For all the little but important jobs like this there is the copper washer. Use them on your hydraulic ports, banjo bolts, oil drain plugs and other metal fittings that need to retain pressure but not let it escape. Picking out the correct size and temper for the application can make all the difference between a good seal and a slow leak. This is a quick breakdown of the most common washers and what they are used for. See graphic above.
Crush, or annealed, deforms with torque to fill out small surface irregularities. Flat sealing compresses on flat surface. An inner ring of rubber offers more grip for high pressure uses. These are closer to narrow roles, such as electrical grounding or vibration resistance. Knowing which type of washer it is will keep you from using the incorrect washer for the job.
What Copper Washer Do You Need?
The same goes for material properties. Copper, for example, conducts electricity and heat. It resists a lot of different kind of fluids. It is still pliable at temperatures that will melt out fiber or rubber washers. So the charts in this infographic translate those characteristics into what they mean in terms of practical temperature and pressure limits.
And then there’s the part where they split sizes between metric and imperial so you know which washer matches the type of thread you’re dealing with: An M16 hydraulic fitting vs. A 1/2-inch drain plug.
Once installed, what happens? That depends off the annealing state of the washer. A one-time crush seal is made when soft annealed copper flow into the joint. Half-hard copper is suitable for repeated assembly because it maintains more shape and spring. The infographic clearly marks these tempers. This helps you determine whether to save the washer for multiple uses or replace it with each service interval.
For example: There are pros and cons to using aluminum, steel, or copper. While aluminum is light and inexpensive, it lose strength at lower temperatures. Steel retains heat effectively, but doesn’t bend as well. Finally, copper is highly resistant to corrosion and seals very well; except that it’s a greater threat for galvanic reactions than aluminum. Check out the comparison chart in the infographic to make sure you don’t run into any nasty surprises from a galvanic reaction.
A crushed washer can be re-annealed at home. To do this, heat the component until it is dull red, then drop it into water to quench it and remove the scale. This will return it to a soft state for minor uses such as oil drain plugs. Do not try this with brake or fuel systems where failure has serious potential.
A properly installed copper washer does its job quietly. A mismatched one will cause a leak or a drip. A correctly chosen washer based on material, temper and size becomes a reliable seal that matches the real world conditions of the service.
