Appearance
Standards do not dictate how to drill a hole — they define the language we use to specify what a good hole looks like, and the framework for proving that the process can deliver it consistently.
Overview
Deep hole drilling standards are organized in a clear hierarchy. Understanding each standard's scope and relationship to the others is essential for specifying processes, procuring equipment, and accepting work.
| Standard | Title | Scope | Latest Edition |
|---|---|---|---|
| VDI 3208 | Deep hole boring with gun drills | Gun drilling process, parameters, and quality | 2014-04 |
| VDI 3209-1 | Deep hole boring systems with external coolant supply | BTA and ejector drilling systems | 2024-01 |
| VDI 3209-2 | Skiving and roller burnishing | Finish machining of deep bored holes | 2019-01 |
| VDI 3210 | Deep-hole boring | Overview of methods and equipment | 2006-03 |
| VDI 3211 | Deep hole drilling on machining centers | Non-dedicated machine applications | 2015-01 |
| VDI 3212 | Acceptance test requirements for deep hole drilling machines | Machine geometric accuracy testing | 2014-07 |
| DIN 6535 | Cylindrical shanks made of hard materials | Carbide shank forms HA, HB, HE, HF | 2024-03 |
| ISO 286 | GPS — ISO code system for tolerances | IT grades for hole and shaft fits | 2010 |
The standards are published by the Verein Deutscher Ingenieure (VDI) in cooperation with DIN (Deutsches Institut für Normung) and are available through DIN Media in German and English.
VDI 3208 — Gun Drilling
VDI 3208 is the primary standard for gun drilling (single-lip deep hole drilling with internal coolant supply).
Scope
VDI 3208 covers the economical and productive operation of gun drilling for diameters typically in the range of 1–40 mm. It addresses:
- Tool design principles for single-lip gun drills
- Cutting geometry recommendations (inner angle, outer angle, point shift)
- Cutting data reference values for common material groups
- Coolant pressure and flow requirements
- Quality expectations (diameter tolerance, surface finish, straightness)
- Troubleshooting guidance for common gun drilling problems
Key Provisions
| Parameter | Recommendation |
|---|---|
| Cutting speed range | 20–160 m/min depending on material |
| Feed rate range | 0.008–0.080 mm/rev depending on diameter and material |
| Coolant pressure | 40–150 bar depending on diameter and depth |
| Coolant filtration | ≤ 20 µm (≤ 10 µm recommended for precision work) |
| Guide bush clearance | G6 tolerance, 0.003–0.008 mm clearance |
Application
VDI 3208 is the standard to reference when specifying gun drilling operations for new parts, establishing process parameters, or troubleshooting quality issues. It applies to both stationary tool (STS) and rotating tool (DTS) configurations.
VDI 3209-1 — BTA and Ejector Systems
VDI 3209-1 covers deep hole boring systems with external coolant supply — the BTA single-tube system and the ejector double-tube system.
Scope
The standard provides:
- System design principles for BTA and ejector tooling
- Cutting data reference values for solid boring, reaming, and core drilling
- Coolant quantity and pressure diagrams as functions of drilling diameter
- Machine drive power requirements for different diameters and materials
- Tool construction details for BTA drill heads and ejector systems
- Guidelines for coolant system design, including filtration and tank capacity
Coolant Pressure and Flow Diagrams
The most referenced elements of VDI 3209-1 are the coolant pressure and flow diagrams. These provide:
| Diameter (mm) | Recommended Flow (L/min) | Typical Pressure (bar) |
|---|---|---|
| 20 | 80–100 | 50–70 |
| 40 | 160–200 | 35–55 |
| 65 | 260–325 | 25–45 |
| 80 | 320–400 | 20–40 |
| 100 | 400–500 | 18–35 |
These values serve as baseline recommendations. Actual requirements depend on hole depth, material, and chip load.
VDI 3209-2 — Skiving and Roller Burnishing
Part 2 of VDI 3209 provides approximate values for skiving and roller burnishing operations performed on deep hole drilling machines. It covers:
- Material removal allowances for skiving
- Roller burnishing pressure and feed parameters
- Expected surface finish improvement (typical Ra reduction from 3–6 µm to 0.1–0.4 µm)
- Tool design for combination skive-and-burnish tools
VDI 3210 — Overview of Deep Hole Drilling Methods
VDI 3210 serves as an introductory standard that maps the landscape of deep hole drilling methods:
| Method Category | Included Processes | Typical Diameter Range |
|---|---|---|
| Single-lip drilling | Gun drilling (SLD) | 1–50 mm |
| Single-tube system | BTA / STS | 12–630 mm |
| Double-tube system | Ejector / DTS | 18–200 mm |
| Trepanning | BTA trepanning | > 100 mm |
| Counterboring | BTA counterboring | > 20 mm |
This standard is useful for process selection and for understanding the relationship between different methods. It includes application examples with selection criteria.
VDI 3211 — Deep Hole Drilling on Machining Centers
VDI 3211 addresses deep hole drilling performed on conventional machining centers rather than dedicated deep hole drilling machines.
Scope
The standard defines:
- Requirements for the machine tool (spindle, coolant system, feed axis)
- Tooling systems suitable for machining center applications
- Process limitations compared to dedicated machines
- Quality expectations when deep hole drilling on standard equipment
Critical Requirements
| Machine Feature | Minimum Requirement |
|---|---|
| Coolant pressure | ≥ 30 bar (40 bar recommended) |
| Coolant filtration | ≤ 30 µm |
| Spindle run-out (TIR) | ≤ 0.02 mm |
| Feed rate resolution | ≤ 0.001 mm/rev |
| Chip evacuation path | Unobstructed through spindle or coolant system |
VDI 3211 is particularly relevant for job shops and general engineering facilities that perform deep hole drilling as part of a larger machining sequence rather than as a dedicated operation.
VDI 3212 — Machine Acceptance Testing
VDI 3212 defines terms, procedures, and methods for testing the geometric accuracy of deep hole drilling machines with one or more spindles.
Scope
| Test Category | What Is Measured | Typical Limit |
|---|---|---|
| Spindle axis alignment | Coaxiality to guide bush axis | ≤ 0.02 mm |
| Guide bush bore | Roundness and diameter tolerance | H6 or better |
| Feed axis straightness | Deviation in X and Y planes | ≤ 0.01 mm/m |
| Spindle run-out (radial) | TIR at spindle nose | ≤ 0.01 mm |
| Spindle run-out (axial) | TIR under load | ≤ 0.005 mm |
| Coolant system | Pressure stability at operating point | ±5% of set point |
Acceptance Procedure
The standard specifies:
- Static tests — geometric measurements on the idle machine
- Dynamic tests — measurements under cutting conditions using test workpieces
- Thermal tests — measurement of thermal displacement during warm-up and steady-state operation
VDI 3212 compliance is typically specified when purchasing new machines or after major machine repairs.
DIN 6535 — Carbide Shank Forms
DIN 6535 standardizes cylindrical shanks made of hard materials (carbide, cermet, ceramics). It is the shank standard most relevant to deep hole drilling tooling.
Shank Forms
| Form | Description | Clamping System | Typical Tolerance |
|---|---|---|---|
| HA | Plain cylindrical shank | Hydraulic chuck, collet, shrink fit | h6 |
| HB | Cylindrical shank with side driving flat | Weldon-style side lock | h6 |
| HE | Cylindrical shank with inclined clamping surface | Whistle-notch side lock | h6 |
| HF | Plain shank with 90° cooling cone | MQL systems | h6 |
HA Plain Shank Dimensions (Selected)
| shank d (h6) mm | overall length L1 mm |
|---|---|
| 6 | 48 |
| 8 | 50 |
| 10 | 56 |
| 12 | 60 |
| 16 | 60 |
| 20 | 60 |
| 25 | 60 |
| 32 | 60 |
Selection Guidance
- HA (plain shank) — preferred for precision deep hole drilling where run-out must be minimized. Used with hydraulic or shrink-fit chucks.
- HB (Weldon flat) — used when high torque transmission is needed and some run-out is acceptable.
- HE (whistle notch) — combines axial retention with better concentricity than HB.
DIN 6535 HA is the default for gun drills
Gun drills and BTA tools are almost always supplied with DIN 6535 HA plain shanks. The h6 tolerance (tighter than the h8 used in DIN 1835 for steel shanks) is essential for maintaining the ≤ 0.02 mm concentricity requirement between the drill and the guide bush. Always specify HA shanks when ordering deep hole drilling tooling.
ISO 286 — Tolerance System
ISO 286 defines the ISO code system for tolerances on linear sizes, including the IT grade system used to specify bore diameters.
Relation to Deep Hole Drilling
| IT Grade | Typical Deep Hole Process | Application |
|---|---|---|
| IT7 | Gun drilling (best practice) | Precision hydraulic components, fuel systems |
| IT8 | Gun drilling or BTA (standard) | General engineering bores |
| IT9 | BTA or ejector drilling | Hydraulic cylinders, structural bores |
| IT10 | Ejector drilling or conventional | Non-critical clearance bores |
Tolerance Values (Selected Diameters)
| Dia. Range (mm) | IT7 (mm) | IT8 (mm) | IT9 (mm) | IT10 (mm) |
|---|---|---|---|---|
| 10–18 | 0.018 | 0.027 | 0.043 | 0.070 |
| 18–30 | 0.021 | 0.033 | 0.052 | 0.084 |
| 30–50 | 0.025 | 0.039 | 0.062 | 0.100 |
| 50–80 | 0.030 | 0.046 | 0.074 | 0.120 |
Hole Basis System
For deep hole drilling, specifications should use the hole basis system (capital letter H for the hole):
- H7 = minimum diameter equals nominal, tolerance band is positive
- H8 = wider tolerance, same zero point
- H9 = standard for hydraulic cylinder bores
Specifying "IT7" without a fit letter is ambiguous — always use "H7" to define both the width and position of the tolerance band.
Other Relevant Standards
DIN 51502 — Coolant Lubricants
DIN 51502 covers the classification and labeling of cooling lubricants. Relevant for deep hole drilling coolant selection, particularly regarding:
- Emulsion concentration testing methods
- Neat oil classification by viscosity and additive content
- Marking requirements for coolant containers
ISO 3685 — Tool Life Testing
ISO 3685 defines the standard for tool life testing with single-point turning tools. While not specific to deep hole drilling, it establishes the VB (flank wear width) measurement system used universally for gun drill wear assessment. A gun drill is typically reground when VB reaches 0.2–0.3 mm.
DIN EN ISO 4287 — Surface Finish
ISO 4287 defines surface texture parameters (Ra, Rz, Rmax) used in specifying deep hole bore quality. It establishes:
- Definition and calculation of Ra (arithmetic mean deviation)
- Definition and calculation of Rz (average maximum height)
- Measurement procedures and cut-off wavelength selection
DIN 8602 — Straightness Measurement
For deep hole drilling, straightness is often specified per DIN 8602 or equivalent standards that define measurement methods for bore axis deviation.
Standards Selection Guide
| Application | Primary Standard | Supporting Standards |
|---|---|---|
| Specifying a gun drilling process | VDI 3208 | ISO 286, DIN 6535 |
| Specifying a BTA drilling process | VDI 3209-1 | ISO 286, VDI 3212 |
| Specifying ejector drilling | VDI 3209-1 | VDI 3210 |
| Specifying skive and roller burnish | VDI 3209-2 | ISO 4287 |
| Procuring a deep hole drilling machine | VDI 3212 | VDI 3209-1 |
| Retrofitting a machining center | VDI 3211 | VDI 3208 |
| Selecting tool shanks | DIN 6535 | VDI 3208 |
| Specifying bore tolerance | ISO 286 | — |
| Measuring surface finish | ISO 4287 | — |
| Training new engineers | VDI 3210 (overview) | All others |
FAQ
What is the difference between VDI 3208 and VDI 3209?
VDI 3208 covers gun drilling (single-lip drilling with internal coolant supply through the tool). VDI 3209 covers BTA and ejector systems (external coolant supply with chip evacuation through the drill tube interior). The two standards address fundamentally different coolant and chip evacuation paths and are not interchangeable.
Which standard defines coolant pressure for BTA drilling?
VDI 3209-1 (Deep hole boring systems with external supply of coolant) defines coolant pressure and flow requirements for BTA and ejector drilling. The standard includes diagrams showing coolant quantity and pressure as functions of drilling diameter. The current edition is 2024-01.
Does DIN have a standard for gun drill dimensions?
There is no single DIN standard specifically titled "gun drill." Gun drill dimensions are defined by manufacturer-specific designs that conform to the shank interface standards (DIN 6535 for carbide shanks) and the process guidelines in VDI 3208. The cutting geometry (inner angle, outer angle, point shift) is not standardized — it is selected by the tool manufacturer based on the workpiece material.
What is VDI 3212 used for?
VDI 3212 defines acceptance test requirements for deep hole drilling machines. It specifies procedures for measuring geometric accuracy: spindle alignment to guide bush axis (≤ 0.02 mm), feed axis straightness (≤ 0.01 mm/m), spindle run-out, and coolant system pressure stability. VDI 3212 is referenced in machine purchase specifications and after major repairs.
How does ISO 286 apply to deep hole drilling tolerances?
ISO 286 defines the IT grade system. For deep hole drilling, specify H7, H8, or H9 hole basis tolerances rather than using IT grade alone. H7 is achievable with gun drilling under best practice; H8–H9 is standard for both gun drilling and BTA; H10 is typical for ejector drilling. The tolerance band widens with increasing diameter and depth ratio.
What is DIN 6535 HA and why is it important?
DIN 6535 HA defines a plain cylindrical carbide shank with h6 tolerance. It is the standard shank form for gun drills and BTA tools. The h6 tolerance (tighter than h8 used for steel shanks) is critical for maintaining concentricity between the tool and the guide bush within the required 0.02 mm alignment tolerance.
Which standard should I reference when buying a deep hole drilling machine?
Reference VDI 3212 (acceptance test requirements), VDI 3209-1 (coolant system requirements for BTA), and VDI 3208 (gun drilling parameters). The purchase specification should require compliance with VDI 3212 for geometric accuracy testing at installation, and the coolant system should meet the pressure/flow requirements in VDI 3209-1 for the intended diameter range.
Are these standards available in English?
Yes. VDI standards are published in both German and English through DIN Media (www.dinmedia.de). ISO standards are available through national standards bodies. DIN 6535 and related DIN standards are available with English translations through ANSI, DIN Media, and other national standards organizations.
Standards are periodically revised. Check with DIN Media or the relevant standards organization for the latest edition before specifying compliance. This article reflects industry knowledge as of 2026.