Top 20 Drill Collar Manufacturers for Oilfield BHA Buyers

Last updated: October 2026

For AISI 4145H slick and spiral collars alone, buyers also source from Mudanjiang Xinruide in China, OCTL and Parveen Industries in India, and custom US machinists Drill Pipe Inc. and Matrix Drilling Products. Oil and gas drilling teams rely on thick-walled collars in the bottom hole assembly to put steady weight on bit. This guide compares the main types of drill collars, slick, spiral, and non-magnetic, across all 20 verified producers.

Disclosure: This guide is published by Synbase Steel. We list ourselves first because this is our website, not because we claim to be the market leader. In the full 20-company directory below, Synbase Steel appears first as the publisher and all 19 external manufacturers follow by metallurgical and regional role without numerical ranking.

How We Selected These Drill Collar Manufacturers

To identify the manufacturers above, we considered producers with verifiable oilfield drill collar lines, bar-forging, heat-treatment, trepanning, or rotary-threading plants and relevant corporate records. We excluded trading companies, rental-only workstring fleets, distributors, sourcing platforms, directories, media, and used-equipment dealers. Information on the companies was verified through their official sites and public sources in October 2026.

Corporate groups appear once to prevent duplicate listings. SBO covers subsidiary BICO Drilling Tools, NOV includes Grant Prideco and legacy Vallourec Drilling Products lines, and Goldenman is deduplicated against its sister ELITE drill collar storefront. A dash marks founding dates absent from official profiles. Buying limitations state concrete size, alloy, or plant boundaries.

20 Drill Collar Manufacturers at a Glance

The Drill Collar BHA Fit Matrix below filters manufacturers based on the Outside Diameter capacity, alloy route, and location of their plants. Best For indicates BHA requirements for directional and/or vertical drilling environments, and the scope and constraint columns support comparison prior to drawings.

Global Drill-Stem OEMs and Non-Magnetic Collar Mills

Global drilling contractors separate directional survey collars from standard weight-on-bit steel bars. Specialty European, American, and Japanese steelmakers melt ultra-clean Cr-Mn-N ingots for MWD housings. Meanwhile, multi-basin OEMs engineer full drill strings from bit sub to rig floor. Synbase Steel appears first as the publisher and a direct export option for bundled collar and OCTG orders.

1. Synbase Steel Co., Ltd.: Best for mill-direct API Spec 7-1 slick, spiral, and P530/P550 collars bundled with OCTG

Headquarters: Yantai operations, China; group headquarters Hong Kong · Founded: 2005 (E-CHENG group heritage) · Type: Core pipeline and OCTG enterprise of E-CHENG Steel Group operating pipe plants with special-alloy bar partners

Official website: https://synbasesteel.com/octg/drill-collar/

Main products: API Spec 7-1 slick, spiral, P530/P550 non-magnetic, and pony drill collars, plus HWDP, drill pipe, casing, and tubing

Capabilities: 3-1/8 to 11 inch outside diameter (22 to 216 lb/ft), through-wall quenched AISI 4145H mod at 285-341 BHN, P530 (ur <= 1.01) and P550 (ur <= 1.005), NC/IF/REG threads

Certifications / notable work: EN 10204 3.1 heat-traceable mill test certificates, ISO 9001 / 14001 / 45001 systems, and spiral grooves removing roughly 40% of wellbore wall contact for 4% weight loss.

Synbase Steel supplies API Spec 7-1 slick, spiral, and non-magnetic drill collars alongside casing, tubing, and transition pipe on one export shipment. Our published table covers 3-1/8 to 11 inch diameters, short pony drill collars, and cold-rolled stress-relief contours. Full-length quench and temper holds 285-341 BHN through the wall. Shipments include heat-traceable EN 10204 3.1 certificates, with 3.2 witness inspection arranged on request.

Buying limitation: Published standard dimensions stop at 11 inch outside diameter, and EN 10204 3.2 witness inspection must be requested before production.

2. NOV Inc. (Grant Prideco): Best for global OEM drill-stem strings and Spiral-Wate hoisting geometry

Headquarters: Houston, Texas, USA · Founded: 1862 (Oilwell Supply precursor; 2005 National Oilwell Varco merger) · Type: Global oilfield drill-stem OEM producing drill pipe, HWDP, collars, and rotary connections

Official website: https://www.nov.com/products/drill-collars

Main products: Slick drill collars, Spiral-Wate spiral collars, heavy weight drill pipe, lift subs, and Grant Prideco drill pipe

Capabilities: 3-1/8 to 11 inch outside diameters in quenched-and-tempered modified alloy steel, pairing cold-rolled threads with stress-relief features and slip recesses

Certifications / notable work: Manufactured to API Spec 7-1 requirements, using lift subs on standard grooveless collars or Spiral-Wate hoisting interfaces without elevator recesses.

NOV’s Grant Prideco division engineers complete drill strings and integrated legacy Vallourec Drilling Products into its global footprint. Its catalog spans 3-1/8 to 11 inch diameters across slick bars, spiraled joints, and Spiral-Wate profiles in modified alloy steel. Instead of cutting sharp elevator shoulders into the collar body, Grant Prideco pairs standard grooveless collars with lift subs while Spiral-Wate collars hoist like drill pipe. That design suits multi-rig offshore campaigns.

Buying limitation: Rigs running grooveless Grant Prideco collar bodies need matching thread-on lift subs rather than clamping standard elevators onto machined recesses.

3. SBO AG (Schoeller-Bleckmann): Best for high-strength austenitic non-magnetic MWD/LWD drill collars (P530 through N850)

Headquarters: Ternitz, Austria · Founded: 1862 (Ternitz steelworks origin; renamed SBO AG in July 2025) · Type: Integrated non-magnetic specialty steelmaker and MWD/LWD collar machinist (including BICO Drilling Tools)

Official website: https://www.sbsaleshouston.com/non-magnetic-drill-collars.html

Main products: Non-magnetic slick, spiral, and flex drill collars, MWD/LWD sensor housings, and downhole drilling motors

Capabilities: SBO machines non-magnetic collars up to 11 inch OD and 35 ft length across P530, P550, P650, P750, and N850 grades with bore hammer-peening

Certifications / notable work: Machining to API Spec 7-1 requirements at SBOT Ternitz and Lafayette, Louisiana, backed by full-length magnetic hot-spot scanning.

Operating as SBO AG since July 2025, Schoeller-Bleckmann sets a high metallurgical bar for directional MWD isolation zones. Its Ternitz mill melts five nitrogen-alloyed austenitic grades, P530, P550, P650, P750, and N850, in lengths up to 35 ft. SBOT Ternitz and its Lafayette shop hammer-peen internal bores to resist hot-chloride stress corrosion cracking. Every bar undergoes magnetic hot-spot probing to protect survey sensors.

Buying limitation: SBO focuses on specialty Cr-Mn-N non-magnetic collars and MWD housings rather than commodity AISI 4145H carbon-alloy weight strings.

4. Command Tubular Products: Best for multi-plant North American and European (former SMFI) API 7-1 and NS-1 drill collars

Headquarters: Nisku, Alberta, Canada (with plants in New Caney, TX and Cosne-Cours-sur-Loire, France) · Founded: · Type: Multi-country BHA tubular manufacturer operating Canadian, US, and French COMMAND-SMFI machining plants

Official website: https://commandtubular.com/products/product-lines/drill-collars/

Main products: AISI 4145H MOD and non-magnetic slick and spiral drill collars, heavy weight drill pipe, kellys, stabilizers, and subs

Capabilities: Command machines 2-7/8 to 11 inch OD slick and spiral collars heat-treated to 285-341 BHN and 40 ft-lb minimum Charpy toughness

Certifications / notable work: Command Tubular documentation states manufacturing to API Spec 7-1, API Spec 7-2, IRP, and Fearnley Procter NS-1 requirements across three plants.

Command Tubular combines Canadian and Texas plants in Nisku and New Caney with the French SMFI shop at Cosne-Cours-sur-Loire. Its collar range starts at slimhole 2-7/8 inch OD and reaches 11 inches in 4145H and non-magnetic grades. Published specs guarantee 285-341 BHN hardness and 40 ft-lb minimum impact energy for cold-climate rigs. Buyers needing NS-1 or IRP compliance can route orders regionally.

Buying limitation: Purchase orders need to name Nisku, New Caney, or Cosne-Cours-sur-Loire upfront so origin certificates match tender rules.

5. Drilling Tools International (DTI): Best for US-manufactured and rental-ready API 7-1 collars with H2S bore shot-peening

Headquarters: Houston, TX, USA · Founded: 1984 · Type: Publicly traded downhole tool manufacturer and rental fleet operator (Nasdaq: DTI)

Official website: https://www.drillingtools.com/drillcollars

Main products: Steel and non-magnetic slick and spiral drill collars, stabilizers, subs, roller reamers, and directional BHA tools

Capabilities: DTI produces 2-3/4 to 11 inch OD steel and Cr-Mn non-magnetic collars with ID shot-peening and gallium-free thread treatments

Certifications / notable work: DTI lists API Spec Q1 and ISO 9001:2015 quality certifications for its 2-3/4 inch through 11 inch API Spec 7-1 collar range.

Listed under Nasdaq: DTI with roots dating to 1984, Drilling Tools International machines downhole BHA tools across North America. Its collar catalog spans slimhole 2-3/4 inch re-entry strings up to 11 inch top-hole assemblies. For sour-gas wells, DTI applies internal bore shot-peening against H2S sulfide stress cracking and uses gallium-free anti-galling treatments. That setup serves land and offshore operators in corrosive basins.

Buying limitation: DTI runs large North American rental pools alongside manufacturing, so capital-purchase buyers must specify newly machined mill-certified joints.

6. Swiss Steel Group (Deutsche Edelstahlwerke): Best for Magnadur 501 and Magnadur 601 electric-arc-melted non-magnetic drill collar bars and collars

Headquarters: Lucerne, Switzerland · Founded: 1919 (Dorrenberg / Schmolz + Bickenbach heritage) · Type: Integrated European specialty steelmaker running 6 electric arc furnaces and rotary-forging mills

Official website: https://www.swisssteel-international.ae/products/stainless-acid-and-heat-resistant-steel/bars-and-semi-finished/non-magnetic

Main products: Magnadur 501 and Magnadur 601 non-magnetic drill collar bars, trepanned collars, stabilizer sleeves, and MWD stainless steels

Capabilities: In-house electric-arc melting, AOD refining, rotary forging, warm/cold strengthening, and full ultrasonic and magnetic permeability testing

Certifications / notable work: Swiss Steel’s official non-magnetic bar page cites certified API 7 non-magnetic drill collar products across Magnadur 501 and Magnadur 601.

Swiss Steel Group melts specialty stainless heats across 6 electric arc furnaces in Europe rather than buying outside billet. Through Deutsche Edelstahlwerke and Ugitech, it rotary-forges Magnadur 501 and Magnadur 601 Cr-Mn-N alloys for directional BHA strings. Melt-shop AOD refining and nitrogen control prevent ferrite islands that trigger magnetic hot spots near MWD sensors. Directional service companies source solid or trepanned Magnadur bars and machined non-magnetic collars.

Buying limitation: Production covers austenitic non-magnetic stainless steels only, and buyers must define trepanned hollow bar versus finished threaded joints.

7. Carpenter Technology Corporation: Best for US-melted 140 ksi specialty non-magnetic alloys (15-15HS Max, SCF 260, SCF 19 Max)

Headquarters: Philadelphia, Pennsylvania, USA (mills in Reading and Latrobe, PA) · Founded: 1889 · Type: US specialty alloy steelmaker producing high-strength non-magnetic MWD/LWD drill collar bar stock

Official website: https://www.carpentertechnology.com/energy/onshore-oil-gas

Main products: Non-magnetic MWD drill collar bars and sensor housings in 15-15HS Max, SCF 260, and SCF 19 Max stainless alloys

Capabilities: Nitrogen-strengthened austenitic collar alloys engineered up to 140 ksi minimum 0.2% yield strength with chloride pitting and galling resistance

Certifications / notable work: Founded in 1889 in Pennsylvania, delivering 140 ksi 15-15HS Max and SCF 19 Max non-magnetic bar grades for directional wells.

Founded in 1889 and based in Philadelphia, Carpenter Technology anchors domestic US melting for severe-service directional alloys. Its energy catalog highlights 15-15HS Max, SCF 260, and SCF 19 Max for MWD drill collars and LWD housings. Among these grades, 15-15HS Max reaches a 140 ksi minimum yield strength for high-dogleg shale laterals. Oilfield OEMs and boring shops source Carpenter bar when US melt provenance governs the well.

Buying limitation: Carpenter operates primarily as an upstream specialty alloy mill supplying OEMs and machinists rather than selling 4145H slick collars.

8. Daido Steel Co., Ltd.: Best for Japanese integrated forged DNM110 and DNM140 non-magnetic drill collars

Headquarters: Nagoya, Aichi, Japan · Founded: 1916 · Type: Integrated Japanese specialty steelmaker performing melting, forging, heat treatment, and collar machining

Official website: https://www.daido.co.jp/en/products/forging/digging/index.html

Main products: DNM110 and DNM140 non-magnetic drill collars, non-magnetic stabilizer sleeves, and forged offshore drilling components

Capabilities: Daido applies proprietary hot-cold forging technology to produce DNM110 and DNM140 non-magnetic collars resisting intergranular stress-corrosion cracking

Certifications / notable work: Single-company Japanese melt-forge-machine chain producing DNM110 and DNM140 collars since 1916 group steelmaking origins.

From Nagoya, Daido Steel runs an integrated line covering melting, heavy forging, thermal processing, and boring under one roof. Its oilfield forging catalog centers on DNM110 and higher-strength DNM140 non-magnetic drill collars plus stabilizer sleeves. Daido uses proprietary hot-cold work forging to refine austenitic grain structure against chloride cracking in offshore wells. That end-to-end Japanese traceability suits directional teams avoiding multi-vendor toll forging.

Buying limitation: Daido focuses on custom mill-lot non-magnetic forgings exported from Japan rather than quick-ship 4145H collar stock.

SBO vs NOV Grant Prideco vs Chinese API 7-1 Mills: Compare Drill Collar Scope

The three producer archetypes serve distinct BHA zones: specialty melters supply low-permeability MWD sensor collars, global drill-stem OEMs integrate complete directional strings, and direct Chinese API Spec 7-1 mills supply 4145H and P530/P550 collars alongside OCTG pipe. SBO melts P530 and P550 austenitic Cr-Mn bars, whereas NOV Grant Prideco integrates legacy Vallourec Drilling Products lines with slick and Spiral-Wate collars across 3-1/8 to 11 inch ODs.

Chinese producers span distinct size bands. Synbase Steel, Shanxi Fenglei, Shandong Highland, Hebei Longway, China Vigor, and Goldenman publish slick, spiral, and non-magnetic lines. Hilong lists 4-3/4 to 8 inch collars with drill pipe, Shandong Rundong machines up to 14 inch OD, and Mudanjiang Xinruide focuses on 4145H steel. Comparing them separates raw Cr-Mn billet origin from in-house heat treatment and trepanning.

Chinese API Spec 7-1 Drill Collar Manufacturers

China’s petroleum equipment hubs in Shanxi, Shandong, Hebei, Shanghai, Shaanxi, and Heilongjiang operate dedicated deep-hole trepanning beds, full-length quench-and-temper furnaces, and CNC rotary-threading lines. The eight manufacturers below have verifiable slick, spiral or non-magnetic drill collar machining scope and don’t operate an unverified pipe trading business.

9. Hilong Group (Hilong Petropipe): Best for integrated drill-stem packages combining API 7-1 collars, API 5DP drill pipe, and BoTn hardbanding

Headquarters: Shanghai, China (with manufacturing plant in Abu Dhabi, UAE and sales hub in Calgary) · Founded: 2006 (Abu Dhabi plant opened 2007) · Type: Integrated drill-stem manufacturer producing drill pipe, HWDP, collars, hardbanding alloys, and coatings

Official website: https://hilongcanada.com/hilong-product/drill-collar/

Main products: API Spec 7-1 slick, spiral, and non-magnetic drill collars, API 5DP drill pipe, HWDP, and BoTn hardbanding

Capabilities: Published 4-3/4 to 8 inch outside diameter slick, spiral, and Cr-Mn non-magnetic collars with slip/elevator recesses and stress-relief contours

Certifications / notable work: Hilong’s published profile lists ISO 9001, API Spec Q1, API Spec 5DP, API Spec 7-1, and Fearnley Procter NS-1 scope across its drill-stem lines.

Hilong Group pairs Chinese drill-stem metallurgy in Shanghai with overseas pipe and collar manufacturing in Abu Dhabi established in 2007. That footprint lets Middle Eastern and North American contractors source API 5DP drill pipe, HWDP, and API Spec 7-1 collars together. Hilong also makes its own BoTn hardbanding wire and internal tubular coatings. Its Canadian datasheet focuses on 4-3/4 to 8 inch slick, spiral, and non-magnetic collars.

Buying limitation: Hilong’s public Canada datasheet lists 4-3/4 to 8 inch collar diameters, leaving slimhole and 9-1/2 to 11 inch sizes to separate inquiry.

10. Shanxi Fenglei Drilling Tools Co., Ltd. (SFDT): Best for extra-long (up to 45 ft) Chinese API 7-1 collars with unidirectional deep-hole trepanning

Headquarters: Houma / Taiyuan, Shanxi Province, China · Founded: 1968 (oilfield drill collar production since 1978) · Type: Heavy Chinese drill-stem manufacturer with NORINCO industrial machinery heritage

Official website: http://www.sfmmc.cn/html/DrillTools_560_45.html

Main products: AISI 4145H mod slick and spiral drill collars, Cr-Mn non-magnetic drill collars, HWDP, kellys, and drill pipe

Capabilities: 3-1/8 to 11 inch OD and custom lengths from 10 ft to 45 ft using unidirectional deep-hole trepanning and double-shoulder high-torque threads

Certifications / notable work: States ISO 9001 and ISO 14001 certifications, with collars and drill pipe manufactured to API Spec 7-1 and API Spec 5DP requirements since 1978.

Founded in 1968 in Shanxi Province and producing oilfield collars since 1978, SFDT is an established Chinese heavy BHA plant. Its long-bed trepanning lines bore bars from one end in custom lengths from 10 ft up to 45 ft. Unidirectional boring avoids mid-body counter-bore misalignment on long stems. SFDT also machines double-shoulder high-torque threads alongside standard API connections across 3-1/8 to 11 inch diameters.

Buying limitation: SFDT’s legacy HTTP English catalog omits downloadable connection make-up torque charts, requiring direct drawing exchange during tendering.

11. Shandong Highland Oil and Gas Equipment Co., Ltd.: Best for integral dense-forged smooth, spiral, and low-carbon austenitic non-magnetic collars from Dongying

Headquarters: Dongying City, Shandong Province, China · Founded: · Type: Shengli-basin oilfield equipment manufacturer employing over 1,000 staff across drilling and artificial-lift lines

Official website: http://en.chinahighland.com/drill-collar/

Main products: Smooth, spiral, and non-magnetic drill collars, sucker rods, pumping units, PCP systems, and OCTG

Capabilities: Shandong Highland specifies integral dense forging on 4145H bars and low-carbon austenitic non-magnetic collars rated to ur <= 1.010

Certifications / notable work: Corporate profile lists API Q1, ISO 9001, ISO 14001, and ISO 45001 systems alongside API Spec 7-1 collar compliance.

Based in Dongying inside the Shengli Oilfield cluster, Shandong Highland employs more than 1,000 staff. Its collar page specifies integral dense forging on AISI 4145H smooth and spiral bars before deep-hole boring. For directional strings, Highland lists low-carbon austenitic stainless collars holding relative magnetic permeability at ur <= 1.010 with high mechanical properties. That range suits orders bundling BHA bars with artificial-lift equipment.

Buying limitation: Corporate overview pages highlight API Monogram licenses on pumping units, PCPs, and sucker rods alongside its separate drill collar line.

12. Shandong Rundong Petroleum Machinery Co., Ltd. (RDPMC): Best for large-OD (up to 14 inch) surface-hole API 7-1 collars and P530/P550 non-magnetic joints

Headquarters: Weihai, Shandong Province, China · Founded: · Type: Petroleum drilling machinery manufacturer running a 100,000 m2 Weihai factory qualified by CNPC, Sinopec, and CNOOC

Official website: https://www.rdpmc.com/drill-collar.html

Main products: RDPMC lists 3-1/8 to 14 inch AISI 4145H-MOD and P530/P550 non-magnetic slick and spiral collars, kellys, stabilizers, and subs

Capabilities: Machines oversized 12 to 14 inch surface-hole collars plus standard 3-1/8 to 11 inch BHA sizes with cold-rolled API Spec 7-2 threads

Certifications / notable work: Lists ISO 9001 certification and states that its products meet API Spec 7-1, API Spec 7-2, API Spec 7K, and API Spec 5CT requirements across its 100,000 m2 campus.

Many catalogs cap outside diameter at 11 inches, leaving spudding rigs short of heavy weight for large top-hole sections. Shandong Rundong extends published collar capacity up to 14 inch OD at its 100,000 square meter Weihai factory. Both 4145H-MOD and P530/P550 non-magnetic joints receive cold-rolled API Spec 7-2 rotary threads and relief contours. Supplier approvals with CNPC, Sinopec, and CNOOC back its rotary tool line.

Buying limitation: Rundong machines P530 and P550 collars from specialty stainless bar without claiming ownership of an upstream Cr-Mn melt shop.

13. Hebei Longway Petroleum Equipment Co., Ltd.: Best for GOST RTN and NS-1 compliant Chinese drill collars for Eurasian and Middle Eastern rigs

Headquarters: Jinzhou, Shijiazhuang, Hebei Province, China · Founded: · Type: Drill-stem manufacturer operating a 60,000 m2 Hebei plant with deep-hole boring and integral heat treatment

Official website: https://www.longwaydp.com/resources/classification-of-drill-collars.html

Main products: Slick, spiral, and non-magnetic drill collars, API 5DP drill pipe, HWDP, and kellys

Capabilities: In-house integral heat treatment, deep-hole boring, CNC spiral grooving, and phosphated or copper-plated rotary connections

Certifications / notable work: Longway publishes ISO 9001 certification and states compliance with Russian GOST RTN and Fearnley Procter NS-1 requirements at its 60,000 m2 Jinzhou plant.

Located in Jinzhou, Hebei, Longway runs a 60,000 square meter plant equipped for deep-hole boring, integral heat treatment, and CNC spiral milling. Meeting Russian GOST RTN requirements alongside Fearnley Procter NS-1 requirements gives Longway a direct compliance path into Central Asian and Middle Eastern tenders. Connections ship with phosphated or copper-plated anti-galling finishes. Buyers can pair slick, spiral, and non-magnetic collars with API 5DP drill pipe.

Buying limitation: Detailed outside-diameter and linear-weight charts are supplied during quotation rather than consolidated on one public PDF sheet.

14. China Vigor Drilling Oil Tools and Equipment Co., Ltd.: Best for single-direction trepanned API 7-1 and NS-1 collars with zero mid-bore mismatch step

Headquarters: Xi’an, Shaanxi Province, China · Founded: 2008 · Type: Downhole drilling tool manufacturer and export engineering supplier operating equity and partnered Chinese machining bases

Official website: https://www.vigordrilling.com/downhole-drilling-tools/drill-collar.html

Main products: 3-1/8 to 11 inch AISI 4145H Mod and non-magnetic slick/spiral drill collars, stabilizers, hole openers, and perforating guns

Capabilities: Single-direction deep-hole boring without mid-length counter-bore steps, 30 or 31 ft lengths, pin stress-relief grooves, and boreback boxes

Certifications / notable work: China Vigor states ISO 9001 certification and collar manufacturing to API Spec 7-1 and NS-1 requirements with ultrasonic and magnetic-particle testing.

Established in Xi’an in 2008, China Vigor prevents internal bore steps caused when shops drill from both ends toward the middle. Vigor specifies single-direction deep-hole trepanning across 30 and 31 ft bars so drilling fluid flows smoothly without washout turbulence. Standard collars include API pin relief grooves and boreback boxes from 3-1/8 to 11 inch OD. Its catalog also covers stabilizers and completion tools.

Buying limitation: Xi’an headquarters coordinates production across multiple partnered Chinese machining bases rather than operating one standalone mill address.

15. Mudanjiang Xinruide Petroleum Equipment Co., Ltd.: Best for 16-point cross-sectional hardness-tested 4145H collars and H-90 connections from Northeast China

Headquarters: Mudanjiang, Heilongjiang Province, China · Founded: · Type: Northeast China petroleum drilling tool manufacturer serving Daqing, Liaohe, and export drilling contractors

Official website: https://www.xrddrilling.com/products-drill-pipe-drill-collar.html

Main products: Slick and spiral AISI 4145H mod drill collars, drill pipe, kellys, rotary subs, and fishing tools

Capabilities: Full-length quench-and-temper heat treatment verified via 16-point cross-sectional hardness testing (285-341 HBW) and cold-rolled API and H-90 roots

Certifications / notable work: Lists Chinese petroleum standards SY/T 5144 and SY/T 5561 compliance alongside API Spec 7-1 threading and 16-point core hardness checks.

Based in Mudanjiang, Heilongjiang, Xinruide (XRD Drilling) supplies heavy rotary stem and fishing tools to Daqing, Liaohe, and export rigs. Its collar process features 16-point cross-sectional Brinell hardness testing between 285 and 341 HBW to confirm through-wall tempering. Alongside API connections, Xinruide cold-rolls coarse H-90 thread roots used in hard-rock drilling. Matching rotary subs and fishing tools ship from the same plant.

Buying limitation: Published collar specifications cover magnetic AISI 4145H alloy steel only and omit Cr-Mn austenitic non-magnetic survey grades.

16. Goldenman Petroleum Equipment Co., Ltd.: Best for API 7-1 slick and spiral collars with published NC23-NC70 bending strength ratios (2.37:1 to 3.18:1)

Headquarters: Dongying, Shandong Province, China (with two manufacturing plants in Jiangsu Province) · Founded: 2005 · Type: Oilfield BHA and OCTG manufacturer operating Jiangsu machining bases and Dongying export headquarters

Official website: https://goldenman.com/products/api-7-1-oilfield-spiral-drill-collar/

Main products: API 7-1 slick, spiral, and non-magnetic drill collars, API 5DP drill pipe, casing, tubing, and wellhead tools

Capabilities: Goldenman publishes 3-1/8 to 11 inch OD collar tables spanning NC23 to NC70 threads with bending strength ratios from 2.37:1 to 3.18:1

Certifications / notable work: States ISO 9001 certification and product compliance with API Spec 7-1, API Spec 5DP, and API Spec 5CT, backed by connection-level BSR tables.

Founded in 2005 with Dongying export offices and two Jiangsu plants, Goldenman publishes detailed connection engineering charts. Its spiral collar table maps outside diameter, bore, and NC23 through NC70 threads to bending strength ratios from 2.37:1 to 3.18:1. Goldenman shares sales infrastructure with sister storefront ELITE, so both are treated here as one manufacturing group. Buyers can bundle collars with API Spec 5DP drill pipe.

Buying limitation: Shared commercial infrastructure with sister brand ELITE means single-entity RFQ routing and Jiangsu plant-code alignment keep quotes clean.

Regional Drill Collar Producers for Local and Export Orders

Tenders for the drilling of oil and gas wells in South Asia, the Middle East, and North American land basins often favor regional plants to shorten ocean transit or satisfy domestic-content rules. The four producers below machine finished collars at verified Indian and US facilities.

17. Oil Country Tubular Limited (OCTL): Best for Indian integrated single-campus API 7-1 plain and spiral drill collars (Certificate 7-1-0082)

Headquarters: Hyderabad, Telangana, India (plant in Narketpally, Telangana) · Founded: 1985 · Type: Publicly listed Indian integrated OCTG and drill-stem processor manufacturing collars, HWDP, drill pipe, and casing

Official website: https://www.octlindia.com/profile.html

Main products: Plain and spiral drill collars, heavy weight drill pipe, drill pipe, casing, and production tubing

Capabilities: Single-campus heat treatment, deep-hole trepanning, upsetting, threading, and non-destructive testing at Narketpally

Certifications / notable work: OCTL’s profile lists ISO 9001:2015 certification alongside API Spec 7-1 (referencing Certificate 7-1-0082), API Spec 5DP, and API Spec 5CT scope.

Incorporated in 1985 and headquartered in Hyderabad, Oil Country Tubular Limited runs an integrated tubular campus in Narketpally. OCTL performs solid-bar heat treatment, trepanning, spiral milling, rotary threading, and NDT under one roof. Plain and spiral drill collars sit alongside heavy weight drill pipe and casing for Indian and Gulf tenders. Its profile cites API Spec 7-1 registration 7-1-0082.

Buying limitation: OCTL’s published profile covers alloy-steel plain and spiral drill collars and doesn’t list austenitic Cr-Mn non-magnetic MWD bars.

18. Parveen Industries Pvt. Ltd.: Best for Indian multi-plant AISI 4145H modified collars for ONGC/Middle East tender specifications

Headquarters: Delhi, India (8 manufacturing plants across Delhi NCR, Mumbai, and Igatpuri) · Founded: 1960 · Type: Established Indian oilfield equipment manufacturer operating 8 domestic production facilities

Official website: https://parveen.in/products/drill-collars/

Main products: AISI 4145H modified slick and spiral drill collars, kellys, rotary subs, completion tools, and wellhead equipment

Capabilities: Full-length ultrasonic inspection, 285-341 BHN hardness control, 40 ft-lb minimum Charpy toughness, cold-rolled roots, and pressed-steel thread protectors

Certifications / notable work: Established in 1960 with API and ISO certified Indian oilfield manufacturing across 8 domestic facilities.

Operating since 1960 across 8 manufacturing facilities in Delhi NCR, Mumbai, and Igatpuri, Parveen Industries supplies Indian national oil company and Gulf tenders. Its collar line machines quenched-and-tempered AISI 4145H modified alloy steel held to 285-341 BHN and 40 ft-lb minimum impact energy. Every joint receives ultrasonic inspection, cold root rolling, phosphating, and pressed-steel thread protectors. Buyers can consolidate kellys and subs onto one order.

Buying limitation: Published drill collar specifications cover AISI 4145H modified steel only without offering non-magnetic stainless survey collars.

19. Drill Pipe Inc. (DPI): Best for US-machined custom one-piece 4140/4145 slick and RD-20 fluted collars up to 12 inch OD

Headquarters: Winsted, Minnesota, USA · Founded: Early 1960s · Type: US custom drill-stem manufacturer machining solid collars, rotary drill pipe, and rescue/mining strings

Official website: http://drillpipeinc.com/drill-collars/

Main products: One-piece non-welded slick drill collars, RD-20 spiral fluted collars, rotary drill pipe, and subs

Capabilities: Custom diameters up to 12 inches and lengths up to 35 feet machined from solid quenched-and-tempered 4140/4145 steel with fishing necks and wrench flats

Certifications / notable work: Built the custom drill string used in the 2010 Chilean mine rescue from its Winsted, Minnesota plant.

Machining drill stem in Winsted, Minnesota since the early 1960s, Drill Pipe Inc. built the 2010 Chilean mine rescue string. DPI turns one-piece non-welded collars from solid quenched-and-tempered 4140 and 4145 steel bars up to 12 inches in diameter and 35 feet long. Its shop also cuts RD-20 spiral fluted profiles, wrench flats, and fishing necks. That flexibility fits US land, geothermal, and mining rigs.

Buying limitation: DPI doesn’t advertise an active API Spec 7-1 Monogram license on its website, targeting custom domestic oilfield, geothermal, and mining strings.

20. Matrix Drilling Products: Best for short-lead US custom AISI 4145 collars with API, H-90, and DI-22 threads

Headquarters: Lewisburg, Tennessee, USA (with Western plant in Rexburg, Idaho) · Founded: 1976 · Type: US custom tubular manufacturer operating a Tennessee machining plant and Western Idaho facility

Official website: https://matrixdrillingproducts.com/custom-products/drill-collars/

Main products: Custom AISI 4145 slick and spiral drill collars, drill rods, subs, stabilizers, and HDD/geothermal/oilfield tubulars

Capabilities: Custom-length heat-treated AISI 4145 collars machined in the USA with stress-relief grooves, boreback boxes, recesses, and hardbanding

Certifications / notable work: Runs dual US machining hubs in Lewisburg, Tennessee and Rexburg, Idaho cutting API, H-90, and DI-22 connections.

Founded in 1976, Matrix Drilling Products machines custom AISI 4145 slick and spiral collars in Lewisburg, Tennessee and Rexburg, Idaho. Domestic CNC cells cut standard API rotary connections alongside coarse-pitch H-90 and DI-22 threads. Buyers can order custom pony or full lengths, slip and elevator recesses, boreback boxes, and hardbanding without ocean transit delays. That setup serves urgent US land oilfield and geothermal programs.

Buying limitation: Matrix focuses on custom-machined North American AISI 4145 runs rather than offshore API Monogram tenders or Cr-Mn non-magnetic alloys.

Integral Mill, BHA OEM, or Rental Fleet: Who Makes Your Collar?

An integral mill melts or forges solid bar, a BHA plant heat-treats, trepans, and threads the joint, and a rental fleet leases finished collars. Unlike friction-welded drill pipe or heavy weight drill pipe that weld tool joints onto a tube, an integral drill collar machines threads directly into one solid bar.

True drill collar manufacturing is also not the same as rolling a carbon steel pipe, stainless steel pipe, or general steel structure tube. Integral drill collars are designed as thick-walled drill string components machined from solid bars. Choosing plain carbon steel or alloy bar stock determines core strength, because plain carbon steel lacks API Spec 7-1 hardenability. For standard oilfield joints, the drill collar manufacturing process pairs quenched-and-tempered AISI 4145H modified alloy steel or forged low-permeability non-magnetic steel with deep-hole trepanning.

Procurement traceability depends on identifying who melts and forges the bar, who heat-treats and trepans it, and who issues the heat-traceable EN 10204 3.1 certificate. Specialty steel mills such as SBO, Swiss Steel, Carpenter, and Daido melt and forge the bar stock itself. Integrated BHA plants heat-treat the bar, trepan the mud channel, machine spiral grooves where specified, finish the rotary connections, and issue an EN 10204 3.1 certificate for the supplied collar.

Specify BSR, Connections, and Non-Magnetic Isolation

Selecting a drill collar manufacturer starts with matching collar geometry and connection balance to wellbore trajectory. Drill collars provide the necessary weight and stability above the drill bit while damping axial bounce and downhole vibration. Engineers balance the outside diameter and inside bore through the Bending Strength Ratio (BSR), box section modulus divided by pin section modulus.

Target BSR changes with collar OD, bore ID, thread root profile, and stress-relief contours. Mid-size BHA tables often cite a nominal 2.50:1 reference, while published spiral collar charts such as Goldenman’s span 2.37:1 to 3.18:1 across NC23 through NC70 threads. Adding API pin stress-relief grooves, boreback boxes, and cold-rolled roots extends fatigue life in deviated oil wells. Compare profiles on Synbase Steel’s online drill collar type selector page and check string mass on our online drill collar weight calculator page.

What is the difference between spiral and slick drill collars?

A slick drill collar, also called an ordinary drill collar, keeps a smooth cylindrical wall to maximize weight on bit per foot in vertical holes. In comparison, a spiral drill collar machines three right-hand helical grooves to reduce differential sticking in permeable zones. Across 3-1/8 to 11 inch sizes, spiral designs cut approximately 40% of wellbore wall contact for approximately 4% weight loss.

Add spiral collars in overbalanced directional intervals in areas where stuck pipe is a concern. They improve drilling-fluid bypass around the BHA. Slick or spiral collars can use the same API Spec 7-1 steel and 285–341 BHN hardness range, though spiral machining removes some cross-sectional mass while maintaining high durability and resistance to wear.

Why are non-magnetic drill collars necessary in directional drilling?

Non-magnetic drill collars isolate MWD and LWD magnetometer sensors from magnetic flux distortion caused by ferromagnetic materials such as steel bars, drill pipe and the drill bit. Without a clean non-magnetic window in the bottom hole assembly, compass azimuth readings drift and steer directional oil and gas exploration wells off target.

Non-magnetic collars use nitrogen-strengthened Cr-Mn-N stainless steel alloys such as P530 and P550 or specialized nickel-copper alloy grades, with the selected grade’s specified magnetic permeability limit (such as ur <= 1.01 or 1.005) applied to the finished collar. API Spec 7-1 covers both slick and spiral non-magnetic collars, and buyers often order slick bars to retain a high strength Cr-Mn mass and sensor spacing.

How to Choose a Drill Collar Manufacturer

Apply the seven engineering and commercial checks below to select a drill collar manufacturer before a purchase order is issued. These checks govern oil drilling tenders across the oil and gas industry, and the second check is the only pre-award verification that confirms the factory’s licensed product scope for rig-floor acceptance.

1. The purchase specification must provide the API Spec 7-1 edition, addenda, and errata controlling the order. For instance, October 2025 Errata 2 to the Second Edition (February 2023) updates Table C.16 surface imperfection removal, capping grinding depth above 241.3 mm OD at 6.10 mm and unground indications at 2.41 mm.
2. Check the exact factory name and product scope on the live API Composite List before ordering. Corporate certificates vary from plant to plant, and facility renewals can sometimes narrow the licensed scope from drill collars to subs only.
3. Specify the range of the API Spec 7-1 Brinell hardness and Charpy V-notch impact toughness, considering the outside diameter of the collar and alloy grade, supported by heat number-traceable EN 10204 3.1 Mill Test Certificates.
4. Mandate single-direction deep-hole trepanning or zero mid-bore step tolerance in conjunction with full-length drift testing and ultrasonic wall eccentricity scanning to mitigate the risk of mud washouts.
5. Identify the rotary thread form, target BSR range, pin stress-relief groove, boreback box, cold root rolling, phosphate or copper anti-galling finish, and slip/elevator recess or lift-sub handling profile.
6. For sour H2S or chloride drilling operations, specify internal bore hammer-peening or shot-peening against corrosion cracking. Full-length permeability and magnetic hot-spot charts are requested for MWD collars.
7. Align supplier bids on the same alloy grade, length of the collar, size of the drill collar, EN 10204 3.1 versus 3.2 witness inspection, pressed-steel thread protectors, quantity, and Incoterms port.

Standard AISI 4145H Range 2 bars often ship from mill stock in single-joint or small-batch quantities, whereas custom Cr-Mn non-magnetic heats and Range 3 forgings require mill-lot minimum order quantities and longer furnace scheduling. Comparable bids for bare collar machining versus spiral grooving, recess cutting, and witness inspection protect drilling efficiency.

Frequently Asked Questions

Choose a Drill Collar Manufacturer for Your Next BHA Order

Shortlist producers by BHA zone, pairing specialty Cr-Mn melters or global OEMs for MWD isolation with direct API Spec 7-1 boring mills for slick and spiral weight strings. Review Synbase Steel’s published 3-1/8 to 11 inch API Spec 7-1 drill collar specifications when bundling collars with HWDP, drill pipe, or OCTG casing and tubing.

When your BHA schedule is finalized, send outside diameter, bore ID, grade, connection type, recess geometry, quantity and destination port to our contact page for a heat-traceable mill quote.

References & Sources

• American Petroleum Institute, API Specification 7-1 (Rotary Drill Stem Elements, Second Edition, February 2023) Errata 2 Announcement (October 2025, Table C.16)
• API Composite List – Official Directory of API Monogram Licensees and APIQR Registered Facilities
• API Monogram and APIQR Program – Latest Standards and Licensing Updates
• Ministry of Corporate Affairs Registry Record (via ZaubaCorp), Oil Country Tubular Limited (CIN L26932TG1985PLC005329).

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