How to use an edge finder

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Step 1 – Check workpiece

Check that your workpiece is clean and the edges are smoothed.

This will ensure that the edge finder works accurately.

Step 2 – Clamp workpiece in machine vice

Clamp the workpiece in a vice underneath the spindle of the machine.

Step 3 – Mount edge finder

Mount the edge finder in a collet or drill chuck and secure the tool to the spindle of your machine.

The centre of the shank will represent the centre of the spindle.

Step 4 – Move probe off-centre

Move the probe of the edge finder off centre so you can see the two parts wobble when the machine is turned on.

Step 5 – Turn on machine

Turn the machine on, setting the spindle to run at 1000RPM (revolutions per minute).

Step 6 – Move table

Move the table of the machine longitudinally on the x axis so that the bottom of the edge finder just touches the part.

As the edge finder approaches the edge of the part, it will start to wobble less.

Eventually the tool will become centred and will run true (turn smoothly without wobbling).

Step 7 – Zero x axis

As soon as this happens, zero the x axis on the digital readout display (DRO).

Step 8 – Bring part away

Bring the part away from the edge finder.

Step 9 – Move edge finder towards part

Move the edge finder in again towards the edge of the part to check the accuracy of the location of the edge.

However, the spindle of the machine is not yet centred over the edge.

Step 10 – Lower table of machine

Drop the knee of the machine (lower the table) so the edge finder clears the top of the part.

Step 11 – Move table by half diameter of probe

To position the centre the spindle directly over the true edge of the part, you need to move the table further by half the diameter of the probe of the edge finder.

E.g. if the diameter of the contact probe is 0.2 inches, you will need to move the table a further 0.1 inches (0.2÷2 = 0.1), until the DRO reads 0.1 inches on the x axis.

Step 12 – Zero x axis

Zero the x axis on the DRO once more.

You can then use the corner connecting the two edges as a reference point from which to machine features such as holes or grooves.