| Workpiece capacity | Maximum turning diameter, work height, table load, and clearance for fixtures. | Choose capacity around the largest regular job, with practical room for chucking and tool access. | Allow additional capacity for production fixtures, loading equipment, and occasional oversize parts. | Compare the part’s finished and rough dimensions with the machine’s usable—not just advertised—working envelope. |
| Control system | Axis count, conversational programming, shop-floor usability, probing support, and operator experience. | Manual or simple CNC controls can suit one-off work when skilled operators are available. | CNC controls with stored programs, tool offsets, and repeatable setup routines help reduce cycle-to-cycle variation. | Run a representative program and check how easily operators can recover from tool changes, alarms, and interrupted cycles. |
| Accuracy and rigidity | Required bore size, roundness, surface finish, thermal stability, and cutting forces. | Prioritize a rigid machine in good condition; plan for measurement and finishing passes on critical features. | Look for stable positioning, repeatable offsets, and sufficient stiffness for the intended material and cut. | Inspect ways, bearings, spindle condition, backlash, and test-cut results; confirm acceptance criteria with measured parts. |
| Tooling and boring range | Tool interface, boring-bar reach, holder availability, tool changes, and access to standard inserts. | A flexible set of common boring bars and holders can cover a broad mix of jobs without excessive setup cost. | Preset tools, repeatable tool positions, and duplicate tools for high-use operations can shorten changeovers. | Check that holders, bars, inserts, and any special adapters are available and suitable for the machine’s interface. |
| Automation | Part loading method, cycle consistency, unattended-running needs, and chip or coolant handling. | Manual loading is often practical for small batches, heavy parts, and frequent job changes. | Powered clamping, repeatable loading, probing, or material-handling integration may benefit stable, recurring work. | Confirm part weight, lifting access, guarding, clamping sequence, and safe operator access before adding automation. |
| Setup and changeover | Fixture changes, setup documentation, program storage, and time between different jobs. | Favor accessible workholding and straightforward adjustments when jobs vary frequently. | Dedicated fixtures and documented setups can improve repeatability on recurring parts. | Estimate total setup time using a real job, including lifting, alignment, tool setting, proving out, and inspection. |
| Materials and chip control | Material mix, chip form, coolant delivery, filtration, and chip removal. | Confirm the machine can handle the shop’s materials with manageable chip clearing during operator-attended cutting. | Reliable chip evacuation and coolant management are important for longer or repeated production cycles. | Trial representative materials and cutting conditions; inspect chip flow, coolant coverage, and access for cleaning. |
| Utilities and floor space | Machine footprint, foundation, power supply, access route, and service clearances. | Check that the machine can be installed and serviced without disrupting nearby work areas. | Include space for conveyors, loading equipment, guarding, and material staging where needed. | Verify installation drawings, electrical requirements, floor loading, delivery access, and maintenance clearance. |
| Maintenance and support | Parts availability, service access, manuals, lubrication systems, and technician coverage. | Favor a machine with accessible service points and a maintenance plan suited to available staff. | Assess planned maintenance intervals, spare-tool and spare-part strategy, and response arrangements for downtime. | Review service records and manuals; inspect lubrication, guarding, safety devices, and the condition of critical components. |
| Overall selection | Balance part requirements, operator capability, throughput, installation cost, and future work. | Choose flexibility and manageable setup over unused capacity or automation. | Choose repeatability and dependable cycle support when part mix and volume justify the investment. | Score shortlisted machines against actual parts, a sample program, a test cut, and a site-installation review. |