Sunday, November 17, 2013

Summary - Principles of Jig and Fixture Design

Summary of Principles of Jig Design. Summarizing  the following rules may be given as the main
points to be considered in the designing of jigs and fixtures:

1. Before planning the design of a tool, compare the cost of production of the work with present tools with the expected cost of production, using the tool to be made, and see that the cost of building is not in excess of expected gain.

2. Before laying out the jig or fixture, decide upon the locating points and outline a clamping arrangement.

3. Make all clamping and binding devices as quick-acting as possible.

4. In selecting locating points, see that two component parts of a machine can be located from corresponding points and surfaces.

5. Make the jig " fool-proof "; that is, arrange it so that the work cannot be inserted except in the correct way.

6. For rough castings, make some of the locating points adjustable.

7. Locate clamps so that they will be in the best position to resist the pressure of the cutting tool when at work.

8. Make, if possible, all clamps integral parts of the jig or fixture.

9. Avoid complicated clamping arrangements, which are liable to wear or get out of order.

10. Place all clamps as nearly as possible opposite some bearing point of the work, to avoid springing.

11. Core out all unnecessary metal, making the tools as light as possible, consistent with rigidity and stiffness.

12. Round all corners.

13. Provide handles wherever these will make the handling of the jig more convenient.

14. Provide feet, preferably four, opposite all surfaces containing guide bushings in drilling and boring jigs.

15. Place all bushings inside of the geometrical figure formed by connecting the points of location of the feet.

1 6. Provide abundant clearance, particularly for rough castings.

17. Make, if possible, all locating points visible to the operator when placing the work in position.

18. Provide holes or escapes for the chips.

19. Provide clamping lugs, located so as to prevent springing of the fixture, on all tools which must be held to the table of the machine while in use, and tongues for the slots in the tables in all milling and planing fixtures.

20. Before using in the shop, for commercial purposes, test all jigs as soon as made.

Detailed Explanation of Principles 

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