The Tyzack Wiggler & Centre Finder Set - TT16987 is a precision measuring and setup tool primarily used by machinists and model engineers on machinery like milling machines and drill presses.

Purpose

The set is invaluable for accurately locating and aligning the spindle of the machine with specific points on a workpiece, such as:

• Edges: Finding the exact edge of a part (edge-finding).
• Centers: Finding the center of a scribed line, a punch mark, or an existing hole (center-finding).
• Shoulders or Grooves.

Contents and Function

A typical 5-piece wiggler set, like the TT16987, usually includes a main holder (collet/chuck) with a 3/8 inch shank, and several interchangeable attachments:

1. Wiggler Chuck/Holder: The main body that is mounted in the machine's spindle. The attachments push-fit into a collet in the body.
2. Needle Point / Centre Finder: Used to align the spindle directly over a scribed line or center punch mark. The point is brought down close to the mark, and when the spindle is directly centered, the point will appear to stop "wiggling" or oscillating.
3. Ball Contact (e.g., 0.25" dia): Used for locating edges or the center of existing holes. When run against an edge, the ball is pushed into alignment, and when it "kicks out," the center of the spindle is a distance equal to half the ball's diameter from the edge.
4. Disc Contact / Edge Finder (e.g., 0.100" dia): Similar to the ball contact but with a flat disc, often used for more precise edge finding.
5. Offset Indicator Holder / DTI Holder: An adapter to hold a Dial Test Indicator (DTI), allowing the user to sweep and check the concentricity of holes, mandrels, or the true alignment of a vise on the machine table.

The attachments are held by a ball swivel joint, which allows them to "wiggle" off-center when the spindle is rotating, but they settle into a true, non-wobbling rotation when the tip makes contact with the work and is brought perfectly onto the axis of rotation or at the correct offset.