Wood Screws - Withdrawal Force
Allowable withdrawal load force.
Allowable withdrawal load or force of a common wood screw into side grain perpendicular to the fibers of seasoned dry wood can be expressed as
F = 2850 SG2D (1)
where
F = allowable withdrawal load or force - lb per inch of penetration (lb/in)
SG = specific gravity of oven dry wood
D = diameter of screw (in)
Note the difference between allowable load and failure load. Allowable load includes design and safety factors and ranges typically between 2 and 10. Depending on the case allowable load is normally 10 - 50% of the failure load.
Example - Screw Allowable Withdrawal Load
The specific gravity of Canadian Spruce is 0.45 . The diameter of no. 10 screw is 0.190 inches . The withdrawal force per inch of penetration can be estimated as
F = 2850 (0.45)2(0.190 in)
= 109 lb per inch of penetration
Screw Withdrawal Force Calculator
Imperial Units
Metric Units
Related Topics
-
Fasteners
Bolts, nuts and threaded rods - torque, tension and loads. -
Miscellaneous
Engineering related topics like Beaufort Wind Scale, CE-marking, drawing standards and more.
Related Documents
-
Drill Bits - Conversion Chart
Convert between drill bit dimensions - gauge numbers, inches and mm. -
Glue-Laminated Timber - Dimensions
Common sizing of glue-laminated timber. -
Hardwood and Softwood Species
Species of hardwood vs. softwood. -
Hardwood and Softwoods - Recommended Drill Bit Speeds
Hardwood and softwood drill speed chart. -
Hardwood Lumber - Dimensions
Sizing of hardwood lumber. -
Machine Stress Rated (MSR) and Machine Evaluated (MEL) Lumber
Grading of lumber in North America -
Metric Threads - Clearance Holes and Tapping Drill Sizes
Recommended clearance holes and drill tap sizes. -
Nails and Spikes - Withdrawal Force
Allowable withdrawal load for nail and spikes. -
Softwood and Hardwood - Structural Strength Classes
Strength classes, bending stress and mean density of hardwood and softwood -
UNC and UNF - Unified Coarce and Unified Fine Inch Threads
ANSI/ASME B1.1 Unified National Thread - UNC Coarse series and UNF Fine series. -
US Machine Screws - Dimensions
Machine screw diameters. -
US Wood Screws - Nominal Sizes
Wood screws - nominal sizes vs. diameters. -
US Wood Screws - Pilot Holes
Hard wood and soft wood pilot holes, shank clearance holes and countersink diameters. -
Wood Beams - Strength of Material
Bending and compression strength of wood species used in beams. -
Wood Headers - Max. Supported Weight
Weight supported by a double or triple wood headers. -
Wood Species - Densities
Densities of various wood species - apple, ash, cedar, elm and more. -
Wood Species - Moisture Content and Weight
Weight of green and air-dried fire wood. -
Wood, Panel and Structural Timber Products - Mechanical Properties
Density, fibre stress, compressive strength and modulus of elasticity of clear wood, panel and structural timber products.