
#import "/meta-environments/env-features.typ": *

= Bench Grinders

Protohaven has a pair of two-disk bench grinders in the metal shop, useful for removing material from a workpiece.

The first bench grinder (on the left) holds:

- Wire brush wheel, suitable for any material (left)
- Aluminum grinding wheel, suitable for aluminum (right)

The second bench grinder (on the right) holds:

- Coarse grinding wheel, suitable for steel (left)
- Fine grinding wheel, suitable for steel (right)

== Notes

=== Safety

Do not let the workpiece get drawn into the gap between the tool rest and grinding wheel. Keep the work perpendicular to the wheel face, and flat on the tool rest.

Use the entire wheel surface when grinding. Using only one part of the wheel surface will lead to uneven wear, and may lead to pieces of the wheel flying off.

It may be unsafe to grind small workpieces on the pedistal grinders. Consider using vice grips or other custom clamping jigs to keep control of your part and keep your fingers away from danger.

The wire wheel creates a lot of drag on the workpiece, and can catch the edge of a part and fling it violently.

=== Care

- Only grind appropriate materials with each wheel.\
  _Using the wrong material may damage the grinding wheel._

== Parts of the Grinders

=== Front View

#figure(
  image("./images/bench_grinders-annotated.png", width: 100%),
  caption: "An annotated front view of the bench grinders. From left to right, the grinders are set up with: wire brush, aluminum, steel (coarse grit), steel (fine grit)."
)

=== On/Off Switch

Put the switch in the *on* position to turn on the motor in the grinder.

Put the switch in the *off* position to turn off the motor in the grinder. Wait for the grinder to completely spin down before leaving the area.

=== Aluminum Grinding Wheel

The aluminum grinding wheel should be used for aluminum grinding only. Using other materials on this wheel may damage it.

=== Blast Gates

The blast gates control airflow from the grinders to the dust collection system.

Make sure to open the appropriate blast gate and turn on the dust colleciton system before grinding.

=== Coarse Steel Grinding Wheel

The course grinding wheel can be used to rapidly remove material from steels.

This grinding wheel should only be used with steels. Grinding other materials with this wheel may damage the wheel.

=== Fine Steel Grinding Wheel

The fine grinding wheel can be used when a smoother finish is desired, but removes material more slowly than the coarse wheel.

This grinding wheel should only be used with steels. Grinding other materials with this wheel may damage the wheel.

=== Spark Shield

A plastic shield that keeps sparks from flying up at the user. Use the spark shield if your workpiece can be used with it. Always wear personal eye protection (goggles or face shield) when using the grinders.

=== Quench Cup

The quench cup is used to cool down a workpiece that is getting to hot from grinding. Only use water in the quench cups.

=== Tool Rest

Use the tool rest to steady the workpiece while grinding. Be careful not to let the workpiece pinch in the gap between the tool rest and the grinding wheel.

=== Wheel Guard

The wheel guard is an important piece of safety equipment. The guard will help protect you and other shop members if the grinding wheel breaks up under load.

=== Wire Wheel

The wire wheel is useful for softening the edges of cut materials and  cleaning surfaces. Use any material with the wire wheel (but check the results on a test piece first).

== Basic Operation

=== Setting Up

+ If needed, check to make sure there is sufficient water in the quench cup to quench the workpiece.
+ If needed, adjust the tool rest to bring it to within 0.05" of the wheel surface.
+ Adjust the shield so that it will not impede the workpiece.
+ Inspect the grinding wheel you will be using for any chips, cracks, or severe indentations.
+ Open the appropriate blast gate.
+ Turn on the metal grinder dust collection.

=== Grinding

+ Turn on the bench grinder.
+ Hold the workpiece firmly.\
  _Use two hands if needed._
+ Register the workpiece against the tool rest.
+ Present the workpiece to the wheel surface.\
  _Make sure the workpiece does not get pulled down into the gap between the wheel and the tool rest._
+ With steady and gentle pressure, move the surface of the workpiece slowly and smoothly across the face of the wheel.\
  _If the workpiece is getting too hot, cool it in the quench cup._
+ Turn off the bench grinder.
+ Wait until the grinding wheels come to a complete stop before cleaning up.

=== Cleaning Up

+ Turn off the metal shop dust collection.
+ Close any open blast gates.