Deep Hole Drilling Tooling
Deep hole drilling uses specialized tooling that differs fundamentally from conventional twist drills. Each method has its own tool system designed to solve the challenges of delivering coolant and evacuating chips at extreme depths.
This guide covers all major deep hole drilling tool types — gun drills, BTA heads, DTS heads, trepanning tools, and their supporting components — organized by method.
Tool Types by Method
Gun Drilling Tools
Gun drills use a single-lip cutting tool with an integral coolant channel and external V-flute for chip evacuation.
Three main configurations:
| Type | Diameter | Regrinds | Best For |
|---|---|---|---|
| Solid carbide | 0.5–12 mm | 7–10 | Maximum rigidity, small diameters |
| Brazed tip | 1–30 mm | 3–5 | General-purpose, best value |
| Indexable insert | 16–50 mm | None (index) | Large diameters, no regrinding |
Key features:
- Single carbide cutting tip (one-lip design)
- Internal coolant hole from shank to tip
- V-shaped external flute for chip evacuation
- Carbide guide pads behind the cutting edge
For detailed coverage, see our gun drill geometry guide.
BTA Drilling Tools
BTA uses a modular system: a drill head carrying multiple cutting edges, threaded onto a thick-walled drill tube.
Drill head types:
| Type | Diameter | Edge Replacement | Best For |
|---|---|---|---|
| Brazed carbide head | 7.76–65 mm | Regrind (3–5×) | Precision, smaller diameters |
| Indexable insert head | 15–300+ mm | Index inserts | Large diameters, high volume |
The drill tube is a heavy-walled steel tube that carries coolant forward (through the annulus between tube and bore wall) and evacuates chips back (through the hollow center). A tube can last through hundreds of head changes.
For detailed coverage, see our BTA drilling tools guide.
Ejector (DTS) Drilling Tools
Ejector drilling uses a double-tube boring bar with a Venturi-effect drill head.
| Component | Function |
|---|---|
| DTS drill head | Cutting inserts + Venturi slots + guide pads |
| Inner tube | Chip evacuation path (suction) |
| Outer tube | Coolant delivery path |
| Coolant swivel | Transfers coolant to rotating bar |
The DTS head combines cutting edges, guide pads, and Venturi nozzles in one assembly. The Venturi slots are the most critical feature — they create the suction that evacuates chips.
For detailed coverage, see our ejector drilling tools guide.
Trepanning Tools
Trepanning heads cut an annular ring around a central core. The head has a hollow center through which the core passes.
| Feature | Description |
|---|---|
| Outer cutting inserts | Cut the finished bore diameter |
| Inner cutting inserts | Cut the core outer diameter |
| Core passage | Hollow center for core to pass through |
| Core breaker | Severs the core at full depth |
Trepanning heads are typically used at diameters above 50 mm where the core has salvage value.
Tool Materials
Carbide Grades
The vast majority of deep hole drilling tools use tungsten carbide (WC-Co) cutting edges.
| Application | Carbide Grade | Cobalt % | Grain Size |
|---|---|---|---|
| General steel | ISO K20–K30 | 6–8% | Medium (1–2 µm) |
| Stainless steel | ISO K35–K40 | 8–12% | Fine (0.5–1 µm) |
| Hardened steel | ISO K15–K20 | 4–6% | Fine |
| Aluminum / non-ferrous | ISO K10–K15 | 3–5% | Coarse (2–5 µm) |
| Cast iron | ISO K20–K30 | 6–8% | Medium |
Coatings
Coatings extend tool life 2–5× compared to uncoated carbide:
| Coating | Best For | Max Temp |
|---|---|---|
| TiAlN | General steel, stainless | 800–900°C |
| AlTiN nano | Hardened steel, superalloys | 900–1,100°C |
| CVD diamond | High-Si aluminum, composites | 600°C (non-ferrous) |
| DLC | Aluminum, adhesive materials | 400°C |
| Uncoated | Aluminum, brass, light cuts | N/A |
For detailed coating selection, see our gun drill coatings guide.
Guide Bushings
Guide bushings support the tool at the workpiece entry point. They are consumable wear items.
| Bushing Type | Material | Life | Best For |
|---|---|---|---|
| Carbide bushing | Tungsten carbide | 2,000–10,000 holes | High-volume production |
| Hardened steel | Tool steel (HRC 60+) | 500–2,000 holes | General production |
| Bronze | Phosphor bronze | 100–500 holes | Prototyping, soft materials |
| Polymer | Engineered plastic | 50–200 holes | Sealing applications, whip guides |
Bushing specifications:
- ID tolerance: gun drill diameter + 0.005–0.013 mm
- Alignment: < 0.01 mm TIR to spindle axis
- Replace when ID wear exceeds 0.025 mm
Coolant System Components
Every deep hole drilling system requires a coolant subsystem with these components:
| Component | Function | Key Spec |
|---|---|---|
| High-pressure pump | Deliver coolant at required pressure | Pressure and flow by method |
| Filter system | Remove chips and fines | 10–20 micron (production) |
| Chip separator | Separate chips from return coolant | Required for BTA and DTS |
| Coolant chiller | Maintain coolant temperature | 30–40°C target |
| Coolant swivel | Transfer coolant to rotating tool | Pressure-rated to system max |
| Hoses and fittings | Connect components | Rated to 1.5× system pressure |
For equipment selection, see our deep hole drilling equipment guide.
Workholding
| Workholding Type | Best For | Key Consideration |
|---|---|---|
| Standard chuck / collet | General gun drilling | Sufficient clamping force |
| Hydraulic steady rest | Long shafts (BTA) | Supports workpiece at multiple points |
| Pressure head (BOZA) | BTA drilling | Seals coolant at entry |
| Custom fixture | Irregular parts | Must allow tool pass-through |
| Faceplate | Large, heavy parts | For dedicated BTA machines |
Tool Life Comparison
| Tool Type | Holes Between Regrinds | Total Service Life |
|---|---|---|
| Gun drill (brazed) | 300–800 holes | 1,200–4,000 holes (3–5 regrinds) |
| Gun drill (solid carbide) | 500–1,500 holes | 4,000–15,000 holes (7–10 regrinds) |
| BTA head (brazed) | 200–500 holes | 600–2,500 holes (3–5 regrinds) |
| BTA insert | 100–500 per edge | 400–3,000 per insert (4–6 edges) |
| DTS insert | 100–500 per edge | 400–3,000 per insert (4–6 edges) |
| Guide bushing (carbide) | 2,000–10,000 holes | Replace when worn |
Summary
Deep hole drilling tooling is specific to each method: gun drills for small diameters and precision, BTA modular heads and tubes for high-production medium-to-large holes, DTS double-tube systems for CNC machine retrofits, and trepanning heads for material-saving annular cuts. Tool material is almost always tungsten carbide, with coatings (TiAlN, AlTiN, DLC, CVD diamond) selected based on workpiece material. Guide bushings, coolant system components, and workholding complete the tooling system for each method.
For method-specific tooling details, see the individual cluster guides linked above. For tool wear and regrinding, see deep hole drilling tool wear analysis. For a complete overview, visit the tools and equipment guide.