Preparation & Setup

Material Considerations

• Thickness:

  • Thin sheets (<3mm): Risk of bending; use step drills or punch tools.

  • Thick sheets (>3mm): Requires slower speeds, lubrication, and sharp bits.

• Metal Type:

  • Aluminum: Soft, prone to sticking—use high RPM and lubrication.

  • Stainless Steel: Hard, work-hardens—use low RPM, cobalt bits, and cutting oil.

  • Mild Steel: Standard HSS bits work well; moderate speed.

Workpiece Clamping

• Use vise clamps or magnetic fixtures to prevent vibration.

• For thin sheets, sandwich between scrap wood or aluminum to reduce burring.

Drill Bit Selection

Drill Bit Geometry

• Point Angle:

  • 118° (general use).

  • 135° (harder metals, less walking).

• Sharp Cutting Edge: Prevents excessive heat and burrs.

Drilling Process

Step 1: Marking & Center Punching

• Use a scriber or sharpie for precise marking.

• Center punch to prevent drill bit walking.

Step 2: Pilot Hole (For Larger Holes)

• Start with a smaller drill bit (1-3mm) before final size.

• Reduces force and prevents distortion.

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Step 3: Optimal Speed & Feed

• Too fast → Overheating, bit wear.

• Too slow → Work hardening (stainless steel).

Step 4: Lubrication & Cooling

• Aluminum: WD-40 or kerosene (reduces chip sticking).

• Stainless Steel: Cutting oil (prevents work hardening).

• Mild Steel: Optional, but extends bit life.

Step 5: Peck Drilling (For Deep Holes)

• Retract the bit occasionally to clear chips and prevent clogging.

During Drilling:

• Use backing material (wood/aluminum under sheet).

• Slow down before exiting to minimize tear-out.

After Drilling:

• Deburring Tools: Hand deburrer, countersink bit, or file.

• Vibratory Tumbling: For mass-produced parts.

Alternative Methods for High Precision

Common Mistakes & Fixes