The Difference Between Sharpening and Reconditioning

In most shops, "sharpen the drill" is the default call whenever a drill stops performing. It's a reasonable reflex — but it's not always the right intervention. There's a meaningful distinction between sharpening and reconditioning, and conflating the two leads to either wasted money or drills that don't perform the way you need them to.

Sharpening: Restoring the Cutting Edge

Sharpening is the simpler and more common service. The objective is to remove the worn or damaged portion of the cutting lips and re-establish a sharp edge with the correct geometry for that drill type.

On a standard 118° or 135° split-point HSS drill, sharpening touches:

• The cutting lips (primary cutting edge): Material is removed from the clearance face to expose fresh HSS below the wear flat or chipped zone
• The relief angle: Maintained or restored to spec during the grind
• The lip length symmetry: Both lips ground to equal length and equal angle

What sharpening typically does NOT address: web growth from accumulated sharpenings, margin land wear, flute geometry changes, or point thinning (unless specifically included).

A good sharpening brings a worn drill back to cutting performance. It's appropriate when the drill has normal, expected wear — cutting lip wear flats within 0.005–0.010" wide — has been sharpened fewer than 4–5 times, and the diameter hasn't been reduced more than 5% through previous sharpenings. For most shops running steady production work, sharpening is the right call 70–80% of the time.

Reconditioning: Full Geometry Restoration

Reconditioning is a more comprehensive intervention. The goal is to restore the drill's complete geometry — not just the cutting edge, but the point geometry, web thickness, margin condition, and sometimes flute integrity.

A full reconditioning service addresses:

Web thinning: Every sharpening moves material removal further up the drill body, which means the web (the solid core between the flutes) appears thicker at the new tip. A drill that started with a 0.020" web at the tip can have a 0.040" or 0.060" web after several sharpenings. A thick web dramatically increases thrust force because the chisel edge has to tear through more material. Reconditioning includes point thinning to restore proper chisel edge geometry.

Lip angle and geometry reset: On a machine like the WinsloMatic, full geometry can be re-established from scratch — lip angle, relief angle, and point angle set to spec.

Split point restoration: Many high-performance HSS drills have split points that reduce thrust by 35–50% compared to a conventional 118° point. Split points wear and degrade through repeated sharpening. Reconditioning re-establishes the split point geometry.

Diameter check and margin evaluation: Reconditioning typically includes verifying remaining diameter. If the drill has been ground down significantly, it may need to be re-designated for a smaller size or retired.

The Web Growth Problem in Detail

This is the most important technical reason to choose reconditioning over sharpening on an older drill.

A new 3/8" HSS drill has a web thickness at the tip of approximately 0.050–0.060" for a 135° split point. Each sharpening removes material from the point end, moving the tip toward the flute's larger-web section. After 5–7 sharpenings, the web at the new tip can be 0.090–0.120" — double or triple the original.

The chisel edge at that web thickness isn't cutting. It's extruding and tearing material in the center of the hole, requiring significantly more thrust force. Studies of standard drill geometry show that a 0.060" web requires roughly 40–60% more thrust force than a properly thinned 0.020–0.025" web. On a 3/4" or 1" drill, that's significant machine load and can cause breakage in difficult materials.

Web thinning as part of reconditioning solves this completely. The web is relieved back to near-OEM thickness, and the drill behaves like it did when new.

When to Choose Each

Sharpening is appropriate when:

• Drill has fewer than 4–5 previous sharpenings
• Web growth isn't yet causing thrust force problems
• Failure mode is normal cutting edge wear
• Turning around a large batch where economics favor lighter service

Reconditioning is appropriate when:

• Drill has been sharpened multiple times and center-walking or high thrust is observed
• Split point geometry has degraded
• Drill was damaged and needs significant regrind
• Going into a high-precision application where geometry matters
• Taking over tooling from another shop with unknown sharpening history

Cost and Economics

Reconditioning costs more than sharpening — typically 40–70% higher for the same drill size. The economic case for reconditioning is clear when:

• The drill is large (3/4" and above) where tooling cost justifies higher service investment
• The drill is a specialty type (parabolic flute, straight flute, subland) with high replacement cost
• Thrust force problems are causing machine wear or fixture damage
• The drill is going into a tight-tolerance application where geometry matters

For small drills (under 1/4"), the economics often favor replacement over reconditioning unless you're buying by the box and want to maximize utilization.

A Practical Decision Tree

1. Has the drill been sharpened more than 4 times? No → Sharpening. Yes → Evaluate for reconditioning.
2. Is thrust force higher than expected, or does the drill walk on entry? Yes → Web has grown. Reconditioning with web thinning needed. No → Sharpening is fine.
3. Is this going into a precision application (tolerance under 0.005")? Yes → Reconditioning. No → Sharpening sufficient.
4. Is the drill size 3/8" or larger? Yes → Reconditioning likely economical given drill cost. Under 1/4" → Consider replacement.

When you mail drills to MachinistPost, we evaluate each drill and note if we recommend full reconditioning vs. standard sharpening. You get a real assessment based on what's in front of the grinder.