In deep hole drilling, chips are produced continuously — a single deep hole can generate kilograms of chips. The chip conveyor is the system that removes these chips from the machine area. A conveyor jam stops production; a properly selected conveyor runs unnoticed.
Chip Characteristics by Drilling Method
Chip Type Comparison
| Drilling Method | Chip Form | Chip Size | Chip Shape | Chip Volume |
|---|
| Gun drilling (steel) | Continuous ribbon | 0.5–2 mm wide, up to several meters long | Long, stringy, spiral ribbon | 5–30 cm³ per cm of hole |
| Gun drilling (aluminum) | Continuous ribbon | Similar — may be finer | Long ribbon, fine dust | 3–15 cm³ per cm of hole |
| Gun drilling (cast iron) | Broken chips | 0.2–1 mm particles | Fine, powdery | Variable |
| BTA drilling (steel) | Small broken chips | 2–10 mm | C-shaped, comma-shaped | 10–50 cm³ per cm of hole |
| BTA drilling (aluminum) | Small broken chips | 3–15 mm | Irregular, segmented | Similar volume |
| STS / ejector drilling | Small broken chips | 2–8 mm | Similar to BTA | Similar to BTA |
Chip Handling Difficulty
| Chip Type | Difficult | Why | Better Conveyor Type |
|---|
| Long ribbon chips (gun drilling, steel) | Very | Tangles, wraps around conveyor components, bridges across openings | Scraper with bar grating or hinge belt with high back |
| Small broken chips (BTA, steel) | Low | Free-flowing, no tangling | Hinge belt or scraper |
| Fine chips (cast iron, aluminum) | Moderate | Can pack, create sludge when wet | Magnetic (for ferrous) or scraper |
| Mixed chips (steel + coolant) | Moderate | Coolant makes chips sticky, corrosion | Hinge belt with drainage |
Conveyor Types
Hinge Belt Conveyor
| Characteristic | Description |
|---|
| Mechanism | Interlocking steel or plastic belts driven by sprockets — chips carried on top of belt |
| Chip types | Small to medium broken chips — best for BTA chips |
| Capacity | 50–500 kg/hour typical |
| Advantages | Simple design, low maintenance, good coolant drainage |
| Disadvantages | Not suitable for long stringy chips — tangles in belt links |
| Typical application | BTA drilling, STS drilling — small broken chips |
Scraper / Drag Chain Conveyor
| Characteristic | Description |
|---|
| Mechanism | Chains with scraper bars pull chips along a trough — chips dragged, not carried |
| Chip types | All types — suitable for long stringy gun drilling chips |
| Capacity | 100–2,000 kg/hour |
| Advantages | Handles long chips that would tangle hinge belts, durable, self-cleaning |
| Disadvantages | Higher maintenance (chain wear), higher power consumption, more expensive |
| Typical application | Gun drilling — long ribbon chips, heavy-duty applications |
Magnetic Conveyor
| Characteristic | Description |
|---|
| Mechanism | Series of moving magnets under a stationary plate — ferrous chips attracted and moved |
| Chip types | Ferrous only (steel, cast iron) — small chips and fines |
| Capacity | 20–200 kg/hour for fine chips |
| Advantages | No mechanical belt — fewer jams, removes ferrous fines from coolant, compact |
| Disadvantages | Non-ferrous chips pass through, limited capacity, magnets lose strength over time |
| Typical application | Cast iron machining, secondary ferrous chip collection |
Screw / Auger Conveyor
| Characteristic | Description |
|---|
| Mechanism | Rotating screw inside a tube or trough moves chips axially |
| Chip types | Small broken chips, granular material |
| Capacity | 20–300 kg/hour |
| Advantages | Compact, fully enclosed (contains coolant), low cost, simple |
| Disadvantages | Will jam with long stringy chips, limited length (typically < 6 m), wear on screw and trough |
| Typical application | Collecting chips from multiple machine outlets into a central system |
Selection Criteria
Selection Matrix
| Primary Chip Type | Recommended Conveyor Type | Secondary Option | Not Recommended |
|---|
| Long ribbon (gun drilling — steel) | Scraper / drag chain | — | Hinge belt, screw, magnetic |
| Small broken (BTA — steel) | Hinge belt | Scraper | Screw (low volume only), magnetic |
| Fine ferrous (cast iron) | Magnetic | Scraper | Hinge belt (fines fall through) |
| Fine non-ferrous (aluminum) | Scraper | Hinge belt | Magnetic |
| Mixed chips (BTA + fines) | Hinge belt with fines pan | Scraper | Screw, magnetic |
Capacity Sizing
| Parameter | Formula / Guideline | Example |
|---|
| Chip volume per hole | Hole cross-section area × depth (theoretical) + 50% (swell factor) | 50 mm dia × 1 m deep = 1,960 cm³ × 1.5 = 2,940 cm³ |
| Chip weight per hole | Volume × material density (steel ≈ 7.8 g/cm³, but chips are ~30% solid) | 2,940 × 0.3 × 7.8 = 6.9 kg |
| Hourly chip load | Chips per hole × parts per hour | 6.9 kg × 5 parts/hour = 34.5 kg/hour |
| Conveyor capacity | 2× hourly chip load (minimum) | 70 kg/hour minimum |
Installation Considerations
Conveyor Location
| Configuration | Description | Best For |
|---|
| Under-machine (inline) | Conveyor directly below spindle/table | Gun drilling machines — chips fall directly into trough |
| Side discharge | Chips pushed or washed to side conveyor | BTA machines — chips exit with coolant |
| Central system | Multiple machines feed one conveyor | High-volume production — central chip processing |
| Pit-mounted | Conveyor installed in floor pit | Machines with limited overhead clearance |
Coolant Return
| Feature | Purpose | Design Consideration |
|---|
| Perforated belt / slotted trough | Separates coolant from chips | Drainage area: minimum 40% of belt area |
| Coolant return pan | Collects coolant drained from chips | Tilt toward tank, minimum 5° slope |
| Chip wiper / squeegee | Removes coolant from belt return | Reduces coolant carryover to chip bin |
Common Conveyor Problems
| Problem | Likely Cause | Corrective Action |
|---|
| Belt jams (hinge belt) | Long chips tangling in belt links | Switch to scraper conveyor, improve chip breaking |
| Chain jams (scraper) | Overload, worn chain, foreign object | Clear jam, inspect chain, check for wear |
| Sprocket skipping | Worn sprocket or chain | Replace sprocket and chain as set |
| Belt tracking off | Misaligned sprockets, tension uneven | Realign sprockets, adjust tension |
| Fines passing through belt | Perforation too large | Reduce perforation size, add fines pan |
| Conveyor motor overload | Chip jam, bearing failure, belt too tight | Clear jam, replace bearings, adjust tension |
| Coolant carryover to chip bin | Wiper worn, belt drainage inadequate | Replace wiper, improve drainage |
Maintenance Requirements
Daily Maintenance
| Task | Reason |
|---|
| Check for jams or material buildup | Prevents overload and motor damage |
| Verify belt/chain movement | Detect developing problems |
| Check coolant drainage | Confirm effective separation |
| Remove any long chips that may tangle | Prevent progressive clogging |
Weekly Maintenance
| Task | Reason |
|---|
| Inspect belt or chain tension | Prevents tracking issues and wear |
| Check sprocket condition and alignment | Extends chain/belt life |
| Lubricate bearings per manufacturer | Prevents bearing failure |
| Clean wiper / squeegee | Ensures effective coolant removal |
Monthly Maintenance
| Task | Reason |
|---|
| Inspect belt for wear or damage | Replace before failure |
| Check chain stretch and pins | Replace worn chain before it breaks |
| Inspect trough for wear | Especially scraper conveyor troughs |
| Check motor and gearbox condition | Verify oil level, listen for noise |
FAQ
What type of chip conveyor is best for gun drilling?
Scraper (drag chain) conveyors are best for gun drilling because gun drilling produces long, stringy ribbon chips. These chips would tangle in hinge belt links and jam screw conveyors. Scraper conveyors drag the chips along a trough without the need for chips to pass through belt openings — avoiding the entanglement problem that other conveyor types experience with long chips.
What type of chip conveyor is best for BTA drilling?
Hinge belt conveyors are best for BTA drilling because BTA drilling produces small, broken chips (C-shaped or comma-shaped) that do not tangle. Hinge belt conveyors are simpler, lower cost, and lower maintenance than scraper conveyors. The belt openings provide effective coolant drainage. For large BTA applications (> 80 mm diameter), scraper conveyors may be needed for higher capacity.
How do I prevent long chips from jamming the conveyor?
Three approaches: (1) improve chip breaking at the drill — adjust chip breaker geometry or parameters so chips break into shorter segments; (2) install a scraper conveyor instead of a hinge belt — scrapers handle long chips without jamming; (3) install a chip crusher or shredder before the conveyor to reduce chip length.
How do I size a chip conveyor for a deep hole drilling machine?
Calculate the chip volume per hole (bore cross-section × depth), multiply by 1.5 for chip swell factor, multiply by parts per hour to get hourly chip load, and specify a conveyor with minimum 2× the hourly chip load capacity. Also consider: chip type (long chips require wider trough), whether the conveyor serves multiple machines, and peak production rates rather than average.
What maintenance does a chip conveyor require?
Daily: check for jams and smooth movement. Weekly: check belt tension and sprocket alignment, lubricate bearings. Monthly: inspect belt or chain condition, check trough for wear, inspect motor and gearbox. Scraper conveyors require more frequent chain maintenance than hinge belts. Magnetic conveyors require occasional magnet cleaning and eventual magnet replacement.
The chip conveyor is often the most overlooked system on a deep hole drilling machine — until it jams and stops production. Matching the conveyor type to the chip type produced by the drilling method is the key to reliable operation. A scraper conveyor for long gun drilling chips and a hinge belt for broken BTA chips will give the fewest problems. This article reflects industry practice as of 2026.
