If you’re considering buying a used Star JNC-16 (Swiss-type/sliding head lathe), it’s a good idea to go into the deal with your eyes wide open. These machines are very capable but like any precision equipment, used ones come with risks. Below are detailed professional tips & red-flags to watch out for — things that can save you a lot of trouble & expense.

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What is the JNC-16 — Key Specs & What to Value

First, knowing what the original machine is supposed to do helps you spot deviations. Some relevant specs from sellers / data:

• Maximum turning diameter: ~16 mm.
• Spindle speed: up to ~7,500 rpm.
• Bar / workpiece length capacity: often ~150 mm or more.
• Control: often Fanuc (various), e.g. Fanuc OT or Fanuc 2T-A.

Understanding these helps you verify whether what you’re buying matches what’s advertised, or whether wear / modifications have reduced performance.

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What to Inspect / Test — Avoiding Costly Mistakes

Here are what I’d consider musts in inspection, plus pitfalls people sometimes overlook.

Area	What to Check / Test	Why It Matters / Common Problems
Machine History & Usage	Ask for service records: hours, maintenance (lubrication, guides), any rebuilds. Ask what parts have been replaced (e.g. guides, spindle, bearings).	Over-use or neglect leads to wear. Without history you can inherit problems.
Accuracy / Alignment	Check alignment of the guides (sliding head, guide bushing, turret if present). Measure run-out of spindle, tailstock or guide bushings. Inspect whether the machine can produce parts within your required tolerances.	Wear in guides or spindle bearings causes inaccuracy; repairing that can be expensive.
Spindle & Bearings	Listen for noises while running; check vibrations; measure run-out; check oil seals for leaks; check spindle taper or chuck/hole condition.	Spindle replacement or bearing work is costly and downtime is long.
Control System & Electronics	Test the Fanuc (or whatever control): its buttons, display, memory, parameter backup. Check for errors (e.g. RAM parity, axis ready/VRDY errors). Ask whether replacement boards are still available.	Older controllers may have obsolete or hard-to-get spare parts. A control failure can kill the machine. For example, people have reported RAM parity errors with Fanuc OT on JNC-16.
Bar Feeder / Guide Bushing	If the machine has a synchronized or non-synchronized bar feeder, check its condition. Inspect the guide bushing (wear ring) for excessive wear.	A worn guide bushing reduces quality of finish; bar feeders are often expensive and less likely to be in stock if it’s old.
Turrets / Tool Holders / Tool Posts	Inspect tool posts (front/back), number of tools, tool holding condition, wear. Check whether tooling is standard or specialized.	Poor tool holding causes chatter, breakage, subpar finish. Also tooling for Swiss lathes tends to be specialized and may be costly to replace.
Cooling / Lubrication Systems	Are the pumps, filters, coolant lines working? Is there rust or clogging? Inspect oil mist or lubrication delivery to ways & guides.	Without good lubrication / coolant, wear accelerates; overheating or seizing can occur.
Condition of Ways / Surface Finish / Guards	Look for nicks, rust, gouges in sliding surfaces. Inspect surface finish of inside, chipping, etc. Guards and covers matter for safety and debris control.	Restoring damaged ways or repairing rust can be very expensive. Also safety and chip control affect machine longevity and working environment.
Power / Electrical Setup	Ensure proper voltage, phase, grounding. Look for signs of electrical damage: burnt wiring, smoked components, moisture damage. Check that power requirements match what you have.	Electrical issues are hazardous; mismatches cause failure. Also difficult to upgrade or repair if aged or special parts.
Parts Availability & Support	Check whether spare parts (bearings, seals, control boards, guides) are still available; whether there’s any aftermarket support or used parts.	Without parts, even a small failure can cause long downtime or force costly recreations.
Cost of Transport & Installation	Swiss‐types are precise; moving them poorly causes misalignment or damage. Consider shipping, installation, leveling, calibration cost.	The purchase price may seem good, but logistics can kill the deal.
Trial Run & Load Test	Run it under representative load: produce a part like you plan to, for a period. Watch for temperature drift, stability, repeatability, finish quality.	Machines may run fine light but fail under load; hidden weaknesses (thermal, structural, spindle torque) often show up only under production load.

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Red Flags / “Deal Killers”

These are issues you might want to walk away if present (or negotiate heavily):

• Spindle with excessive run-out or vibration or obvious bearing noise.
• Worn guide bushings or guides beyond repair or requiring full regrind.
• Missing manuals / parameter backups for control system (hard to program or repair).
• Control is obsolete with no source for parts or no backup of software/firmware.
• Rust penetrating critical parts (slides, bed, spindle, inside ways) — extensive rust is hard to clean without affecting accuracy.
• Evidence of flood coolant or coolant leaking into ways or bearings.
• Electrical issues: corroded wiring, water damage, smoke smell.
• Inconsistent maintenance history, or owner can’t provide basic usage stats.
• Price too low (sounds good to be true) — usually means hidden faults.
• No possibility to test under load.

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Negotiation & Warranty Tips

• Have the seller agree to a conditional period: you inspect first, or run test parts before final payment.
• Try to get some guarantee or acceptable terms for parts (if machine fails early).
• Include in your offer the cost of bringing it up to spec: re-alignment, calibration, new tooling. Use that as leverage.
• Ask whether seller can help with setup or training, especially for older control versions.

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Specific Challenges with JNC-16

From what sources show:

• Many of them are quite old (1980s).
• They often use Fanuc OT or similar legacy controllers, with known issues like RAM parity errors.
• Parts may not be as abundant as newer machines.
• Wear in sliding head lathes (guide bushings, spindle bore / guide) tends to be cumulative and tricky to repair.