A bar feeder or stock loader is the difference between a machine that runs unattended and one that needs an operator at every cycle. On a deep hole drilling machine, the feeder must not only load the workpiece but also align it precisely with the drill axis — a misaligned workpiece means a misaligned hole. Correct feeder setup and maintenance keep the machine running with minimal operator intervention.
Feeder Types
Bar Feeder Comparison
| Feeder Type | Loading Mechanism | Bar Capacity | Best For | Cycle Time |
|---|
| Magazine feeder (multi-bar) | Bars stored in magazine — loaded individually | 6–50 bars | Production runs — same diameter | 5–15 seconds per bar |
| Single-bar feeder | Operator loads one bar — machine feeds through | 1 bar at a time | Short runs — frequent diameter changes | 10–30 seconds |
| Automatic bar loader (telescoping) | Bar pulled from storage rack — fed into spindle | 10–100 bars | High-volume production | 5–10 seconds per bar |
| Pusher-type feeder | Hydraulic or pneumatic pusher advances bar | 1 bar at a time | Long bars — continuous feed | Continuous |
Stock Loader Comparison
| Loader Type | Motion | Workpiece Types | Typical Load Capacity | Cycle Time |
|---|
| Pick-and-place | 2-axis (X, Z) | Cut-to-length parts | 1–20 kg | 5–15 seconds |
| Gantry loader | 3-axis (X, Y, Z) | Long bars, tubes | 5–100 kg | 10–30 seconds |
| Robot (6-axis) | Full articulation | Any shape | 1–50 kg | 10–20 seconds |
| Gravity feeder | Tilt + slide | Small cylindrical parts | 0.1–5 kg | 2–5 seconds |
Selection Criteria
| Criterion | Bar Feeder Requirement | Stock Loader Requirement |
|---|
| Workpiece diameter | 3–150 mm (typical) | 5–200 mm |
| Workpiece length | 200–6000 mm | 50–2000 mm |
| Workpiece weight | Up to 500 kg | Up to 100 kg |
| Cycle time | < 15 seconds | < 20 seconds |
| Diameter range | Single diameter per setup | Variety possible |
| Changeover time | < 30 minutes (quick-change) | < 15 minutes (gripper change) |
| Automation level | Unattended operation | Unattended operation |
Feeder Sizing
| Machine Type | Typical Bar Diameter | Typical Bar Length | Recommended Feeder Type |
|---|
| Small gun drilling | 3–25 mm | 500–2000 mm | Magazine or single-bar |
| Medium gun drilling | 10–50 mm | 1000–4000 mm | Magazine or automatic |
| Large gun drilling | 20–100 mm | 2000–6000 mm | Automatic bar loader |
| BTA drilling (small) | 20–60 mm | 1000–3000 mm | Gantry or automatic |
| BTA drilling (large) | 50–200 mm | 2000–6000 mm | Gantry or robot |
Feeder Setup and Alignment
Initial Installation
| Step | Action | Detail |
|---|
| 1 | Position feeder relative to machine spindle | Aligned to spindle centerline |
| 2 | Level feeder | Feet adjusted — stable |
| 3 | Align feeder guide tube with spindle | Concentric within 0.1 mm |
| 4 | Secure feeder to floor | Anchor bolts |
| 5 | Connect electrical and control cables | Per wiring diagram |
| 6 | Connect air supply (if pneumatic) | Regulated per specification |
| 7 | Configure feeder control parameters | In CNC or feeder controller |
Alignment Procedure
| Step | Action | Detail |
|---|
| 1 | Mount alignment bar in spindle | Precision-ground bar — extends into feeder |
| 2 | Check alignment bar position relative to feeder guide tube | Measure gap — top, bottom, left, right |
| 3 | Adjust feeder position | Shims or adjustment bolts |
| 4 | Recheck alignment | Within 0.05 mm at spindle, 0.1 mm at feeder end |
| 5 | For long feeders — check sag | Support bar through full stroke |
| 6 | Tighten all adjustment locks | — |
| 7 | Remove alignment bar | — |
| 8 | Run test cycle with sample bar | Verify smooth feed |
Guide Tube Adjustment
| Parameter | Setting | Effect |
|---|
| Guide tube ID | 1–3 mm larger than bar OD | Too tight = binding — too loose = misalignment |
| Guide tube support spacing | 500–1000 mm | Prevents tube sag |
| Guide tube material | Steel with hardened bore or polymer liner | Wear resistance vs low friction |
| Lubrication (if needed) | Light oil on bar surface | Reduces feed force |
Workpiece Support
Support During Drilling
| Support Type | Location | Function | Adjustment |
|---|
| Steady rest (on feeder) | Near spindle entry | Supports bar at drilling position | Align to spindle center |
| Guide tube (full-length) | Within feeder | Supports bar along entire length | Fixed — sized to bar |
| Tailstock support (if equipped) | Far end of bar | Supports bar end | Align to spindle center |
| Chip guard / coolant seal | At spindle entry | Contains coolant and chips | Seal around bar |
Steady Rest on Feeder
| Step | Action | Detail |
|---|
| 1 | Position steady rest near spindle entry | Within 100 mm of collet/chuck |
| 2 | Open steady rest rollers | — |
| 3 | Insert bar through rest into spindle | — |
| 4 | Close rollers onto bar | Light contact — not tight |
| 5 | Check bar rotation | Should rotate freely |
| 6 | Adjust roller position | Centered on spindle axis |
| 7 | Lock steady rest position | — |
Routine Maintenance
Daily Checks
| Check | Action | Detail |
|---|
| Guide tube cleanliness | Wipe clean | Remove chips and debris |
| Feed mechanism | Observe cycle | Smooth operation — no hesitation |
| Bar surface condition | Visual | No scoring or damage from feeder |
| Coolant seals | Visual | No leaking at feeder end |
| Sensors | Clean | Chip buildup on sensors causes false readings |
Weekly Maintenance
| Task | Detail |
|---|
| Lubricate feed mechanism | Per manufacturer — slides, rollers, bearings |
| Check guide tube for wear | Measure ID — replace if worn oversize |
| Check steady rest roller condition | Wear, rotation, alignment |
| Clean chip area around feeder | Chips accumulation impedes operation |
| Check air filter / lubricator (pneumatic) | Drain water — fill lubricator |
Monthly Maintenance
| Task | Detail |
|---|
| Check alignment | Recheck feeder-to-spindle alignment |
| Inspect all fasteners | Tighten loose bolts |
| Check electrical connections | Loose connections cause intermittent faults |
| Check safety interlocks | Verify all guards and switches functioning |
| Lubricate all moving parts | Per manufacturer schedule |
Troubleshooting
| Problem | Possible Cause | Corrective Action |
|---|
| Bar does not feed | Guide tube dirty or damaged | Clean or replace guide tube |
| Feed mechanism jammed | Check pusher/ gripper mechanism |
| Bar diameter wrong | Verify bar diameter within feeder range |
| Air pressure low (pneumatic) | Check air supply — adjust regulator |
| Bar misaligned with spindle | Feeder misaligned | Realign feeder to spindle |
| Guide tube worn | Replace guide tube |
| Support bracket loose | Tighten support |
| Bar surface damaged by feeder | Guide tube has burrs or debris | Clean or repair guide tube |
| Feed gripper pressure too high | Adjust gripper pressure |
| Steady rest rollers too tight | Adjust roller clearance |
| Feeder jams | Chips in guide tube | Clean guide tube thoroughly |
| Bar has burrs on end | Deburr bar ends before loading |
| Wrong bar diameter | Check bar size |
| Feeder makes noise during operation | Dry slides or rollers | Lubricate |
| Guide tube misaligned | Realign |
| Steady rest rollers worn | Replace rollers |
Safety Considerations
| Safety Feature | Purpose | Requirement |
|---|
| Light curtain or interlock | Prevents access to moving parts while feeder operates | At feeder load area |
| Emergency stop | Immediate stop of feeder and machine | Within reach of feeder and machine |
| Pinch point guarding | Covers all pinch points on feeder | Fixed guards |
| Bar whip guard | Contains bar if it breaks or is ejected (long bars) | Full-length enclosure around bar |
| Safety PLC integration | Feeder stops on machine alarm and vice versa | Electrical interlock |
FAQ
How do I align a bar feeder with a deep hole drilling machine?
Mount a precision alignment bar in the machine spindle, extended into the feeder guide tube. Measure the gap between the bar and the guide tube at the spindle end and at the feeder end — adjust the feeder position (using shims or adjustment bolts) until the bar is concentric with the guide tube within 0.05 mm at the spindle end and 0.1 mm at the feeder end. Check along the full length of the guide tube for sag. Tighten all adjustment locks and verify with a test bar.
What type of bar feeder is best for deep hole drilling?
Magazine-type bar feeders are best for production runs of bars with the same diameter — they hold multiple bars and load automatically, enabling unattended operation. Single-bar feeders are adequate for short runs with frequent diameter changes. For very long bars (3–6 m), a pusher-type feeder with full-length guide tube support is required to prevent bar sag and maintain alignment. Match the feeder type to production volume and bar size.
Why does my bar feeder jam?
Common causes: chips or debris in the guide tube (clean thoroughly), bar ends not deburred (deburr before loading), bar diameter out of tolerance (verify within feeder range), guide tube worn or damaged (replace guide tube), feed gripper pressure incorrect (adjust per manufacturer), or alignment shifted (realign feeder to spindle). Intermittent jams are often caused by chip accumulation — regular cleaning prevents most jams.
How do I prevent bar surface damage from the feeder?
Ensure the guide tube is clean and free of burrs or debris. Use a polymer-lined guide tube for soft materials (aluminum, brass, titanium) to prevent marking. Adjust steady rest roller pressure — rollers should contact the bar lightly, not tightly. Lubricate the bar surface with a thin oil film if needed. Deburr bar ends before loading — a sharp burr can score the guide tube surface and then damage subsequent bars.
How often should a bar feeder be serviced?
Daily: clean guide tube, check feed mechanism operation, inspect bar surface for damage. Weekly: lubricate slides and rollers, check guide tube for wear, clean chip accumulation around feeder, check air filter/lubricator. Monthly: check feeder-to-spindle alignment, inspect fasteners and electrical connections, verify safety interlocks. Annually: full inspection including feed mechanism wear, guide tube replacement if needed, and control system check.
A bar feeder or stock loader is the key to unattended deep hole drilling operation. Correct alignment to the machine spindle is essential — a misaligned feeder causes jammed bars, damaged workpieces, and misaligned holes. Keep the guide tube clean, deburr bar ends, check alignment monthly, and perform routine lubrication. A well-maintained feeder runs reliably for years and keeps the machine producing. This article reflects industry practice as of 2026.
