Five-Axis Deep Hole Drilling
Deep hole drilling on 5-axis machines enables angled cooling passages, intersecting bores, and complex oil gallery geometries that cannot be produced on 3-axis machines. However, programming deep holes on 5-axis platforms introduces unique challenges — tool shank clearance at extreme angles, machine interference zones, and the need for precise tool axis control.
Applications
| Industry | Component | Hole Type | Why 5-Axis Needed |
|---|---|---|---|
| Aerospace | Landing gear fittings | Angled lubrication passages | Holes intersect at angles up to 30° |
| Oil & Gas | Valve bodies | Angled flow passages | Multiple ports at various angles |
| Automotive | Engine blocks | Angled oil galleries | Complex oil routing |
| Mold & Die | Injection molds | Conformal cooling channels | Follow contoured cavity surfaces |
| Medical | Implants | Angled fixation holes | Anatomical geometry |
Programming Strategies
3+2 Machining (Positional)
The most common approach for deep hole drilling on 5-axis machines: the tool axis is oriented to the required angle while the tool is not cutting, then drilling proceeds along that fixed axis.
Position the B/C axes → Lock → Drill → Retract → Reposition
Advantages:
- Same G83 peck cycles as 3-axis programming
- No synchronization issues
- Easier collision checking
- Standard post-processor output
Disadvantages:
- Slower for many holes at different angles
- Cannot drill curved holes
Full 5-Axis (Simultaneous)
The tool axis changes continuously during drilling. Rarely used for deep hole drilling due to:
| Issue | Risk |
|---|---|
| Tool clearance | Shank or holder may contact workpiece as axis changes |
| Chip evacuation | Changed axis changes chip flow direction |
| Surface finish | Varying axis produces varying pad contact |
| Programming complexity | Requires CAM output — manual programming impractical |
Recommendation: Use 3+2 for all deep hole drilling applications. Only use full 5-axis for special cases where the hole axis must follow a curved path.
B-Axis Head Strategies
B-Axis Considerations
| Machine Type | B-Axis Travel | Deep Hole Limitations |
|---|---|---|
| B-axis horizontal boring mill | ±90° | Long tools may contact machine enclosure at extreme angles |
| B-axis machining center | ±30–120° | Shorter travel; check head clearance at full extension |
| Table-type 5-axis (trunnion) | ±120° (table tilt) | Workpiece weight limits; chip evacuation against gravity at high tilt |
Programming B-Axis Deep Holes
Fanuc example — B-axis positioning:
1O0100 (5-AXIS DEEP HOLE - ANGLE HEAD)
2N100 B-30.0 (TILT B-AXIS TO -30°)
3N110 G00 X0 Y0 Z50.0 (POSITION)
4N120 M41 (COOLANT ON)
5N130 G00 Z5.0 (R-PLANE)
6N140 G83 Z-200.0 Q5.0 R1.0 P300 F0.018 (DRILL ALONG B-30° AXIS)
7N150 G80
8N160 G00 Z100.0
9N170 B0 (RETURN TO VERTICAL)
10N180 M30
Siemens PLANE Function
Siemens controllers provide the PLANE function for 5-axis programming:
1N100 TRANS X0 Y0 Z0 (WORK OFFSET)
2N110 PLANE SPATIAL SPA0 SPB-30 SPC0 (TILT TOOL AROUND B-AXIS)
3N120 T1 D1
4N130 G00 X0 Y0 Z50.0
5N140 M41
6N150 G00 Z5.0
7N160 CYCLE83(5.0, 0.0, 2.0, -200.0, 0, 5.0, 3.0, 0, 0.5, 1, 0)
8N170 G00 Z100.0
9N180 PLANE RESET (RETURN TO STANDARD PLANE)
10N190 M30
Collision Avoidance
Tool Shank Clearance
Long deep hole drills present significant collision risks in 5-axis operations:
| Risk | Cause | Check |
|---|---|---|
| Shank contact at B-axis | Tool rotates into workpiece at extension | CAM simulation at maximum tool extension |
| Holder contact | Tool holder hits part or fixture at angle | Visualize holder geometry |
| Tool tip deflection at angle | Off-axis loading on long tool | Reduce feed at angled entry |
| Machine head interference | Head casts shadow at extreme angles | Machine simulation |
Collision Checking Workflow
CAM software check:
- Import machine model (or use machine builder’s simulation)
- Set tool holder geometry accurately (not just tool diameter)
- Run collision detection with 0.5 mm clearance margin
Manual check (no CAM simulation):
- Mount a test bar of the same length as the deep hole drill (without carbide)
- Manually jog to the most extreme angle and extension
- Check clearance at all positions — minimum 5 mm from any obstruction
Machine simulation software:
- Use Vericut, NX CAM simulation, or Mastercam Sim
- Full machine model with heads, tables, and enclosures
- Test worst-case angles before running
Safe Angle Limits
| Tool L/D Ratio | Maximum Safe Tilt Angle (from perpendicular) | Notes |
|---|---|---|
| 10:1 | 15° | Gun drill will tolerate minor off-axis entry |
| 20:1 | 8° | Reduced angle — longer tool deflects more |
| 30:1 | 5° | Very limited off-axis capability |
| 50:1 | 3° | Essentially perpendicular only |
| 100:1 | 0° | Must be perpendicular — no off-axis tolerance |
CAM Simulation Requirements
| Requirement | Why It Matters for Deep Holes |
|---|---|
| Tool body model | Use actual shank diameter, not cutting diameter |
| Tool holder model | Must match actual holder (hydraulic chuck, collet, etc.) |
| Machine envelope | Full machine travel limits at all axes |
| Head interference | B-axis head shape matters at extreme angles |
| Clearance tolerance | Set to minimum 1 mm for deep hole tools |
| Overhang verification | Verify tool at maximum depth extension |
Programming Example: Angled Oil Gallery
Scenario: Ø8 mm × 250 mm at 20° from vertical in landing gear component
1O0800 (5-AXIS ANGLED DEEP HOLE)
2(LANDING GEAR OIL GALLERY)
3(Ø8 mm × 250 mm AT 20°)
4(300M STEEL)
5
6N100 G90 G80 G40 G49
7N110 G91 G28 Z0
8N120 T01 M06 (GUN DRILL)
9N130 G00 G90 X50.0 Y30.0 Z100.0 (CLEAR POSITION)
10
11; TILT B-AXIS 20° (3+2 POSITIONING)
12N140 B20.0
13N150 G43 H01 Z50.0
14N160 M41 (HIGH-PRESSURE COOLANT ON)
15
16; MOVE TO R-PLANE AT ANGLE
17N170 G00 Z5.0
18
19; DRILL AT 20° ANGLE
20N180 G83 Z-250.0 Q4.0 R1.0 P300 F0.015 S3000
21N190 G80
22
23; RETRACT AND RETURN
24N200 G00 Z100.0 (RETRACT ALONG TOOL AXIS FIRST)
25N210 M09
26N220 B0 (THEN RETURN B TO VERTICAL)
27N230 G91 G28 Z0
28N240 M30
Summary
Five-axis deep hole drilling is most practical using 3+2 positioning (position the tool axis, lock, drill) rather than simultaneous 5-axis. Collision avoidance is the primary concern — long drill shanks rotate into the workpiece at tilted B-axis positions. Tool L/D severely limits permissible tilt angles: 10:1 tools can tolerate up to 15°, while 100:1 tools must remain perpendicular. CAM simulation with accurate tool holder and machine models is essential for safe programming. For CAM programming of 5-axis deep holes, see CAM programming guide. For G-code program examples, see deep hole drilling G-code library.