Resharpening a drill bit by hand on a bench grinder is a real skill. It takes practice. Done right, you get a bit that cuts almost as well as new. Done wrong, you get a bit with unequal lip heights, wrong angles, and a center that wanders on entry. Understanding what you're trying to achieve before you touch the wheel makes the whole process faster to learn.
This isn't about grinding jigs or attachments — those help, and if you're doing production resharpening, use one. This is about hand technique: how to hold the bit, what motion to use, and how to verify you got it right.
Before you can resharpen one, know what you're aiming for:
Two equal lips. The cutting edges on both flutes need to be the same length and meet at the center. Unequal lips mean only one edge is doing most of the cutting — the bit wanders, drills oversized, and wears out faster. This is the most common resharpening mistake.
Correct point angle. Standard HSS bits use 118°. Cobalt bits and bits designed for harder materials typically use 135°. The angle is measured as the included angle at the point — 118° means each lip is set at 59° off the drill axis.
Positive lip clearance. The face behind each cutting edge needs to be relieved (angled back) so only the edge contacts the work. If there's no clearance, the trailing face of the lip drags against the material and the bit can't cut. This is the relief angle and it's the other common mistake — grinding the lip flat or with negative relief.
No flat on the chisel edge. The center of the drill (the chisel edge) should be small and correctly angled. A big flat chisel edge means excessive thrust force is needed to advance the drill.
Hold the bit in your right hand near the point, your left hand back near the shank for control. The bit should be approximately horizontal to the wheel face, with the cutting lip you're working on presented to the wheel.
The motion is a combination of two movements happening simultaneously:
This sounds more complicated than it is. In practice, it's a smooth motion: present the lip, rotate slightly as you advance, lift off, repeat. The key thing to resist: don't push hard. Light contact and consistent motion beats aggressive grinding every time. You're removing very little material per pass.
This is where most hand resharpening goes wrong. After grinding each lip, stop and sight down the point. You're looking at the two cutting edges meeting at center. If one is longer than the other — and it will be, at first — you can see it clearly from this angle.
The fix is always: grind the longer lip. Grind the short one more and you make the problem worse. Find the longer one, take a few careful passes, check again. Using a drill point gauge (a simple stamped metal tool that's $5 at any supplier) removes the guesswork. The gauge has a V-notch you rest each lip in and a straight edge you compare against — if both lips hit the same mark, they're equal.
After grinding, check the relief behind each cutting edge. Hold the bit up to a light source and look at the face behind the lip at an angle. You should see the face angling away from the cutting edge — back and down. If the face is flat or angles the wrong way, the bit will rub instead of cut.
A common way to verify: press the freshly sharpened bit against a smooth metal surface (the flat of a machinists square works). If the point contacts and the heel (back of the lip face) rises slightly, clearance is correct. If the whole face lays flat, you have zero clearance. For standard 118° bits, aim for about 12–15° of relief behind the lip.
Hand technique produces functional bits for general drilling. For precision work — location work, close-tolerance holes, or drilling materials with no margin for a wandering start — machined resharpening on a proper grinding fixture produces tighter geometry than hand technique can consistently deliver. A properly resharpened production bit can hold lip height symmetry within a thousandth or two. Hand resharpening on a bench grinder, even skilled hand resharpening, usually runs a few thousandths of lip height variation. Fine for most shop work. Not fine for precise fixture drilling or when you need repeatable hole location.
Use a medium-grit aluminum oxide wheel (46 or 60 grit) for HSS. It removes material fast enough to be efficient without burning the point. Fine grit wheels (80+) take too long and you risk putting heat into the bit while you're trying to work.
Keep the bit cool. Dip in water between passes. If the point ever gets too hot to touch, you've likely drawn the temper at the cutting edge — that bit won't hold an edge well even after grinding.
It takes a dozen bits to get the feel. After that, you can put a working edge back on a standard HSS drill in under two minutes. For harder-to-replace cobalt or carbide-tipped bits, or for production volume, send them out to someone with the right equipment.
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