🛠️ Example: Simple Metal Drilling Jig
This jig is designed to drill two holes in a rectangular metal sheet (Workpiece) with the position of the two holes being precise and consistent every time the work is repeated.
🧩 Jig components
Jig Plate: A thick steel or aluminum plate with holes drilled into it for inserting drill bushings to guide the drill bit.
Stop Blocks or Locator Pins: Parts that attach to the jig base plate to determine the position of the workpiece.
📐 Applying the 3-2-1 principle
The 3-2-1 principle is used to limit the movement of the workpiece in six directions (Six Degrees of Freedom) so that the workpiece is always stationary and in the correct position when placed on the jig.
1. 3-Direction Limit (3 Points): Limit rotation (Roll, Pitch) and Z-axis movement (Up-Down).
Reference: Use 3 reference points (Locator Pins or base surface of the jig) in contact with the bottom surface of the workpiece.
Result: The workpiece cannot move up or down (Translate Z) and cannot rotate around the X and Y axes (Pitch and Roll rotation is restricted).
In this example: the entire surface of the jig base plate that supports the workpiece.
2. Two-way constraint (2 Points): Yaw constraint and X-axis movement.
Reference: Use two reference points (e.g. stop blocks) that touch the primary side of the workpiece.
Result: The workpiece cannot move along the X-axis (left-right) and cannot rotate around the Z-axis (Yaw rotation is restricted).
In this example: the stop blocks A and B are fixed to the jig base plate.
3. 1 Direction Limit (1 Point): Limiting movement along the Y-axis.
Reference: Use one reference point (e.g., single stop block) that touches the secondary side of the workpiece.
Result: The workpiece will no longer be able to move along the Y-axis (front-back).
In this example: is the stop block C that is fixed to the jig base plate.
✅ Summary of work
When the sheet metal is placed on the jig and pushed into contact with the three stop blocks (A, B, and C) and clamped, the workpiece is completely locked in position, so that no matter how many times the operator places the workpiece, the drilled holes will always be in the same position. This allows for high-precision, repeatable production , and fast , without the need for re-measuring or marking.
| main | Jig Fixture , 3-2-1 Principle , Manufacturing Engineering , Tools , Mechanical Engineering |
| concept | Accuracy , Repeatability , Locating Principle , Positioning |
| Work samples | Drilling Jig , Metalworking , Drilling Jig , Tool Design |
| component | Drill Bushing , Stop Block , Clamping |
| language | Thai language , manual , learning |
First picture: Shows an overview of the drilling jig with a metal plate (workpiece) and the "Precision Drilling" concept.
Photo Caption: "PRECISION DRILLING - Jig & Fixture for Perfect Repetition"
Second picture: Shows the first 3 directions (3 Points) constraint, focusing on the base surface of the workpiece.
Caption: "3-2-1 LOCATING PRINCIPLE: STEP 1 - 3 POINTS: Base Plane (Limits Z, Roll, Pitch)"
Third picture: Shows the next 2 directions (2 Points) constraint, focusing on the side edges of the piece.
Caption: "3-2-1 LOCATING PRINCIPLE: STEP 2 - 2 POINTS: Primary Side (Limits X, Yaw)"
Figure 4: Shows the final 1-direction (1 Point) restriction, focusing on the end edge of the workpiece, so that the workpiece is completely locked.
