Appearance
Support equipment — steady rests, chip conveyors, and mist collectors — is often selected separately from the main machine. This leads to undersized components, compatibility problems, and performance bottlenecks. Integrate these systems at the machine specification stage, not after delivery.
Steady Rests
Purpose
Steady rests support long workpieces during deep hole drilling. A workpiece with a length-to-diameter ratio above 10:1 deflects under cutting forces without support, causing hole misalignment and diameter variation.
Steady Rest Types
| Type | Support Method | Best For |
|---|---|---|
| Manual steady rest | Operator-adjusted rollers | Low-volume, frequent changeovers |
| Hydraulic steady rest | Hydraulic clamping | Production runs, consistent setup |
| Self-centring steady rest | Simultaneous roller adjustment | High-precision round stock |
| Fixed steady rest | Fixed position, non-adjustable | Dedicated production, one part size |
Positioning Guidelines
| Workpiece Length | Number of Steady Rests | Placement |
|---|---|---|
| Up to 1 m | 0–1 | Near drill entry point if needed |
| 1–3 m | 1–2 | At mid-span and near drill entry |
| 3–6 m | 2–3 | Every 1.5–2 m |
| 6 m+ | 3+ | Every 1.5–2 m |
Steady Rest Roller Selection
| Roller Material | Best For | Limitations |
|---|---|---|
| Nylon / polyurethane | Finished surfaces, aluminium, brass | Low heat resistance |
| Steel with rubber coating | Steel bars, general purpose | Wears faster than hardened steel |
| Hardened steel | Rough bars, high feed forces | May mark finished surfaces |
| Ball-bearing rollers | High-speed rotation, low friction | Higher cost |
Tip: For deep hole drilling, position the first steady rest within 300 mm of the drill bushing. This prevents workpiece deflection at the drill entry point, where misalignment causes the most damage.
Chip Conveyors
Chip Volume in Deep Hole Drilling
Deep hole drilling produces 80–95% of removed material as chips. A 25 mm diameter hole drilled 1 m deep in steel removes approximately 3.9 kg of material. At production rates of 10–50 parts per hour, chip volumes reach 40–200 kg per hour.
Chip Conveyor Types
| Type | Chip Type Handled | Capacity | Best For |
|---|---|---|---|
| Hinge-belt conveyor | Broken chips, small curls | Medium | Gun drilling, fine chips |
| Scraper conveyor | Stringy chips, bird's nests | High | BTA drilling, steel |
| Magnetic conveyor | Ferrous chips only | Medium | Ferrous materials |
| Screw conveyor | Fine chips, wet chips | Medium | Limited space installations |
| Drag flight conveyor | Mixed chip types, heavy loads | Very high | Large BTA, high-volume production |
Conveyor Sizing
| Machine Type | Recommended Conveyor Width | Conveyor Speed Range |
|---|---|---|
| Small gun drill (up to 20 mm) | 150–250 mm | 1–3 m/min |
| Medium gun drill (20–40 mm) | 250–400 mm | 2–5 m/min |
| BTA drill (20–65 mm) | 400–600 mm | 3–6 m/min |
| Large BTA (65 mm+) | 600–900 mm | 3–8 m/min |
Integration Considerations
- Chip conveyor must extend under the full chip fall zone
- Conveyor discharge height must match chip bin or removal system
- Coolant return from conveyor must drain back to tank
- Access for conveyor maintenance (chain tension, sprocket wear)
- Safety interlocks: conveyor stop should trigger machine stop
Mist Collectors
Why Mist Collection Is Necessary
High-pressure coolant systems (50–200 bar) atomise coolant at the drill exit point, creating a fine mist. This mist:
- Reduces operator visibility
- Creates slippery floors
- Exposes operators to coolant aerosols (respiratory hazard)
- Settles on electrical components (short circuit risk)
Mist Collector Types
| Type | Efficiency (0.5–5 µm) | Maintenance | Best For |
|---|---|---|---|
| Media filter (panel) | 60–80% | Filter changes every 1–3 months | Light-duty, low mist volume |
| Cartridge filter | 85–95% | Element changes every 6–12 months | Most production machines |
| Electrostatic precipitator | 90–98% | Cell cleaning every 3–6 months | High mist volume, fine mist |
| HEPA + pre-filter | 99%+ | Pre-filter changes 1–3 months, HEPA annually | Enclosed machines, strict air quality |
Sizing Guidelines
| Machine Type | Recommended Airflow | Duct Diameter |
|---|---|---|
| Small gun drill, enclosed | 500–1,000 CFM | 150–200 mm |
| Medium gun drill, enclosed | 1,000–2,000 CFM | 200–300 mm |
| BTA machine, enclosed | 2,000–4,000 CFM | 300–400 mm |
| Open machine with mist canopy | 3,000–6,000 CFM | 400–500 mm |
Warning: Undersized mist collection is a common complaint in deep hole drilling shops. If the mist collector cannot keep the machine enclosure clear after 30 seconds of drilling, the airflow rating is too low. Oversize by 25–50% rather than undersize.
Integration Best Practices
| System | Design for Integration |
|---|---|
| Steady rests | Mounting locations on machine bed, hydraulic or pneumatic supply |
| Chip conveyor | Trench or pit below chip fall zone, coolant drain return |
| Mist collector | Duct routing from machine enclosure, electrical interlock with machine |
| All systems | PLC integration for status monitoring and alarms |
FAQ
How many steady rests do I need for a 4 m workpiece?
Two steady rests minimum — one at mid-span (approximately 2 m) and one near the drill entry point. For heavy cutting (BTA), add a third at the tailstock end.
Can I use the same chip conveyor for gun drilling and BTA?
Not recommended. Gun drilling produces broken, fine chips that behave differently from the long, stringy chips produced by BTA. A conveyor designed for one chip type will jam frequently with the other.
What mist collector efficiency do I need?
Minimum 85% efficiency for any indoor installation. Aim for 95%+ if operators work near the machine. Check local air quality regulations — some jurisdictions require 99%+ efficiency for coolant mist.
Should I buy support equipment from the machine manufacturer or third-party suppliers?
Machine manufacturer packages are guaranteed compatible but may cost 20–40% more. Third-party equipment offers better value if properly specified. Get the machine manufacturer's interface specifications before buying third-party.
How much floor space should I allocate for support equipment?
Plan for 30–50% additional floor space beyond the machine footprint. Chip conveyors extend beyond the machine bed, mist collectors need duct routing clearance, and steady rests require access space for setup changes.
Support equipment requirements vary by machine type, workpiece, and production volume. Consult equipment suppliers for specific sizing recommendations. This article reflects industry practice as of 2026.