Tool Wear

The seven basic types of Tool Wear:

1. Cratering– An erosion of the flat just below the full length of the outside angle.

2. Outside Corner Breakdown– Once the corner breaks down, the margin starts to rub and hole size gets tight.

3. Built-up Edge– Also called 'welding', this condition causes rough, irregular-size holes.

4. Pickup on Margin– Pickup is a 'smearing' of the workpiece material which adheres to the margin.

5. Wear on Margin– Occurs when the margin, which should be in clearance, rubs on the periphery of the hole.

6. Burn on Outside Angle– This condition is a precursor to breakdown of the outside corner.

7. Chipping– Can occur on the point, the inside and outside angle, outside corner, and sometime on the margin.

A Word of Caution!

It should be noted that all the above conditions (with the possible exception of built-up edge) must be completely removed when regrinding the drill tip. Tools with built-up edge often clean themselves once the contributing causes are eliminated. However, before resuming production, inspect tool for overall damage and assure it's consistently running 'clean', and that your hole now has acceptable finish.

If you catch any tool problem early on, you'll remove .005– .010" in regrind. Should you allow the problem to go unattended, removal could amount to 1/8" or more (a loss in tool life of 12 or more regrinds.)

The Gundrilling Handbook includes a complete section on Tool Wear,
defining the causes of and solutions for the above conditions.

When combined with the Handbook's Troubleshooting Charts,
you've got an unbeatable problem solving combination.

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