Forest Utilisation Chapter 3: Felling Rules, Felling Methods and Conversion of Timber

Forest Utilisation Notes · Chapter 3

Chapter 3: Felling and Conversion

Felling season and rules, stump height, felling with axe, axe and saw, saw alone and by roots, log making, trimming allowance, sawn forms of timber, sleepers, and hand versus machine sawing.

SeasonRulesMethodsLog makingSawn formsSawingRevisionMCQ quiz

1. Felling season

• In the Himalaya above about 2000 m, felling starts from April onwards, after the snow melts.
• In the plains and lower hills, felling is done from October to March.
• Winter is the best season: sap is low, labour is free from farm work, and the timber is less liable to fungal and insect attack and to splitting.

2. Felling rules

• On hill slopes, fell trees uphill (towards the slope) so they fall a short distance and do not break.
• Fell in vertical strips, laying stems in herring-bone fashion so they can be slid or rolled down.
• Start felling from the top of the slope and work downhill.
• Concentrate fellings in one place to save supervision and transport.
• Do not fell trees across roads, streams, depressions or other felled trees.
• Keep stumps low: not more than 15 to 30 cm. High stumps waste 2 to 5% of the stem.
• Choose the direction of fall so as to cause least damage to the remaining crop and regeneration.

Memory trick: Fell uphill, start from the top, strip by strip, like a fish bone.

3. Methods of felling

Method	How it is done	Notes
Axe alone	A notch (undercut) about 2/3 of the diameter (up to 3/4 in big trees) on the side of fall; back cut 10 to 15 cm above it. The wood left between is the tipping edge (hinge).	Wasteful; old practice
Axe and saw	Undercut with the axe; saw cut from the back 2.5 cm above the undercut; a wedge is inserted once the saw has gone in about twice its blade breadth.	Most common
Saw alone	Both undercut and back cut made with the saw.	Saves 3 to 7% of butt timber
By roots (uprooting)	Roots are dug round and cut; the tree is pulled over with its roots.	Used for sandal, khair and walnut, where the root or stump wood is valuable

Exam point: Sandalwood is uprooted because its roots contain much of the scented heartwood and oil. Khair heartwood is used for katha; walnut burls give the best figured wood.

4. Log making

After felling, the stem is debranched and cross-cut into logs. Log making has four purposes:

• Reduce weight: green timber is 1/3 to 3/4 of the tree's weight.
• Eliminate defects such as rot, crooks and large knots.
• Adapt to transport: lengths that the carrier can handle.
• Adapt to market: lengths the buyer wants.

Produce	Usual length
Logs	5 m or its multiples
Small material	Multiples of 1.5 m
Poles	3 to 15 m
Logs for animal transport	3 to 5 m

Trimming allowance

An extra length is left so that damaged ends can be trimmed. For logs: 5 to 10 cm (10 to 30 cm in large timber). For sawn timber: 7.5 cm in length, 2 cm in breadth and 1.25 cm in depth.

5. Sawn forms of timber

SquaresCompletely squared, rectangular, no wanes.

Waney baulksWhere part of the rounded surface of the log is left at one or more, or even all, corners.

Half baulksWhen baulks are split into two, down the centre, each piece is termed as half baulk.

HakriesThe rounded logs split with axe.

BeamsMore than 4 metre length and end cross section not less than 15 cm.

ScantlingsSquare or rectangular, generally under 15 cm in section.

BlocksPieces of short lengths with square surfaces.

PlanksWooden slabs up to a maximum of 5 cm thickness with varying length and width.

Railway sleepers

Gauge	Track width	Standard sleeper
Broad gauge	167.64 cm	275 cm × 26 cm × 13 cm
Metre gauge	100 cm	183 cm long
Narrow gauge	76.2 cm	about 153 cm long
Light narrow gauge	61 cm	about 153 cm long

6. Hand sawing and machine sawing

Quarter (radial) sawing

Saw cuts follow a radius. The medullary rays appear as lustrous plates giving silver grain. Also called quarter-sawn timber; beautiful and durable.

Tangential sawing

Cuts follow a tangent and expose mainly softer fibrous tissue. Such boards tend to warp in the direction of concavity.

Hand sawing

The most common method in Indian forests; logs are marked with guide lines, propped up and sawn. Wastes 27 to 32%.

Machine sawing

In sawmills in or near forests, made possible by electricity. More accurate, with a higher conversion percentage.

7. Quick revision

• Plains: fell October to March; Himalaya above 2000 m: from April. Winter is best.
• Fell uphill, from top downwards, in vertical strips, herring-bone fashion; concentrate fellings.
• Stump height not more than 15 to 30 cm.
• Axe and saw: saw cut 2.5 cm above undercut; wedge after the saw is in twice its breadth.
• Saw alone saves 3 to 7% butt timber. Uprooting: sandal, khair, walnut.
• Logs 5 m or multiples; trimming allowance 5 to 10 cm for logs.
• Beam > 4 m and at least 15 cm section; scantling < 15 cm; plank up to 5 cm thick; hakries = axe-split logs.
• Broad gauge sleeper 275 × 26 × 13 cm. Quarter sawing gives silver grain.

8. Interactive MCQ Quiz

16 questions. Tap an option to see the answer and explanation, then go to the next question.

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