Edge & Centre Finders

Edge & Centre Finders

Edge finders and centre finders allow a machinist to accurately establish the position of a workpiece edge or hole centre relative to the machine spindle. Accurate workpiece location is the basis of accurate machining — if the reference position is wrong, every feature machined from it will be wrong by the same amount. AIMS Industrial supplies mechanical edge finders, wobble bars, electronic edge finders, and centre finders for milling machine setup and CNC workpiece referencing.

Mechanical Edge Finders (Wobble Bars)

The standard mechanical edge finder consists of a shank and a floating contact tip held by a spring in approximate alignment with the shank axis. The spindle is run at low speed (typically 500–800 RPM) and the contact tip is brought slowly into contact with the workpiece edge. As long as the tip is not in contact with the work, it wobbles around the shank axis; when it contacts the workpiece, the tip aligns with the shank and runs concentrically. As the machine table is advanced further, the tip suddenly kicks out — this point, minus half the contact tip diameter, is the workpiece edge. For a 10mm tip diameter, the edge is 5mm from the spindle centreline at the kick-out position. Mechanical edge finders are accurate to approximately ±0.005mm in steady conditions.

Electronic Edge Finders

Electronic edge finders use an electrical circuit through the spindle and tool body — when the contact tip touches the workpiece (which must be conductive), the circuit closes and a LED or buzzer indicates contact. Electronic edge finders do not require spindle rotation and can be used on stationary spindles, making them preferable for machines where running the spindle before workpiece referencing is inconvenient. Accuracy is comparable to mechanical types.

Centre Finders

Centre finders locate the centre of an existing hole or boss. A cone-tipped centre finder is inserted into the hole; the taper centres the tool in the bore and the spindle can then be set to the hole centreline. This is the standard method for picking up the centre of drilled holes in setup for follow-on operations on a milling machine.

Order Edge and Centre Finders from AIMS

AIMS Industrial stocks edge finders and centre finders for milling machine setup and CNC work holding. Accurate workpiece referencing is one of the most time-consuming elements of manual and semi-CNC machining — the right instruments make this faster and more reliable. For help selecting the right instrument for your machine and application, contact our team.