If you’re considering buying a used Kashifuji KN80 CNC gear hobber, it’s a specialized machine tool and there are many potential pitfalls. Getting it right means verifying many mechanical, electrical, tooling, and control aspects. Below are detailed, professional tips & red flags to watch out for.

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What the Kashifuji KN80 Is / Key Specs to Know

Here are the published specs so you know what to expect, and what to confirm when inspecting.

Spec	Typical Value
Max workpiece (gear) diameter	80 mm
Max module (gear tooth size)	Module 4
Axial feed travel (Z-axis)	200 mm
Hob-head swivel (A axis)	±45°
Hob shift travel (Y axis)	~ 130 mm
Hob size (diameter × length)	~ 110 × 180 mm
Hob spindle speed	~ 200-2,660 rpm
Table (C-axis) max RPM	~ 330 rpm
Control example	Fanuc 18I-MB, or Fanuc 31i Model B in more recent models

These are your baseline; any unit you inspect should ideally meet or very closely approach them, unless the seller has clearly noted “downgraded” or “modified”.

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What to Inspect / Test — Detailed Checklist

When you go to see the machine, check/verify the following. Bring measuring gear, test blanks, and ideally someone who knows gear hobbing.

Area	What to Examine / Test	Why It Matters / What Can Go Wrong
Mechanical Alignment & Geometric Accuracy	• Check hob arbor/trunnion run-out: measure with a dial indicator to see wobble in the hob; any run-out can degrade gear tooth profile. • Check work table (gear blank) axis run-out and wobble; check spindle bore of table for wear. • Check swivel (A axis) alignment: hob-head swivel angle should be accurate and lock solidly without play. • Check clamping of the gear blank: how rigid is the fixture, arbor, bearing, tailstock etc. • Check backlash in gear and work spindles, and any feed screws.	Gear shape, tooth profile, pitch, helix error etc. are especially sensitive to misalignment or backlash. Poor alignment leads to errors in helix angle, pitch, run-out, and bad surface finish. Also affects repeatability.
Spindle / Hob Head & Hob Arbor / Drive	• Run hob spindle at different speeds; listen for unusual noises (bearing wear, gear mesh noise). • Inspect hob arbor for any bending or wear; check supports for arbor if present. • Check the condition of hob mounts, collets / clamping mechanism. • Inspect lubrication / oiling of spindle bearings; see if there has been overheating. • Check for how many hours of use under load vs idle.	Hob spindle issues degrade hob life, damage tooth form, reduce surface quality. Arbor issues (bending, run-out) are very problematic. Overheated or poorly lubricated spindle bearings are a common weak point.
Axes, Feed Mechanisms & Slides	• Move all axes (especially Z, Y, A, C) through full travel; check for smooth motion, no binding or stick-slip spots. • Check feed screws / ballscrews for backlash or play. • Check slide or way condition: wear, scoring, rust, pitting. • Check responsiveness of feed rates, tilting, table indexing etc. • Test whether hob-head shift (Y) and alignment work correctly.	Axis wear causes inaccuracy in tooth profile, helix error, varying gear quality. If slides are worn or unlubricated, precision degrades quickly.
Control System, Electronics & Software	• Power up the CNC / control: check display, panel switches, safety interlocks. • Review fault log / alarm history (if available): repeated errors in axes, spindle overloads etc. • Inspect electrical cabinet: wiring, heat damage, moisture, cleanliness. • Check that software / firmware versions for the CNC and motion control are available and preferably not obsolete. • Confirm that operator manuals, maintenance / parts manuals are present or obtainable. • Test dry operation (without hob) of all motions, indexing, swivels etc.	Electronics often fail or degrade first; if key control boards are obsolete, replacement is difficult or expensive. Safety interlocks missing or faulty increase risk of accidents and damage. Missing documentation makes maintenance, repairs, and future replacement harder.
Tooling, Hob & Cutter Condition	• Inspect the hob tool(s) used: condition of teeth, wear or damage. • Check if tool holders are straight, correctly mounted. • Check inventory of hobs and fixtures: do you have spares or will you need to purchase new ones (often costly). • Check if arbor holders, tailstock, workholding fixtures are complete and in good condition. • Check hob head shift travel & precision.	Worn or damaged hobs degrade gear quality and increase scrap. If tooling is scarce or specific, cost may be high. Also mismatched or worn fixtures cause misalignment or vibration.
Operational Testing / Trial Cutting	• If possible, provide a gear blank (or similar) and run a test hob; inspect gear tooth profile, surface finish, pitch accuracy, helix error, run-out. • Test full speed feeds, under load, not just idle movement. • Test changeovers / swiveling of hob head; observe whether the precision holds. • Observe cycle times, chatter, vibration during cutting. • Run a longer run test to see thermal drift or wear over time (e.g. after 1-2 hours of operation).	Many issues only show up under real load: heat expansion, chatter, dropping accuracy over time. Also identifies whether machine maintenance has been good.
Maintenance History & Usage	• Ask for usage hours, especially hours under load vs idle. • Service records: oil changes, bearing replacements, alignment checks, retiming or backlash compensation adjustments. • Environment: was machine used in clean or very dusty, dirty, or harsh environment (humidity, temperature swings)? • Any history of crashes, overloads, or past damage. • Whether machine was serviced by authorized personnel or appropriate gear-machine techs.	Good history reduces risk. Harsh environments or neglect make hidden damage likely. Previous damage may have been patched up but still show up later.
Parts Availability, Support & Tooling Costs	• Confirm whether spare parts (Hob arbors, bearings, gears, controls, feed screws, etc.) for KN80 are still available, either via Kashifuji or aftermarket. • Check whether the CNC / motion controllers / drives / feedback elements are supported. • Estimate costs of hobs, fixtures, tooling, and how many hobs you’ll need. • Check labor and cost to tune / calibrate / realign machine once delivered. • Availability of qualified service or repair techs in your region.	If parts are rare or expensive, maintenance cost will be high. Having to ship parts internationally adds downtime & cost. Tooling is a recurring cost; if you must order expensive imported hobs, that adds up.
Safety, Ancillaries & Infrastructure	• Check guarding, safety interlocks, emergency stops. • Check chip removal / coolant systems: is coolant used; what condition; are filters / pumps functioning; is cooling for hob or workpiece adequate. • Floor space & foundation: gear hobbers are heavy, need stable floor, vibration damping. • Electrical supply: voltage, phase, clean power, whether the location supports the required power. • EHS (environment / safety) compliance: local safety standards, dust / coolant disposal, noise etc. • Transport & installation requirements: lifting points, weight, rigging complexity.	Even a mechanically perfect machine can be problematic if installation is poor or safety missing; poor coolant or cleanliness accelerates wear; poor foundations or vibration cause precision loss. Transport and installation cost often underestimated.

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Red Flags / “Deal Breakers”

Here are conditions which, unless the price is greatly reduced and you have budget to remediate, should make you very cautious or walk away:

1. Excessive run-out or wobble in hob arbor or table spindle, especially that cannot be eliminated with standard service.
2. Large backlash in feed screws or axes that are used for hob head shift / gear blank positioning; especially if backlash compensation is non-functional.
3. Hob head swivel mechanism is loose, damaged, or does not lock solidly at ±45°; wear in pivot bearings visible.
4. Hob spindle bearing noise, overheating, or signs of wear; humming, etc.
5. Poor condition of injected tooling / no menus / missing fixtures or hobs. If tooling set is missing or worn, cost to replace may be steep.
6. Control or drive electronics are outdated / obsolete, fault logs indicate recurring errors; if spare cards or modules are unavailable.
7. Missing or inoperable coolant / lubrication / chip conveyor systems. If dry cutting was used inappropriately, may have accelerated damage.
8. Environmental damage: rust, moisture in mechanical or electrical areas; neglected maintenance.
9. Safety features missing or compromised: guards, interlocks, emergency stops not working.
10. No test job possible or seller refuses cutting test under working conditions.

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Negotiation Tips & Hidden Costs to Budget For

When deciding on your offer, make sure you include these “hidden” or later costs in your calculations, so you don’t get hit by surprise expenses:

• Cost of refurbishing hob spindle bearings, arbor alignment, re-grinding or truing hob arbor.
• Cost of re-aligning or re-scraping any worn ways, slides, swivel joints.
• Replacing worn fixtures, tool-holding, gear arbors, perhaps even hobs with proper tooth profile.
• Cost of new tooling, hobs, fixtures. These can be costly, especially if module 4 or high quality.
• Electrical / CNC / drives repair or upgrade costs, spare parts, possibly software licensing.
• Transport, rigging, import costs; heavy machine, careful mov­ing.
• Installation, alignment, calibration, level / foundation work.
• Safety compliance or upgrades needed for your location.
• Cooling / coolant / filtering / chip removal / waste disposal setup.
• Operator training or set-up time: getting the machine programmed and running parts, developing your hob profiles etc.