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How to use an edge finder

Shop for Centre and Edge Finding Sets

Step 1 Check that your workpiece is clean and the edges are smoothed. This will ensure that the edge finder works accurately.

Step 1 – Check workpiece

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

This will ensure that the edge finder works accurately.

Wonkee Donkee says: 'If the edges of the part are not smooth, you will need to deburr them by using either a hand held deburring device such as a file or scraper, or a machine such as a grinding wheel.'
Step 2 Clamp the workpiece in a vice underneath the spindle of the machine. Step 3 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 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 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 the machine on, setting the spindle to run at 1000RPM (revolutions per minute).

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 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 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).

When the edge finder makes contact with the edge, the two cylindrical parts will become offset. When the edge finder makes contact with the edge, the two cylindrical parts will become offset.
Step 7 As soon as this happens, zero the x axis on the digital readout display (DRO).

Step 7 – Zero x axis

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

Step 8 Bring the part away from the edge finder. Step 9 Move the edge finder in again towards the edge of the part to check the accuracy of the location of the edge.

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.

When the edge finder becomes offset you have reached the edge of the part. However, the spindle of the machine is not yet centred over the edge. When the edge finder becomes offset you have reached the edge of the part.

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

Step 10 Drop the knee of the machine (lower the table) so the edge finder clears the top of the part.

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 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 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 the x axis on the DRO once more.

Step 12 – Zero x axis

Zero the x axis on the DRO once more.

The edge finder (and spindle) will now be positioned directly over the centre of the edge of the part. The edge finder (and spindle) will now be positioned directly over the centre of the edge of the part.
Repeat this procedure to locate the opposite edge. You can then use the corner connecting the two edges as a reference point from which to machine features such as holes or grooves. Repeat this procedure to locate the opposite edge.

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

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