The Bernardo STG 42 tap grinder sharpens M16 – M42 taps with 2, 3, and 4 flutes, adjustable point angle of 5° – 30°, speed 4,400 rpm, 0.25 kW single-phase 230V motor. Weight 24 kg. Distributed in Italy by Krollit as an official Bernardo distributor since 2007.
-
Working range (taps): M16 – M42
-
Number of flutes: 2, 3 and 4
-
Point angle: 5° – 30°
-
Rotor speed: 4,400 rpm
-
Motor power: 0.25 kW – 230V single-phase
-
Weight: 24 kg
Who uses the STG 42 and for what
The Bernardo STG 42 grinder reconditions HSS and carbide taps with 2, 3, and 4 flutes in the M16 – M42 range: instead of replacing a worn tap, it can be resharpened in a few minutes, restoring the cutting edge profile with precision. An M42 HSS tap costs 20–80 euros; sharpening it with the STG 42 takes 5–10 minutes and a trained operator. With 24 kg and single-phase 230V, it can be used on any workshop bench. In Krollit's customers' workshops, it is used by mechanical workshops, mold makers, and CNC machining centers that regularly consume taps.
Who is the Bernardo STG 42 for?
| Profile |
Compatibility |
Reason |
| Hobbyist |
Suitable |
For hobby use, taps wear out rarely — the ROI on the grinder is long. Useful if frequent drilling is done. |
| Professional mechanical workshop |
Ideal |
M16 – M42 range: reconditions the most used taps in mechanical workshops without frequent replacement costs. |
| Industrial production |
Ideal |
In production with high tap consumption, the grinder pays for itself in a few months. |
Not suitable for: taps outside the M16 – M42 range; taps with 6+ flutes (check compatibility); drill bit sharpening (consider DG 13 MD or DG 32).
Technical specifications
| Specification |
Value |
| Working range |
M16 – M42 |
| Number of flutes |
2, 3 and 4 |
| Point angle |
5° – 30° |
| Rotor speed |
4,400 rpm |
| Motor power |
0.25 kW |
| Power supply |
230V – single-phase |
| Dimensions (L × W × H) |
400 × 300 × 310 mm |
| Weight |
24 kg |
Compliance and safety
| Specification |
Value |
| Marking |
CE |
| Directive |
Machinery 2006/42/CE |
Logistics
Bernardo shipping: 5–9 working days (7 days in the South). Original spare parts available with 3–5 working days shipping. Customer support available in Italian.
Frequently asked questions
Does the STG 42 sharpen carbide taps?
Yes. The STG 42 is compatible with HSS, carbide (tungsten carbide) and TiN coated taps. For carbide taps, verify that the included grinding wheel is suitable — for hard metal, diamond or CBN wheels are typically used. Contact Krollit for details on the specific grinding wheel for carbide.
What is the difference between STG 20 and STG 42?
The STG 20 covers taps from M5 to M20 with a 0.16 kW motor (14 kg). The STG 42 covers taps from M16 to M42 with a 0.25 kW motor (24 kg) — for larger taps requiring more grinding power. For workshops working primarily on M16 and below, the STG 20 is sufficient; for taps up to M42, the STG 42 is needed.
Is specific training required to use it?
Yes, more so than for drill bit sharpeners. Tap sharpening requires an understanding of cutting edge geometry (point angle, relief surface). An inexperienced operator can ruin the tap. It is recommended to follow the manual in Italian and practice on already worn taps before sharpening new ones. Krollit provides complete documentation.
Are replacement grinding wheels available?
Yes. Original Bernardo replacement grinding wheels available with 3–5 working days shipping.
Does the STG 42 also sharpen right-hand and left-hand taps?
Yes. The grinder handles both right-hand and left-hand taps with the same basic setup, varying the feed direction during sharpening. The Italian manual illustrates the procedure for both orientations.
