Which drill bit is suitable for drilling in Hardox?
Drilling holes in Hardox (300, 400 and 500) is a challenge, but certainly not impossible with the right tools and respect for the properties of the material. Usually these are through holes in wear plates or wear parts of machines where normal steel is subject to extreme wear. Cobalt drills or CDX drills offer a good solution for drilling in Hardox.
Drilling method in Hardox
Hardox is self-hardening. This means that the heat developed during the drilling process ensures that the wall of the hole is hardened. That is why the cooling is an important factor when drilling in Hardox. An abundant amount of coolant or emulsion cools both the workpiece and the tool and is a requirement for the smoothest possible drilling process. In addition, it is also recommended with Hardox to drill the hole to depth in one go. Resuming an interrupted drilling process is very difficult, given the self-hardening properties. Restarting a drill in a (partly) hardened hole is disastrous and causes enormous wear
Choice of drill
There are several types of drills that work well in Hardox. As is often the case, solid carbide drills with internal cooling on a CNC machine are the most efficient solution. Significant tool life can also be achieved with this. But a CNC machine is not always available. In that case, you can opt for an HSCo cobalt drill. Most cobalt drills in the Dormer Pramet range have a cobalt content of 8%.
Solid carbide drills
Without internal cooling:
- R520 : This CDX drill has a convex cutting edge and a thick core for extra strength. This makes this drill optimal for use in both CNC and hand-operated machines that do not have internal cooling. The dimensions are according to the short DIN 6539 version. The top angle is 130 degrees. These drills are available from 3.0mm to 16.50mm.
- R510 : Same drill as above but in a longer DIN 338 version. Available from 3.0mm to 14.25mm.
With internal cooling:
- R457 : This Force X drill is used on CNC machines with internal cooling. The dimensions are according to the short version DIN 6537 – 3xD. The apex angle is 140 degrees. Available from 3.0mm to 20.0mm.
- R453 : Same as above, only according to the longer version DIN 6537 – 5xD. Available from 3.0mm to 20.0mm.
Kobaltboren (HSCo of HSS-E)
- A117 : Short HSCo drill (8% cobalt content) according to DIN 1897 with a top angle of 135 degrees. Available from 2.50 mm to 13.00 mm.
- A777 : Normal HSCo boron (8% cobalt content) according to DIN 338 with a top angle of 135 degrees. Available from 0.30 mm to 16.0 mm.
- A730 : Morse taper HSCo drill (8% cobalt content) according to DIN 345 with a top angle of 118 degrees. Available from 10.00 mm to 32.00 mm
Tips and recommendations when drilling in Hardox
- During drilling, supply the process liberally with emulsion or abundant coolant, because the material is self-hardening. Any heat released during drilling can harden the material.
- The desired pressure of the internal cooling is about 20 bar. Less is also possible, but then the cutting data must be adjusted downwards.
- Use the correct machining conditions appropriate to the circumstances.
- Ensure a stable machining process – due to the toughness of the material it is important to minimize vibrations. Therefore choose the shortest possible drill bit, keep the distance between drill bit and holder as small as possible and also ensure that the workpiece is clamped firmly.
- Drill the hole in a smooth, non-stop motion.
- Hardox should preferably never be pre-drilled, only lightly center with the correct top angle.
- Observe your safety and that of others and use the required protective equipment.
Below are all drills that are suitable for Hardox:
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