Gun Drilling
Gun drilling is a deep-hole process that sends coolant through a long single-lip tool and carries chips back along an external flute.
How Gun Drilling works
- Pressurized coolant travels through the tool to the cutting edge.
- Chips return through the tool's external channel and must be evacuated without packing.
- A guide bushing or prepared pilot supports entry and establishes alignment.
- Machine alignment, tool condition, coolant cleanliness, pressure and workpiece support govern hole quality.
What to compare
| Diameter/depth | Required range and depth-to-diameter ratio for the actual material. |
|---|---|
| Coolant | Pressure, flow, filtration, temperature control and fluid compatibility. |
| Configuration | Rotating tool, rotating workpiece or combined rotation. |
| Guidance | Guide bushing, steady support, pilot preparation and tool-change method. |
| Verification | Straightness, diameter, finish, runout and inspection method. |
Used-equipment inspection checklist
Verify the machine
- Drill a representative hole and verify more than entrance diameter.
- Inspect guide bushings, tool supports and spindle alignment.
- Measure coolant pressure/flow and review filtration condition.
- Check chip evacuation over the full intended depth.
- Document tooling, bushings, pumps and fire/mist controls included.
Verify the transaction
- Match the serial number and configuration to the seller's description.
- Identify every included and excluded accessory in writing.
- Confirm power, air, coolant, foundation, rigging and relocation requirements.
- Record a time-stamped operating demonstration and measured result.
- Price missing service, software, tooling and recommissioning before comparing offers.
Why this term matters in the used-machine market
Search results and listings often compress a complete production system into one label. Buyers should translate that label into capacity, condition, control generation, included tooling, serviceability and demonstrated output. Sellers improve credibility by disclosing those facts instead of repeating a brochure headline.
Market value is also specific to timing and buyer fit. A capable machine can trade poorly when its configuration is hard to relocate, support or redeploy; a common platform with documented maintenance, current controls and proven output may attract a wider buyer pool.
Related machine-tool terms
Frequently asked questions
Why not use a standard twist drill?
At high depth-to-diameter ratios, coolant delivery, guidance and chip evacuation become limiting; gun drilling is designed around those constraints.
Does the tool or the workpiece rotate?
Machines may rotate the tool, the workpiece or both, depending on the application and straightness strategy.
Sources and further reading
Source roles are explicit: linked organizations describe their own products, programs or technical guidance. The Machine Blue Book independently organizes and interprets that material for education and used-equipment due diligence. A citation is not an endorsement, sponsorship or guarantee.
- UNISIG — Gun Drilling. Deep-hole machine-tool builder explanation of gun-drill coolant and chip evacuation. Reviewed September 26, 2026.
- IMTS — IMTS Technology Sectors. Primary classification of metal removal, quality, automation, software, tooling and workholding sectors. Reviewed September 26, 2026.
See the complete source register, research methodology and editorial standards.