ISO 8956:1986

Overview

ISO 8956:1986 - "Acceptance conditions for copying attachments, integral or otherwise, for lathes - Testing of the accuracy" - defines accuracy tests and acceptance conditions for hydraulic and electric servo‑controlled copying attachments used on general‑purpose, normal‑precision lathes (centre lathes, vertical boring machines, capstan lathes, copying lathes). It supplements existing lathe acceptance standards by describing both special tests (repeatability, dead‑zone, sensitivity) and practical machining tests (profile and dimensional checks) for single‑axis and two‑axis copying systems up to 180° included angle. Mechanically controlled copying attachments and multi‑axis systems beyond 180° are excluded.

Key topics and requirements

• Scope & applicability
  • Applies to servo‑controlled copying attachments (hydraulic and electric), single‑axis systems and two‑axis systems (≤180°).
  • Supplements general lathe tests for normal precision machines.
• Special tests
  • Repeatability (positioning): tests using template and dial gauge; example permissible deviation shown in the standard is 0.005 mm for certain repeatability checks.
  • Dead‑zone and sensitivity: micrometer and dial gauge setups measure control dead band and discrete movement counts; permissible deviations and observation procedures are defined.
  • Tests are performed at ends and mid‑stroke of copying slides and with the copying unit in operating position or integral with the machine.
• Practical tests
  • Machining of standardized test pieces (chuck or between‑centres) to check diameters, shoulders, tapers, facing profiles and taper regularity.
  • Specified test piece dimensions and machining sequences for single‑axis and two‑axis systems; permitted dimensional deviations and inspection methods (micrometer, depth gauge, straight edge, slip gauges).
• Measurement methods
  • Use of micrometers, dial gauges, depth gauges, straight edges, slip gauges with defined mounting and measuring directions.
• Permissible deviations
  • ISO 8956 lists numerical tolerances for different tests (examples in the standard include mm and inch equivalents) and requires manufacturer‑specified measuring pressures for some checks.

Applications

• Acceptance testing of copying attachments during:
  • Machine tool manufacturing and final inspection
  • Supplier quality control and incoming inspection
  • Workshop qualification, commissioning and periodic verification
• Ensures copying attachments meet accuracy required for profile duplication, precision turning and production where template tracing is used.

Who should use this standard

• Machine tool manufacturers and designers of copying attachments
• Quality assurance engineers and metrology labs performing lathe acceptance testing
• Purchasing and commissioning teams buying lathes with servo‑controlled copying units
• Maintenance and repair teams verifying restored accuracy after service

Related standards

• ISO 1708 - Acceptance conditions for general purpose parallel lathes
• ISO 3655 - Acceptance conditions for vertical turning and boring lathes
• ISO 6155 (part references) - Acceptance code for machine tools
• ISO 230‑1 - Geometric accuracy testing of machine tools

Keywords: ISO 8956:1986, copying attachments, lathe accuracy testing, servo‑controlled copying, acceptance conditions, test pieces, repeatability, dead zone, permissible deviations.