Buying a used deep hole drilling machine can save 40–60% compared to new. But unlike standard machine tools, deep hole drilling machines have high-pressure coolant systems, long guideways, and rotary unions that are expensive to repair. A systematic inspection separates a good deal from a costly mistake.
Machine History Review
Documents to Request Before Inspection
| Document | What to Look For |
|---|
| Machine serial number and year of manufacture | Verify age and model |
| Original purchase invoice | Confirms original specifications and options |
| Maintenance records | Shows if regular maintenance was performed |
| Spindle runout measurement log | Trend of spindle condition over time |
| Ball screw backlash measurements | Shows wear progression |
| Coolant pump service history | Pump seal and bearing replacements |
| Control system software version | Identifies obsolete control versions |
| List of past alarm codes | Reveals recurring issues |
| Production output records | Shows utilisation levels |
Key Questions to Ask the Seller
- Why is the machine being sold?
- Was the machine running in production before removal?
- What type of parts were drilled (material, depth, tolerance)?
- How many shifts per day did the machine run?
- What is the coolant type and filtration system?
- Have any major repairs been performed?
- Are original electrical and mechanical drawings available?
Structural Inspection
Machine Base and Bed
| Check Point | Method | Acceptable | Reject |
|---|
| Bed level | Precision level across full length | Within 0.02 mm/m | Out of level by 0.05 mm/m+ |
| Bed twist | Level at both ends and centre | Less than 0.03 mm/m | Visible twist |
| Cracks in casting | Visual inspection | None | Any crack |
| Paint condition | Visual | Minor chips OK | Rust indicating coolant damage |
| Way cover condition | Visual | Minor dents OK | Perforated or jammed covers |
Spindle Inspection
| Check Point | Method | Acceptable | Reject |
|---|
| Radial runout at taper | Dial indicator at spindle nose | < 0.010 mm | > 0.020 mm |
| Axial runout | Dial indicator on spindle face | < 0.010 mm | > 0.015 mm |
| Bearing noise | Listen at low and high RPM | Smooth, consistent | Grinding or knocking |
| Spindle temperature | Run at max RPM for 30 minutes | Ambient + 15°C | Ambient + 25°C+ |
| Rotary union seal | Pressurise coolant system (low pressure) | No leakage | Visible coolant leak |
Warning: Rotary union leakage is one of the most common and expensive problems on used deep hole drilling machines. A leaking rotary union at the spindle requires spindle disassembly to replace — typically $2,000–5,000 in parts and labour for a repair that is not visible during a casual inspection.
Guideway and Ball Screw Inspection
Guideway Assessment
| Check Point | Method | Acceptable | Reject |
|---|
| Guideway surface | Visual along full travel | Smooth, no scoring | Visible scoring or pitting |
| Way wiper condition | Visual | Flexible, contacting surface | Hardened, torn, or missing |
| Guideway straightness | Wire method or laser | < 0.01 mm/m | > 0.02 mm/m |
| Lubrication delivery | Check oil at each way point | Oil present at all points | Dry at any point |
Ball Screw Assessment
| Check Point | Method | Acceptable | Reject |
|---|
| Backlash | Dial indicator, axis reverse | < 0.03 mm | > 0.05 mm |
| Axial play | Push-pull on axis | < 0.02 mm | > 0.05 mm |
| Torque variation | Manual axis movement | Smooth full travel | Tight spots or grinding |
| Support bearings | Listen during axis movement | Quiet | Grinding or clicking |
Coolant System Inspection
Coolant Pump
| Check Point | Method | Acceptable | Reject |
|---|
| Maximum pressure | Run pump with flow restricted | Within 10% of rated pressure | 20%+ below rated |
| Flow rate | Measure with flow meter | Within 10% of rated | 20%+ below rated |
| Pump noise | Listen at operating pressure | Smooth | Cavitation or bearing noise |
| Seal leakage | Visual during operation | Occasional drip | Steady stream |
| Pressure fluctuation | Watch pressure gauge | ±2 bar stable | ±5 bar+ fluctuation |
Coolant Tank and Filtration
| Check Point | Method | Acceptable | Reject |
|---|
| Tank condition | Visual interior | Light rust OK | Corrosion perforation |
| Tank cleanliness | Visual | Minor sludge | Heavy sludge build-up |
| Filter housing | Open and inspect | Clean, no damage | Rusted or damaged |
| Coolant return line | Visual from entry point | Clear flow | Blocked or restricted |
Control System Evaluation
| Check Point | Method | Acceptable | Reject |
|---|
| Control power-up | Start control system | Boots without errors | Alarm codes at startup |
| Axis movement | Jog all axes | Smooth in all directions | Jerky or noisy |
| Spindle control | Ramp up and down | Smooth acceleration | Vibration or stalling |
| Coolant control | Turn on/off via M-code | Immediate response | Delayed or no response |
| Screen and buttons | Test all | All functional | Dead pixels or non-functional buttons |
| PLC battery | Check voltage | Above minimum | No battery (program loss risk) |
Test Cut
Minimum Test Cut Requirements
| Test | What It Verifies |
|---|
| Drill a test hole in supplied material | Overall machine capability |
| Measure hole diameter at entry, middle, and exit | Spindle alignment and guide bushing condition |
| Measure hole straightness | Guideway and workpiece alignment |
| Check surface finish | Spindle bearing and feed quality |
| Record coolant pressure during cut | Pump and seal condition |
| Record spindle load during cut | Bearing and motor condition |
Tip: Bring your own material for the test cut. A seller providing the test material may use soft, easy-to-machine material that masks machine problems. Use material similar to what you will be drilling in production.
Valuation Framework
Price Adjustment Factors
| Machine Condition | Price Adjustment vs. Market Average |
|---|
| Excellent — documented maintenance, low hours, recent rebuild | +10–20% |
| Good — running in production, some visible wear | 0% (baseline market price) |
| Fair — visible wear, needs minor repairs | –15–25% |
| Poor — needs major repairs (spindle, guideways, coolant) | –35–50% |
| Not running — cannot be demonstrated | –50–70% |
Repair Cost Estimation
| Repair Item | Typical Cost | Negotiation Leverage |
|---|
| Ball screw replacement (one axis) | $5,000–12,000 | Deduct full cost |
| Guideway reconditioning | $8,000–20,000 | Deduct 50–75% of cost |
| Spindle bearing replacement | $3,000–8,000 | Deduct full cost |
| Coolant pump rebuild | $2,000–5,000 | Deduct full cost |
| Control system retrofit | $15,000–40,000 | Deduct if obsolete |
| Way cover replacement | $2,000–5,000 | Deduct full cost |
FAQ
What is the most important thing to check on a used deep hole drilling machine?
The rotary union (coolant seal at the spindle). A leaking rotary union requires spindle disassembly to repair, costing $2,000–5,000. Run the coolant system during the inspection and check for leaks at the spindle.
How many hours on a used machine is too many?
Deep hole drilling machines typically last 15–25 years with proper maintenance. Running hours alone are less important than maintenance history. A machine with 20,000 hours and documented maintenance is often better than one with 5,000 hours and no service records.
Should I buy a used machine without running it?
No. Never buy a used deep hole drilling machine without seeing it run under power. The coolant system, spindle, and axis drives can only be properly assessed during operation. If the seller cannot demonstrate the machine under power, assume the worst and price accordingly.
What is a fair price for a used deep hole drilling machine?
Typically 40–60% of the new machine price, adjusted for age, condition, hours, and included accessories. A 10-year-old machine in good condition with documented maintenance is typically worth 40–50% of new replacement cost.
Can I get warranty on a used deep hole drilling machine?
Some specialised dealers offer 30–90 day warranty on used machines. Private sales are typically as-is. Factor the cost of a post-purchase inspection and potential repairs into your budget when buying without warranty.
Inspection requirements vary by machine type, age, and application. Consider hiring an independent machine tool inspector for high-value purchases. This article reflects industry practice as of 2026.
