1. Lumber Drying Reasons to dry lumber --Dimensional stability Methods
--Dry wood is stronger than wet wood
--Dry wood is more durable against decay and insect damages
Methods
--Air drying with natural elements (temperature, humidity, wind)
Moisture Content ≤ 19%
--Kiln drying: drying under controlled environments
Moisture Content ≤ 15%

2. Drying Procedures Sorting for Grades, thickness, species, sometimes MC
based on drying rates
Stacking & stickering
Good stacking & stickering
ensures a successful drying
operation
Air-drying

3. Bad Stacking & Stickering

4. Kiln Drying Basic Elements --A compartment to enclose lumber
--Heating (coils)
--Vents and steaming device to
regulate relative humidity
--Fans for air circulation

5. Planing Lumber is knife planed Where F = feed speed
Basics of planing
Planing is done by passing lumber through
a series of planer cutterheads. Surface
qaulity is defined by length of knife marks
(Ft) and depth of knife marks (h).
Ft = 12 x F NT
Where F = feed speed
N = Revolutions per minute
T = Number of knifes on cutterhead
Lumber is knife planed

6. Planing Operation

7. Sanding (Machining with coated abrasives)
Basics
Wood-based composite panels
are finished with coated abrasive,
which consists of backing, resin
sizing and minerals (abrasives).
Abrasives
--Garnet (Hardness 7.5)
--Aluminum oxide (9.5)
--Silicon carbide (9.6, diamond 10)
Grit size
The higher the number the finer is the grits, 60, 80, 100,……

8. Lumber Grades and Grading
Hardwood Lumber Grades:
Hardwood lumber is graded according to size and appearance

9. Softwood Lumber grades
Softwood lumber is graded for strength

10. Methods of Grading Softwood Lumber
Visual Grading: Examining each piece for strength- reducing defects and assign a strength ratio
(% strength remained) relative to a piece without any defect.
Machine Grading: Flexing each piece to an extent not
to cause any damages, followed by calculating MOE
(modulus of elasticity) and estimating MOR (modulus
of rupture). Grading also can be done with ultrasound
Method. Both methods are non-destructive evaluation
(NDE) .