Washers- Spread the load
Published by Spaenaur Inc
February 1st, 2023
Washers help provide a consistent torque-tension relationship.
"If your favorite tool is a washer, you’ll soon believe that friction is the enemy, and everything can be solved with just the right amount of pressure.”— Evelyn Torque
Washers improve the appearance of the assembly. Some washers have the specific purpose of improving appearance and for others it is the nice by-product of using a washer.
Most of the energy applied in tightening the fastener goes into overcoming friction. Half that friction is in the surface between the turned fastener (bolt head or nut) and the surface of the assembled component.
A hardened washer will help reduce and control this friction so that a more predictable tension will be developed for a given amount of torque. Conical washers and some very special washer designs use controlled deflection to affect tension control.
Functions and Benefits of Washers:
1. Preventing Loosening
- Washers prevent the joint from coming loose.
- Washers that help prevent loosening are generically called Lock Washers. There are many different types.
2. Acting as Spacers
- They act as spacers to accommodate longer bolt lengths.
- Using washers as a spacer is effective and common. Long bolts stay tight better than short bolts.
3. Material Isolation
- Washers insulate or isolate dissimilar metals in the assembly.
- Dissimilar metals in contact with each other are a major source for electrolytic corrosion. Separating them with a washer that is friendly to both materials can prevent this corrosion.
4. Surface Protection
- Washers protect the surface of the assembled components from damage during tightening. This is especially important with soft materials such as aluminum or plastic and materials with a painted surface.
5. Sealing
- They function as a seal or gasket.
- A soft copper washer can seal an oil drain plug.
- A metal washer with bonded rubber on it can seal out rain in metal building assembly.
6. Electrical Conductivity & Grounding
- Washers provide positive electrical conductivity or grounding in electrical and electronic assemblies.This is one of the main functions of toothed lock washers.
7. Loosening/Tightening Indicators
- They can indicate if the threaded fastener is properly tightened or that it has come loose.
- This function can be the sole purpose of some very special “washers” or a side benefit of some very ordinary washers.
8. Application-Specific Functions
- Washers can provide a very application-specific function.
- Washers such as torque washers, spherical washers, tab washers, and clipped washers have features that are unique to their purpose.
9. Load Distribution
- Washers help spread the clamp load over a larger surface area.This is especially important with less than optimal joints with soft surface materials, joints with slots, and joints with over-sized holes.