Which standard defines the terminology for defects mentioned in IS 656?

IS 707 (Glossary of terms applicable to timber technology and utilization).

How is the girth of a plywood log measured?

Girth is typically measured at the exact mid-length of the log, and it should represent the underbark measurement. If measured overbark, a standard deduction must be applied.

Can any timber species be used for plywood logs?

No, the standard provides specific lists of approved timber species (e.g., Gurjan, Teak, Mango) that possess the right density, peeling characteristics, and durability for plywood manufacture.

IS 656

: 1988

Logs for Plywood

CurrentSpecializedSpecificationMaterials Science · Timber and Timber Stores

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This standard covers the requirements for timber logs intended for the manufacture of plywood. It outlines the suitable species, dimensional measurements, grading categories, and permissible defects for logs used in rotary peeling or slicing into veneers.

Logs for Plywood

Quick Reference Values

Length allowance for cross-cuttingAt least 10 cm

Measurement of lengthMeasured from the shortest distance between the two parallel planes at the ends

Measurement of girthMeasured at the mid-length of the log underbark

Sweep (curvature) toleranceRestricted based on log grade (typically measured as maximum deviation from a straight edge)

Practical Notes

Logs should be meticulously inspected for metallic inclusions (nails, fencing wire, etc.) before peeling to avoid severe damage to the lathe knives.

Prompt end-coating of harvested logs is highly recommended to prevent rapid moisture loss and subsequent end splitting, which reduces veneer yield.

Center rot or hollow heart defects are particularly critical to check, as the lathe chucks require a solid core to grip and rotate the log during peeling.