Cannulated Bar Stock for Medical Applications: Titanium Grades, Dimension

 

Cannulated bar stock is a metal bar with a continuous axial bore, supplied as a machining blank for components that require an internal channel. In medical manufacturing, titanium cannulated bars are commonly used to produce orthopedic screws, fixation components, and guidewire-compatible surgical instruments.

For buyers, selecting cannulated bar stock involves more than choosing a titanium grade. OD, ID, wall thickness, bore alignment, straightness, surface condition, and traceability all affect whether the stock meets downstream machining requirements. This guide covers materials, manufacturing routes, critical dimensions, inspection evidence and supplier selection for medical cannulated titanium bar stock, with a focus on Ti-6Al-4V ELI (Grade 23) under ASTM F136. It is written as a technical selection and sourcing guide, not a general titanium primer.

What Is Cannulated Bar Stock?

Cannulated bar stock is round metal stock manufactured with a longitudinal hole running through its center, giving a ring-shaped cross-section with three basic dimensional characteristics:

• Outside diameter (OD): the overall diameter of the bar.
• Inside diameter (ID): the diameter of the axial bore.
• Wall thickness: the material thickness between the outer surface and the bore.

Unlike a finished medical component, cannulated bar stock is a semi-finished raw material. It is supplied in straight lengths and subsequently machined into components such as cannulated screws, fixation parts, and instrument shafts.

Cannulated Bar vs. Solid Bar vs. Hollow Titanium Tube

These product forms can overlap in name, but they differ in how the bore is formed and what must be controlled. Some suppliers use hollow bar, titanium hollow bar stock, cannulated bar, and thick-wall tube for related products, so compare the product standard, manufacturing route, dimensional drawing, wall thickness, bore characteristics and inspection records rather than the product name alone.

These descriptions represent different stock forms and bore-production routes rather than mutually exclusive product categories. A seamless hollow product, for example, may also be described as a hollow bar depending on its dimensions, applicable product standard, and intended machining use.

No form is automatically better suited to a component. The final component drawing, machining route, order quantity and required inspection evidence decide the choice. Cannulated bar stock is also a semi-finished raw material: a bar that meets a material specification does not establish that a finished screw, nail or instrument meets its own design and regulatory requirements.

Titanium Grades Used in Medical Cannulated Bar Stock

Material selection should follow the component drawing and applicable material specification. For implant-related applications, the grade, product form, material condition, and required documentation must all be confirmed before ordering.

Titanium Grade 23: Ti-6Al-4V ELI

Ti-6Al-4V ELI, commonly known as Grade 23, is the extra-low-interstitial version of Ti-6Al-4V specified for surgical implant applications under ASTM F136. The ELI designation reflects tighter control of interstitial elements such as oxygen, nitrogen, carbon, and hydrogen. ISO 5832-3:2021 also specifies wrought Ti-6Al-4V alloy for surgical implant applications. It notes that ELI material with more restrictive oxygen and iron limits may be ordered under the standard; however, the exact ELI composition requirements should be verified against the applicable specification, including ASTM F136 where required. These standards should not be treated as interchangeable unless the component drawing or responsible engineering authority explicitly permits it.

Mechanical requirements vary with product size, specimen orientation and material condition, so values should be read from the applicable table in the specified standard revision together with the test conditions, not quoted as one universal set. JH's article on Ti-6Al-4V ELI Grade 23 titanium covers the metallurgical background in more depth.

For cannulated bar procurement, buyers should verify:

• ASTM F136 compliance and the applicable standard revision.
• Grade 23 material designation.
• Chemical composition, including interstitial elements.
• Mechanical test results and test orientation.
• Material condition and product dimensions.
• Heat and lot traceability.

Titanium Grade 5: Ti-6Al-4V

Grade 5 and Grade 23 belong to the same general Ti-6Al-4V alloy family, but they are not interchangeable designations. ASTM B348 covers titanium and titanium alloy bars and billets, while ASTM F1472 covers wrought Ti-6Al-4V alloy for surgical implant applications. ASTM F136 specifies the ELI version for surgical implant applications. If a component drawing requires Grade 23 under ASTM F136, a supplier should not substitute general Grade 5 material without formal engineering approval.

Other Materials

Other materials may be used for cannulated medical products depending on the component specification, including commercially pure titanium under ASTM F67, Ti-6Al-7Nb under ASTM F1295 and implant-grade stainless steel under ASTM F138. Their suitability must be determined by the drawing rather than assumed from their use in other medical products.

How Is Cannulated Bar Stock Manufactured?

The manufacturing route determines how the axial bore is formed and what dimensional characteristics need to be controlled. Three common approaches are hollow forming or extrusion, drawing, and gun drilling. The routes below describe processes used in the wider titanium industry; they are not a statement that JH Medical Ti currently operates all of them. Ask any supplier which route applies to the specific product you are buying.

Hollow Forming and Extrusion

In this route, the hollow profile is created during forming or extrusion rather than drilled into a finished solid bar. Subsequent operations may reduce dimensions, improve surface condition and bring the bar closer to its final specification. Purchasing check: ask how the supplier controls bore geometry and wall uniformity over the full production length, and which dimensional records support it.

Drawing

Drawing reduces the dimensions of an existing hollow section by pulling the material through a die, often with a mandrel or plug to control the internal surface. It can improve dimensional consistency and may require intermediate heat treatment; it sizes an existing hollow form and does not create a bore in a solid bar. Purchasing check: ask how the mandrel or plug is controlled, which dimensional checks follow drawing, and whether intermediate heat treatment is required.

Gun Drilling and Deep-Hole Machining

Gun drilling creates an axial bore in a solid bar. It allows a selected OD to be paired with a specific ID, including custom combinations not available as standard hollow profiles. Bore quality depends on:

• Drill alignment and tool condition.
• Coolant delivery and chip evacuation.
• Tool deflection over the drilling length.
• Bore diameter and straightness.
• Internal surface condition.

The key question is whether the supplier can control and verify the bore characteristics required by the drawing. Purchasing check: ask about achievable drilling depth, ID tolerance, bore-axis deviation and how the internal surface is inspected.

Finishing and Inspection

After the primary forming or drilling process, additional operations may include straightening, centerless grinding, cutting to length, cleaning, and bore finishing where specified. The inspection plan should address both external and internal characteristics: a bar can have an acceptable outside diameter while still having an off-center or inconsistent bore.

No manufacturing route is automatically superior for every application. Selection should be based on the required geometry, production quantity, dimensional tolerances, surface requirements, and available inspection evidence.

Critical Dimensions and Technical Specifications

For medical cannulated bar stock, dimensional control affects material utilization, machining stability and downstream component quality. Five controls deserve particular attention:

• OD: nominal size and consistency along the length.
• ID: nominal bore size and consistency along the length.
• Wall thickness: minimum wall and circumferential uniformity.
• Bore alignment: deviation of the bore from the OD reference axis.
• Straightness: deviation of the whole bar over a defined length.

Each should be defined on the drawing or purchase specification, together with the measurement method and acceptance criterion.

Outside Diameter (OD)

OD determines the external size of the stock and its compatibility with the customer's machining equipment. For automatic machining operations, OD consistency can affect collet or guide-bushing fit, material feeding, and machining stability. Specify the nominal diameter, tolerance, surface condition, and measurement method. For longer bars, the inspection plan should also define where measurements are taken along the length.

Inside Diameter (ID)

ID defines the size of the internal channel. It may be designed to accommodate a guidewire, pin, instrument, or another specified component. The required ID depends on the downstream application. Buyers should state the nominal diameter, tolerance, and whether the bore must be checked at multiple positions along the bar. An ID measurement taken only at the two ends may not establish the condition of the entire bore.

Wall Thickness

Wall thickness is calculated from OD and ID:

Wall Thickness = (OD − ID) / 2

For example, a bar with an OD of 12 mm and an ID of 4 mm has a nominal wall thickness of 4 mm. This is a geometric calculation, not a guarantee that the actual wall is uniform around the circumference. If the bore is off-center, one side of the wall may be thinner than the other. For critical components, buyers should define a minimum-wall requirement and agree on how wall uniformity will be verified.

Bore Alignment, Eccentricity, and Total Indicator Runout (TIR)

Bore alignment describes the positional relationship between the internal bore and the outside diameter reference axis. Depending on the drawing and inspection standard, this relationship may be controlled through eccentricity, runout, or another agreed geometric tolerance. TIR is an indicator-based measurement obtained under a defined datum, support arrangement, and rotation setup. Because the reported value depends on the inspection method, buyers should agree on the datum, measurement position, acceptance criterion, and procedure before production.

Straightness and Dimensional Tolerances

Straightness describes how far a bar deviates from a defined straight reference over a specified length. It matters for long stock used in bar feeders and automated machining equipment, where excessive deviation can affect feeding, rotation, and machining consistency. OD and ID tolerances should be stated separately. The buyer should also specify cut length, end condition, and any required squareness.

Surface Finish and Internal Bore Quality

External surface finish and internal bore finish should be specified and inspected separately: a ground outside diameter does not establish the condition of the bore. Where internal surface quality is critical, define the required finish or defect criteria and agree on an inspection method. Depending on the geometry and specification, this may involve internal visual examination, borescope inspection, suitable gauges, or examination of sectioned samples. These are possible methods selected for the order, not a mandatory universal inspection sequence for every supplier.

A specification should describe the actual component requirement. Do not copy another supplier's catalogue values and assume they are automatically achievable or appropriate for a different product.

Medical Applications of Cannulated Titanium Bar Stock

Cannulated titanium bar stock is used as a starting material for components that require an axial channel. The main advantage is that the axial bore is already present when machining begins, potentially reducing or eliminating the need for a full-length deep-hole drilling operation during component manufacturing. JH's guide to medical titanium implant manufacturing shows where these blanks enter a downstream machining workflow.

Cannulated Bone Screws

Cannulated bone screws are placed over a guidewire through an internal channel. Starting with cannulated stock can reduce or eliminate the need to create the full axial bore from solid material. Depending on the component design, additional bore finishing or machining may still be required. Bore alignment and dimensional consistency therefore remain important supplier qualification criteria.

Orthopedic Fixation Components

Intramedullary, spinal and trauma fixation parts may use cannulated geometries. For longer components, straightness and bore alignment over the full length matter most; specify whether inspection covers selected locations or the full supplied length.

Spinal and Surgical Instrument Components

Instrument shafts, guide sleeves and guidewire-compatible parts may also use cannulated titanium stock. Grade, dimensions and condition follow the finished component design, and raw material compliance is not finished-device approval.

The Application and Raw Material Requirements table below summarizes the raw material considerations that differ by application, rather than restating the uses.

In every case the material is an input, not a finished device: design, machining, cleaning, verification and regulatory approval sit with the device manufacturer.

Quality Standards, Testing, and Traceability

A reliable cannulated bar specification should address three separate areas: material compliance, dimensional conformity, and supplier quality controls. These are documented separately, and one does not imply another.

Material Standards and Mill Test Certificates

For Grade 23 titanium cannulated bar stock, buyers commonly specify ASTM F136. The material certificate should identify the grade, applicable standard and revision, heat or lot number, material condition, chemical analysis, and required mechanical test results. Where ISO 5832-3 is specified by the customer, the supplier should confirm the exact requirements and documentation applicable to that order. Standards should not be treated as automatically interchangeable simply because they cover the same general alloy family.

JH's separate guide to solid medical titanium rod specifications covers ASTM standards, microstructure control and precision tolerances. This article stays focused on the bore-related dimensions, manufacturing routes and inspection evidence that are specific to cannulated stock.

Dimensional and Bore Inspection

In addition to material testing, the inspection plan should address the characteristics that distinguish cannulated stock from solid bar. Depending on the drawing, relevant checks may include:

• OD and ID measurements.
• Wall thickness or minimum-wall verification.
• Bore alignment, eccentricity or TIR.
• Straightness over the specified length.
• External and internal surface condition.
• Length and end condition.

The measurement method and acceptance criteria should be agreed before the purchase order is released. Bore inspection is highly method-dependent, and a report that states a value without describing the setup is difficult to reproduce.

Non-Destructive Testing and Traceability

Ultrasonic testing may be used to assess internal discontinuities in titanium products, subject to the product geometry, applicable procedure, and agreed acceptance criteria. It should not be assumed that every cannulated bar is automatically inspected using the same UT method or coverage. Buyers should confirm whether the inspection is performed on the actual delivered product and request the relevant records when required. Heat and lot traceability connects the delivered material to its manufacturing history, test results, and supporting documentation.

Finally, material certification and supplier quality-system certification do not constitute regulatory approval of the finished medical device. The device manufacturer remains responsible for its own design, verification, validation, and regulatory obligations.

How to Select a Cannulated Bar Stock Supplier

Supplier qualification should consider whether the manufacturer can provide the required material, maintain the specified dimensions, and document the delivered product. Before placing an order, evaluate the following:

• Material and standard compliance — confirm the exact grade, standard, revision, material condition, and required test documentation. For implant applications, do not accept a general statement such as "medical-grade titanium" as a substitute for the specified material designation.
• OD, ID, and wall thickness capability — provide the actual drawing and ask the supplier to confirm feasibility. Discuss tolerances, minimum wall requirements, and how dimensional consistency will be inspected.
• Bore manufacturing and inspection — ask whether the bore is formed, drawn, or drilled. Request details of the inspection method for ID, bore alignment, straightness, and internal surface condition.
• Production consistency and traceability — ask how the supplier manages batch identification, material certificates, inspection records, and nonconforming products. A sample inspection report from a comparable product can help assess the supplier's documentation.
• Delivery and customization — confirm available lengths, cut-to-length requirements, packaging, lead time, and minimum order quantity. For custom OD and ID combinations, provide the drawing early so the manufacturing route can be reviewed before quotation.

RFQ Checklist for Cannulated Titanium Bar

To obtain a technically comparable quotation, include:

• Material: Ti-6Al-4V ELI, Grade 23.
• Standard: ASTM F136, including the required revision.
• OD: nominal diameter and tolerance.
• ID: nominal bore diameter and tolerance.
• Wall thickness: nominal and minimum requirement.
• Bore alignment: eccentricity, runout or the agreed geometric tolerance, plus measurement method.
• Straightness: maximum deviation over the specified length.
• Length: supplied length and cut tolerance.
• Surface finish: external and internal requirements.
• Material condition: required heat treatment or delivery condition.
• Inspection: chemical, mechanical, dimensional, and agreed bore-related checks.
• Documentation: MTC, certificate of conformity, traceability, and inspection reports.
• Quantity: required lengths, order quantity, and packaging requirements.

Have a cannulated titanium bar drawing or material specification? Send it to JH Medical Ti for a technical review of the required grade, OD, ID, tolerances, length, and inspection requirements.

ASTM F136 Grade 23 Cannulated Titanium Bar from JH Medical Ti

JH Medical Ti, operated by Shaanxi Jinhan Rare Precious Metals Co., Ltd. in Baoji, Shaanxi, China, supplies medical titanium materials. The product relevant to this guide is its ASTM F136 Ti-6Al-4V ELI Grade 23 cannulated titanium bar; its team reviews a customer drawing to confirm material, dimensions and inspection requirements before quotation. Buyers can also review its JH Medical Ti manufacturing capabilities and wider medical titanium bar range. Published equipment information covering melting, forming, grinding and inspection is company-level information; the inspection items performed on a specific order must be agreed separately on the inspection documents.

JH publishes the following Grade 23 cannulated bar information:

These are published product-range references, not a blanket commitment. The published diameter range and wall-thickness range should not be read as a matrix in which every diameter can be combined with every wall thickness; the available OD/ID combinations and minimum wall must be confirmed for the order. A tolerance band such as h6–h9 applies to a stated dimension, machined condition and measurement condition, not to OD, ID, length and bore axis alike. No published ID range is stated, and data published for solid medical titanium bar cannot be transferred automatically to cannulated bar. Actual OD, ID, wall thickness, length, and tolerance combinations are subject to technical review and order-specific confirmation.

View the ASTM F136 Grade 23 cannulated titanium bar product page for published product details and enquiry options.

Frequently Asked Questions

What is cannulated bar stock used for?

Cannulated bar stock is used to manufacture components that require a longitudinal internal channel. Applications include cannulated bone screws, orthopedic fixation components, guidewire-compatible parts, and selected surgical instrument components.

What is the difference between cannulated bar stock and hollow titanium tubing?

Cannulated bar stock is generally supplied as a bar-form machining blank with an axial bore. Hollow titanium tubing is supplied as a tubular product and is commonly specified by OD and wall thickness. The actual difference depends on the product standard, manufacturing route, dimensions, and intended machining process.

Which titanium grade is used for medical cannulated bars?

Ti-6Al-4V ELI, Grade 23, under ASTM F136 is widely used for surgical implant material applications. Other titanium alloys may be used depending on the component design and specified material standard.

How is the bore made in a cannulated titanium bar?

The bore may be created during hollow forming or extrusion, followed by drawing and finishing. Alternatively, it may be produced by gun drilling or another deep-hole machining process in solid bar stock. The route affects bore characteristics and inspection requirements.

What specifications should I provide when ordering cannulated titanium bar stock?

At minimum, provide the material grade and standard, OD, ID, wall thickness, dimensional tolerances, bore alignment requirement, straightness, length, surface finish, material condition, inspection requirements, and required documentation.

Can cannulated titanium bar stock be customized?

Custom configurations may be possible depending on the supplier's manufacturing route, tooling, dimensions, and production capacity. Buyers should submit a drawing with OD, ID, wall thickness, length, and tolerance requirements for technical review before ordering.

What inspection documents should I request when buying medical cannulated titanium bar stock?

Buyers should request the material test certificate, chemical composition and mechanical test results, dimensional inspection records, and heat or lot traceability documents specified in the purchase order. Bore-related inspection records, such as ID, alignment, straightness, and internal surface checks, should also be agreed upon according to the component drawing and inspection plan.

Request a Quote for ASTM F136 Grade 23 Cannulated Titanium Bar

Send JH Medical Ti your drawing or RFQ, including the required material standard, OD, ID, tolerances, length, and inspection requirements. Our team can review the specification and confirm the applicable supply options.