How to Choose a Drill Bit Sharpener for HSS and Carbide Drills

A dull twist drill wastes cycle time, burns holes, and walks off-center. Buying a drill bit sharpener is cheaper than throwing bits away — but only if the machine matches the steel you actually grind. This guide is for workshops comparing a portable drill sharpening machine for HSS (high-speed steel) versus carbide drills, using the same specification layout as the MR-13B product page.

1. Why HSS and carbide need different grinding wheels

Almost every MRCM portable drill bit sharpener ships with a CBN wheel and lists an SD / SDC wheel as an option. That is the line between a machine that restores HSS and a machine that can grind carbide without glazing the wheel.

MR-13B drill bit grinder — the portable drill bit sharpener used as the specification reference in this guide.

2. Specifications that actually decide the purchase

For a commercial-research buyer, six fields on the product table matter more than the rest:

• Grinding range — smallest and largest diameter the collets can hold.
• Point angle — 118° for general steel, 135° for harder materials. MRCM portable machines typically cover 95°–135°.
• Wheel type — CBN (HSS) standard, SD/SDC (carbide) optional.
• Functions — point angle, lip relief, and point splitting / thinning.
• Motor and speed — 120 W / 4400 rpm on the 13-series; 250 W on MR-26A.
• Collet set — factory collets vs optional half sizes and Φ14–Φ15 chucks.

3. MR-13B specification (from the official product page)

The MR-13B is the model to start from: more accurate than MR-13A, still a 10-second portable grind, with web thinning and lip-relief grinding. Parameters follow zjmrcm.com/products/drill-sharpener/269.html.

Features behind those numbers: grinding is accurate and rapid with no skill required; the DC motor holds frequency; a bearing shaft and locking unit keep the chuck true; and the machine can adjust the central-point size so the web matches the material and spindle speed. Lip-relief and point-splitting holes are both on the body — that is why MR-13B is marketed as more accurate than MR-13A.

4. How MR-13A, MR-13B and MR-13D differ

The 13-series share the same footprint (about 32 × 18 × 19 cm) and the same CBN / SD wheel logic. The difference is how much of the drill geometry you can grind independently.

Choose MR-13A if operators only need a repeatable point and a stable relief. Choose MR-13B when you want adjustable relief and a reputation product that already includes point splitting. Choose MR-13D when carbide or stainless work needs a thinned web so chips escape and the drill does not walk.

Point angle, lip relief and web thinning are the three geometries a drill sharpening machine must control.

5. Match grinding range to the drills on the rack

A drill bit sharpener that cannot hold the shank is the wrong machine. Use diameter first, material second:

• Φ3–Φ13 (optional Φ15) — MR-13A / MR-13B / MR-13D / MR-13H. Most maintenance kits and CNC starter drills.
• Φ3–Φ20 — MR-20G, with ER20 and ER25 collets. Better for industrial users who grind all day.
• Φ12–Φ26 (optional to Φ32) — MR-26A, 250 W motor, 31 kg. Large fabrication bits.

If the shop mixes 6 mm HSS jobbers with 18 mm carbide, one 13-series machine plus one MR-20G or MR-26A is cleaner than forcing every diameter onto a single chuck. All of these models still follow the same wheel rule: CBN in the crate, SD for carbide.

6. Buyer checklist

What “no skill required” actually means on the floor

On MR-13B the setting is mechanical, not CNC. You read the drill diameter on the scale, lock the collet, line the chuck with the grinding hole, and rotate left and right. Point grinding and relief grinding are separate holes on the body. That is why a family workshop and a production cell can share the same drill sharpening machine: the geometry is in the fixture, not in the operator’s hand.

Set diameter on the scale, insert the chuck on the parallel line, grind in about 10 seconds.

Compare drill bit sharpener models

Every portable drill sharpening machine below ships with a CBN wheel for HSS; add the SD wheel when carbide is in the mix.