VÖLKEL HexDrive TwinBox: From Tap Drill Hole to Finished Thread
The quality of an internal thread begins with the tap drill hole. That is why the new VÖLKEL HexDrive TwinBox pairs an HSSE twist drill for drilling the hole with the matching HSSE machine tap for the same thread size. Both tools have the same 1/4" hex drive (HexDrive).
TwinBoxes are available for thread sizes M3, M4, M5, M6, M8, M10 and M12. Depending on the application, you can choose Form B for through holes or Form C with a 15° right-hand spiral flute for blind holes.
Simon Siebert, Head of Production and Quality Assurance at VÖLKEL:
“If the tap drill hole is too small, the tap is subjected to unnecessary stress and can break as soon as it enters the hole. If the hole is too large, the load-bearing capacity of the finished thread drops significantly.”
What is inside the HexDrive TwinBox?
Each TwinBox is dedicated to one thread size. It contains exactly the two tools needed to produce the internal thread: the matching twist drill for the tap drill hole and the machine tap for cutting the thread.
For example, the M6 TwinBox contains a 5.0 mm twist drill and an M6 machine tap. For M10, it contains an 8.5 mm twist drill and the corresponding M10 tap.
| Thread | Tap drill Ø | Item no. Form B | Item no. Form C, 15° right-hand spiral flute |
|---|---|---|---|
| M3 | 2.5 mm | 37580 | 37680 |
| M4 | 3.3 mm | 37581 | 37681 |
| M5 | 4.2 mm | 37582 | 37682 |
| M6 | 5.0 mm | 37583 | 37683 |
| M8 | 6.8 mm | 37584 | 37684 |
| M10 | 8.5 mm | 37585 | 37685 |
| M12 | 10.2 mm | 37586 | 37686 |
These versions are designed for metric ISO threads to DIN 13. The taps have an ISO 2 / 6H tolerance.
If you need several common sizes rather than individual sizes, the same tool concept is also available as a HexDrive set. It brings together M3, M4, M5, M6, M8, M10 and M12 with their matching twist drills in one case, but the complete set comes in just one version: either Form B for through holes or Form C with a 15° right-hand spiral flute for blind holes. With TwinBoxes, you choose the version separately for each thread size. For example, you can combine an M8 Form B TwinBox with an M8 Form C TwinBox when you cut both through-hole and blind-hole threads in that size.
Why do the twist drill and machine tap share the same HexDrive?
The common 1/4" hex drive is the key feature of the system. The twist drill and machine tap can be used with the same tool holder. Once the tap drill hole is drilled, you change only the tool, not the holder. The sequence is straightforward: drill the hole, change tools, cut the thread.
HexDrive tools can be used on a stationary drill press or with a handheld drill, either in a three-jaw chuck or with a bit adapter. With a bit adapter, the HexDrive machine tap offers a particular advantage: it combines the flexibility of a bit with the geometry and cutting performance of a full-size machine tap.
The two operations also stay together in the workshop. The twist drill and tap are stored in the same TwinBox. You do not have to pick out the matching diameter from a larger assortment, reducing the risk of accidentally using the wrong tap drill size. Put both tools back in their box after use and the pairing remains clear for the next job.
For more on the HexDrive system, see our article on the HexDrive Limited Edition M3–M12.
Form B or Form C: Which TwinBox suits the job?
There are two TwinBox versions for through holes and blind holes.
Form B with a spiral point is intended for through holes: its point pushes chips ahead of the tool in the cutting direction so they exit through the open end. Form C with a 15° right-hand spiral flute is designed for blind holes: the flute carries chips up and out of the hole. For a blind hole, drill the tap drill hole deeper than the required thread depth because the threads in the tap's lead do not yet form a full profile.
Important: The designation Form C appears in two different contexts in the TwinBox. For the machine tap, Form C identifies the version for blind holes. On the twist drill, “Form C point” refers instead to the split point to DIN 1412. These names describe different tool features.
Our comparison explains in more detail why the two geometries handle chips differently and what else matters when choosing a tap.
What applications is the HexDrive TwinBox designed for?
The HexDrive TwinBox is intended for general use in readily machinable materials up to 900 N/mm², including unalloyed and low-alloy steels. The machine taps are made of HSSE. The twist drill is a Type N HSSE-VAP version. It is profile-ground, meaning its geometry is fully ground. This provides accurate concentricity and a consistent diameter, creating a sound basis for a tap drill hole of the correct size.
The TwinBox is particularly useful if you regularly work with a few fixed thread sizes. Consider assembly work where M6 and M10 threads are the main requirements: take those two TwinBoxes with you. For each size, the twist drill and tap are already paired in their own box. Instead of carrying a complete assortment, you have the tool pairs needed for the work ahead.
The same principle works at fixed workstations. If the same thread sizes are produced repeatedly, the relevant TwinBoxes can be kept within reach without selecting tools from a larger assortment each time.
The TwinBox does not replace a complete tap assortment. It brings together exactly the tool pairs you need for your application.
HexDrive TwinBox at a glance
- Contents:
- 1 HexDrive machine tap + 1 matching HexDrive tap drill
- Thread sizes:
- M3, M4, M5, M6, M8, M10, M12; metric ISO threads to DIN 13
- Versions:
- Form B with spiral point for through holes or Form C with 15° right-hand spiral flute for blind holes
- Machine tap:
- HSSE, ISO 2 / 6H tolerance, design based on DIN 371 / DIN 376
- Tap drill:
- HSSE-VAP, Type N, Form C point (split point to DIN 1412; distinct from the machine tap's Form C blind-hole design), profile-ground, 2.5 to 10.2 mm
- Drive:
- common 1/4" hex drive (HexDrive)
- Materials:
- readily machinable unalloyed and low-alloy steels up to 900 N/mm²
- Item numbers:
- 37580–37586 (Form B), 37680–37686 (Form C)
Need a different thread size?
The TwinBoxes cover metric ISO coarse threads from M3 to M12, each with its matching twist drill. Fine threads, sizes outside this range and other thread systems such as inch threads are not included.
You can use our interactive tap drill calculator to find the appropriate hole diameter for other threads.
👉 Calculate the tap drill diameter
Would you like to use a twist drill and tap as a matched pair?
