Is Tab Washer the Best Bolt Locking Method?

Tab washers or Nord-Lock washers? Finding the ultimate bolt securing system is no easy task. Here is a guide to making the right choice.

	Tab Washers	Nord-Lock Wedge-Locking
Locking capability	Relatively good	Reliable
Range	Normally not available for large sizes.	M3-M130 (standard range)
Temperature	Same temperature characteristics as regular bolts/nuts.	Same temperature characteristics as regular bolts/nuts.
Assembly/disassembly routines	Complex and time-consuming assembly/disassembly. Requires enough space, additional tools and a skilled operator.	Simple and rapid assembly/disassembly. No special tools or preparation required.
Control of clamp load	Friction conditions must first be verified in order to predict the clamp load.	Linear relationship between torque/load – thus possible to predict the clamp load.
Risk of damage to assembled parts	Some risk. Requires deformation of the washer through shocks, which can damage the assembled parts.	No risk. Fine impression marks on bolt head/nut, as well as underlying surfaces.
Reusability	Not reusable	Reusable
Environment and safety	Recyclable. Manual assembly routines and long assembly time increase risk of injury, human error and damage to parts.	Recyclable. Minimal risk of human injury or error. Rapid assembly time results in minimal exposure in dangerous areas.
Lubrication	Possible to lubricate.	Possible to lubricate.
Use in confined spaces	Limited use in confined spaces, due to complex assembly requirements.	Suitable for use and easy to assemble in confined spaces.
Use with through holes	Time-consuming and difficult to use with through holes. Note that washers on both sides of the assembled parts are required.	Suitable. Note that washers on both sides of the assembled parts are required.
Use with hex cap screw (ISO 4762)	Not possible	Possible
Counterbores	Not possible	Possible
Life cycle cost (LCC)	High. Short life cycle. A large number of units must be purchased as washers are neither reusable nor standardized.	Low. Relatively high price per unit. Long life cycle. Standardized and reusable items improve stability and minimize maintenance costs.