Drill Bit Angles: Unlock Perfect Holes in Any Metal!
Achieving optimal hole quality in metalworking demands precision, and a critical factor is selecting the correct drill bit geometry. Drill bit point angles, particularly, influence chip formation and cutting efficiency. The National Institute of Standards and Technology (NIST) provides comprehensive material property databases that are essential for understanding how different metals respond to drilling forces. For instance, high-speed steel (HSS) drills, a common tool in workshops, perform best with specific point angles depending on the target material. Understanding Morse taper systems, used for securely mounting drill bits, also contributes to achieving accurate hole diameters. Therefore, what angle should the point angle on a drill bit be for general purpose and soft metal drilling depends heavily on these factors and proper application using tools like a drill press.
Image taken from the YouTube channel TheRepairSpecialist , from the video titled How to Angle a Drill Bit ‘Using a SIMPLE TRADE SECRET’ (by Craig Kirkman) .
Understanding Drill Bit Angles for Metal Drilling
The geometry of a drill bit, particularly the point angle, dramatically affects its performance when drilling into metal. Selecting the correct angle ensures clean, efficient holes, minimizes walking, and extends the life of the bit. The "point angle" is the angle formed by the two cutting edges at the tip of the drill bit. This explanation focuses on determining the optimal point angle for general-purpose and soft metal drilling.
General Purpose Drilling
For general-purpose drilling, encompassing materials like mild steel, aluminum alloys (that aren’t too gummy or soft), and some plastics, a standard point angle is commonly used.
The 118-Degree Point Angle
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Prevalence: The 118-degree point angle is the most common and widely recommended for general-purpose applications. It strikes a balance between cutting ability and durability.
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Advantages:
- Versatility: Works well on a broad range of materials.
- Good Cutting Action: Efficiently removes material without excessive force.
- Reduced Walking: The angle helps center the bit, minimizing wandering, particularly when starting a hole.
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Disadvantages:
- May not be optimal for extremely hard or very soft materials.
Recommended Materials for 118-Degree Angle:
- Mild Steel
- Aluminum (medium hardness)
- Brass (medium hardness)
- Copper (medium hardness)
- Some Plastics
Soft Metal Drilling
Drilling soft metals like aluminum (particularly gummy grades), copper, and brass requires a different approach to prevent the bit from "grabbing" or "digging" into the material.
The Role of a Smaller Point Angle
A smaller point angle reduces the aggressiveness of the cutting edge, making it less likely to snag in soft metals. This minimizes the risk of tearing, deformation, and chatter.
The 90-Degree Point Angle
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Benefits:
- Aggressiveness Reduction: The reduced angle makes the bit less prone to snagging.
- Cleaner Holes: A shallower angle typically results in cleaner, more accurate holes in soft metals.
- Improved Control: Better control reduces the likelihood of the drill bit wandering.
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Drawbacks:
- Slower Cutting: Can cut slower compared to 118-degree drills in other materials.
- Requires More Pressure: May require more applied pressure while drilling.
Recommended Materials for 90-Degree Angle:
- Aluminum (soft, gummy alloys)
- Brass (soft)
- Copper (soft)
- Lead
- Zinc
Alternative Point Angles for Soft Metals
While 90 degrees is a good standard, some specialized drill bits for very soft or plastic materials might use even smaller angles, approaching 60 degrees. The appropriate angle will depend on the specific material properties.
Point Angle Summary Table
| Material Category | Recommended Point Angle | Advantages | Disadvantages |
|---|---|---|---|
| General Purpose | 118 Degrees | Versatile, good cutting action, reduces walking. | May not be optimal for very hard or soft materials. |
| Soft Metals | 90 Degrees | Reduces aggressiveness, cleaner holes, improved control, less likely to snag. | Slower cutting, may require more pressure. |
Alright, that’s the scoop on drill bit angles! Hopefully, now you have a better handle on what angle should the point angle on a drill bit be for general purpose and soft metal drilling. Go get those holes drilled just right!
