Picking between a CK-6140 and a CK-6150B flat-bed lathe is easier than most people think. Forget the brochure talk — watch three numbers: max turning diameter, spindle bore, and between-centers. The CK-6140 offers Φ420 swing, Φ66 bore and 750mm between centers; the CK-6150B steps up to Φ500 swing, Φ82 bore and 1000mm between centers. One is for small-to-medium precision work, the other for bigger, longer and heavier cuts — choosing wrong means paying twice.

1. Spec Comparison (official figures from Rui'an)

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2. How to choose — three rules

1. Workpiece up to Φ400, mostly precision / non-ferrous / small parts → CK-6140. 2000rpm variable speed and a friendlier price.
2. Workpiece Φ400-500, or shafts over 750mm long → CK-6150B. The 1000mm between-centers is the hard requirement only this machine meets.
3. Heavy roughing, big torque (steel, interrupted cuts) → CK-6150B. A2-8 nose, Φ82 bore, and geared low-speed ranges deliver real cutting torque.

3. FAQ

Q1: Can the CK-6140 turn a Φ450mm disc? No. Max swing is Φ420 — a Φ450 part will hit the cross slide or guards. For discs over 450mm, go with the CK-6150B (Φ500).

Q2: Can both machines feed Φ80 bar stock? No. CK-6140 bore is Φ66; Φ80 bar won't pass. CK-6150B with its Φ82 bore can pair with an Φ80 bar feeder. Always check spindle bore before buying a bar feeder — the most common mistake in machine selection.

Q3: Are the speeds enough for steel? Yes. CK-6140 tops at 2000rpm for cleaner small-part finishing; CK-6150B peaks at 1600rpm but its geared ranges give much more torque at low speed for heavy steel cutting.

4. Bottom line

Budget precision work with bore needs ≤Φ66 → CK-6140. Bigger parts, longer shafts, heavy cutting, or bar stock ≥Φ70 → CK-6150B. Not sure? Send us the max turning diameter, part length and bar size — Rui'an engineers reply with a recommendation within 24 hours.