral grooves, slip recess, stress-relief features, thread-root cold rolling, phosphate coating, hardbanding and special surface finish as agreed |
The OAK range is the product basis. Industry references shown here support enquiry preparation and do not replace the final data sheet, drawing or purchase order.
MATERIAL & PROPERTIES
AISI 4145H modified steel with section-sensitive acceptance.
OAK identifies full-length heat treatment and metallurgical verification as central to uniform toughness and durability. Mechanical values below are common industry purchasing references and must be confirmed for the ordered size and specification.
| Nominal OD group | Minimum yield strength | Minimum tensile strength | Minimum hardness |
|---|---|---|---|
| 3⅛ through 6⅞ in. | 110,000 psi / 758 MPa | 140,000 psi / 965 MPa | 285 HBW |
| 7 in. and above | 100,000 psi / 689 MPa | 135,000 psi / 931 MPa | 285 HBW |
Reference values reflect a widely used industry drill-collar specification. The applicable API edition, test method, sampling location, upper hardness limit and any supplementary impact requirement belong in the enquiry.
CONFIGURATION & CONNECTION
Geometry, handling and fatigue details work together.
Configuration should be selected around hole conditions, BHA design, rig handling practice and connection compatibility.
Slick drill collar
As-rolled or specified finished OD for conventional BHA weight and stiffness.
Spiral drill collar
External spiral grooves reduce wall-contact area and support drilling-fluid flow around the collar, helping mitigate differential sticking.
Stress-relief features
Pin stress-relief groove and box boreback may be specified to reduce stress concentration adjacent to engaged threads.
Connection finishing
Thread-root cold rolling and phosphate treatment may be specified to support fatigue and galling resistance.
Handling provisions
Slip recesses or lift-sub requirements must be coordinated with the applicable standard and the rig’s handling plan.
Special configuration
Non-standard OD/ID, bore profile, hardbanding or drawing-based machining requires technical review before quotation.
DIMENSIONAL RECORD
Twenty-three common configurations are maintained in the OAK working table.
| Common recorded OD range | 3⅛–11 in. across the structured working table |
|---|---|
| Fields maintained | OD, ID, connection, overall length, bevel diameter and bending-strength ratio |
| Broader stated supply range | Selected OAK source material states availability through 14 in.; confirm the exact combination before quotation |
| Release basis | Approved drawing, applicable API edition and purchaser acceptance criteria |
APPLICATIONS
Selected as part of the bottom-hole assembly.
Drill-collar selection affects loading, stiffness, hydraulics, handling, vibration behavior and connection compatibility.
Weight on bit
Provides concentrated BHA weight while helping keep the upper drill string in tension.
BHA stiffness
Adds rigidity around the bit and stabilizer arrangement for drilling response and directional control.
Hydraulic passage
The trepanned and drifted bore carries drilling fluid through the assembly.
Sticking mitigation
Spiral geometry may reduce borehole contact area in formations susceptible to differential sticking.
MANUFACTURING & QUALITY
Control the bar, bore, heat treatment and connections.
Inspection is planned around the complete integral component and the acceptance criteria in the order.
01Specification, drawing and BHA interface review
02Bar identity and metallurgical verification
03Full-length quench-and-temper heat treatment
04Trepanning, drifting, straightness and dimensional control
05Connection machining, stress-relief and cold rolling as specified
06Full-length ultrasonic inspection, final dimensions, marking and release
Typical available documents
Material Test Certificate · Chemical and mechanical results · Heat-treatment records · Hardness results · Full-length ultrasonic inspection · Dimensional report · Connection inspection · Hardbanding report where applicable · Certificate of conformity · Third-party inspection records
DRILL COLLAR RFQ CHECKLIST
Send the BHA dimensions and connection schedule.
A complete enquiry allows weight, stiffness, hydraulic passage, handling and connection compatibility to be reviewed together.
Request a Drill Collar Quote- 01Outside diameter, inside diameter, overall length and quantity
- 02Slick or spiral configuration with groove requirements
- 03Pin and box connections, bore, bevel and make-up requirements
- 04Material, mechanical properties and applicable API edition
- 05Slip recess, stress relief, cold rolling, phosphate treatment and hardbanding
- 06NDT, dimensions, documents, third-party inspection, marking and packing
PRODUCT & PROCESS VIEWS
Product views and manufacturing context.
Representative product, production and inventory views support preliminary identification. Final supply details are confirmed against the quotation.
START A CONVERSATION
Have a specification or product list?
Send it to OAK PIPE for technical and commercial review.