GTX Academy: Concrete drills – SDS-Plus and SDS-Max
2025-09-18
NEO TOOLS power tool accessories – big changes in our brand!
2025-10-23Successful metal drilling starts with two decisions: drill bit length (DIN 338 or DIN 340) and the right tip geometry (C or E correction). Below, we explain when to choose a DIN 338 and when to choose an elongated drill bit (DIN 340), and how the 135° split point (type C) and centering tip (type E) work. We throw in practical rules for getting started, mistakes with quick solutions, and finally we provide sample SKUs from the GTX (GRAPHITE/NEO TOOLS) range so you can replenish your toolbox right away.
Shear correction: C vs E - what does it mean and when to use which one?
- - Type C - split point 135°. The split point blade self-centers, requires less pressure, "bites" into the material faster and "slides" less on the surface. Recommended for carbon steels, stainless steels and harder alloys - especially when drilling by hand or without first making a hollow point.
- - Type E - "centering tip". Centers very well in thin sheets and pipes, causes fewer burrs when drilling, can be guided precisely in thin material; note - it is more sensitive to impact, best for thinner sections and unhurried work.
Shear correction is the appropriate modification of the tip of the drill bit, improving centering, cutting initiation and guidance stability.
Selection at a Glance:
- Harder steels / hand drilling → C (split 135°).
- Thin sheet / pipe, edge control → E (centering).
DIN 338 vs DIN 340 - which length to choose?
- DIN 338 - standard length
Cylindrical shank; choose for typical depths when greater rigidity and clean, repeatable work "by hand" or on a bench drill counts. - DIN 340 - extended series (long series)
Longer drill bits for deeper holes and reaching through profiles. They require lower RPMs, lower feed rates and intermittent work (chip cleaning).
Comparative table of DIN 338 and DIN 340 standards
|
Criterion |
DIN 338 |
DIN 340 |
|
Length / stiffness |
Standard / higher rigidity |
Longer / lower stiffness |
|
Application |
Typical depths, "hands-on" and table work |
Deeper holes, reaching through profiles |
|
Technology |
Universal |
Lower RPM, lower feed rate, interruptions |
|
Start in material |
With scoring or split point (C) |
Split/C and careful feed |
Drill bit material: HSS, HSS-Co, HSS TiN - when which?
- HSS (high-speed steel) - universal work in structural steels and non-ferrous metals.
- HSS-Co (M35, cobalt) - higher heat/abrasion resistance, for stainless and hard-to-cut steels; blends well with C 135° geometry.
- HSS TiN (titanium nitride coating) - lower friction, longer life and better hole finish; will perform well in serial, repetitive drilling.
Selection of drill bit material + tip correction gives the biggest jump in quality at the same rpm and pressure.
Metal drilling technique for beginners
- Coolant (drilling oil/butter) extends life and improves edges.
- RPM: start slower, increase gradually; the harder the material or larger the diameter, set a lower RPM.
- Pressure: even, moderate; drill perpendicular to the material.
- Fix the workpiece in a vise/clamp - safety + repeatability.
Three common mistakes and our tips on how to solve them
- Material sliding → use C (split point) or E geometry with thin sheet; consider pre-scoring.
- Overheating and dulling → remember coolant and lower speeds; don't force pressure, don't use high speeds without necessity - they can affect overheating of the drill bit.
- Burr at sheet exit → E geometry or underpinning from underneath; reduce rpm before puncturing.
Sample SKUs from the GTX catalog
- HSS, DIN 338: GRAPHITE 54T980 / 54T981 - Small diameters, in accordance with DIN 338. great base for universal drilling.
- HSS, DIN 340 (elongated): GRAPHITE 54T994 / 54T925 - longer reach, reach through profile; remember lower RPMs and interruptions.
- HSS-Co (M35, cobalt): GRAPHITE 57H014, 57H026, 57H048-5 - higher heat resistance for stainless steel/harder steels; combine with 135° geometry.
- HSS TiN: GRAPHITE 54T950 (set) and 57H122 (single) - TiN coating = less friction and longer life.
In the GTX catalog you will also find a wide selection of HSS/HSS-G/HSS-CNC kits for professional tasks.
