A used machine can be a great deal or a money pit. Here’s what to check, ideally with a repair tech along.
See it under power
Never buy a machine you can’t see running. Watch it home, change tools and cut if possible.
Spindle
- Run it through the speed range and listen for noise
- Check runout with a test bar
- Check the taper for damage or fretting
- Ask about spindle hours and any rebuilds
Axes and ways
- Check backlash on each axis
- Look for scored ways and damaged way covers
- Ask for a ballbar test if the seller allows it
Control and electrical
- Look at the alarm history for repeat alarms
- Check that options you need are actually enabled
- Open the cabinet: look for burnt smells, heavy dust or coolant
- Get the parameter backup and manuals with the machine
Hydraulics, lube and coolant
- Look for leaks and sludge in tanks
- Check chuck, turret and tool changer function
Get a pro inspection
For a few hours of a tech’s time, a pre-purchase inspection can save you from a machine that needs a spindle or drives on day one. Many companies in our directory offer this.
Need a repair tech?Find a verified repair tech near you, or send one request.
Find CNC repairMore guides for shop owners
Guide · 2 min readBallbar tests and laser calibration, explained for shop ownersWhat these tests measure, when you need them, and what the report tells you.Guide · 2 min readHow to get the most out of a CNC service visitSmall things that cut the tech's time on site and your bill: scheduling, access, an operator on hand and the info to have ready.Guide · 2 min readCNC preventive maintenance checklist: daily, weekly, monthly, yearlyA simple, printable PM schedule for mills and lathes that operators can actually follow.Guide · 2 min readRepair or replace? How to decide on an old CNC machineA straight way to decide whether to fix, rebuild, retrofit or replace an aging machine.