USE OF DRILLS AND CUTTING CONDITIONS

Stainless steel can be effectively drilled with cobalt drill. It is a drill made from steel containing besides other alloying elements also cobalt. To drill the stainless, 5 % cobalt alloy is appropriate (our code 07 and code 25 for long drills). Considering hard workability of stainless steel, it is essential to choose lower cutting speed (only 6-10 m/min which is, for example, for 5-milimetre-drill 380-635 r/min).

HARDOX is an abrasion-resistant material which is extremely tough and very hard workable. We recommend you to use either stable drill machine or CNC centre. We sell drills convenient for HARDOX 400, HARDOX 450 and HARDOX 500 under codes 10 (with taper shank) and 08 (with straight shank). These drills are made from steel containing 8 % cobalt, which enables them to endure extreme mechanical and thermal strain when working HARDOX. Choose low cutting speed rather than high (5-9 m/min; to see the details, click on the link at the end of the article: “Use of Drills and Cutting Conditions”). If the tip of the drill has already got through the other side of material, it is necessary to lower the level of machine feed or rather, to switch it off as finishing of drilling can cause chipping of the drill’s edge (finishing without reducing the feed causes a big impact).

In case of metal plates, the hole does not have to be deep. Thus, choose as short and tough drill as possible. We can offer you code 12: double-ended body drill which has self-centring point so it do not “dance” on the surface of material but gets into it immediately. Moreover, it has tips on both sides so in fact, you have two drills in one. To drill stainless and other hard-workable plates, you had best use drills with 5 % cobalt alloy, which is code 11—short drill—, also with self-centring point.

There are various types of steel which can be hardened more or less. So, you have to choose the drill according to the hardness of steel. If you need precise holes in steel hardened to 60 and more HRC, use solid carbide drills from either code 82 (without internal cooling) or code 83 (with internal cooling). These drills can be used only in machines with clearance of spindle - no more than hundredth of millimetre, so almost just in CNC and NC machines. If you want to drill into steel hardened to 40 HRC, you can use drills for metal with soldered-in plate: codes 80 (with straight shank) and 81 (with taper shank). Both of them are also suitable for drill press, and drills from code 80 even suits hand power drill and are quite cheap. If you do not have special requirements for the quality of the hole, you can use drills with soldered-in plate of the code 70 and 71 (named “All-round drills”) to drill even into very hard steel (more than 50 HRC). High revolutions are recommended: 2,000-3,000 r/min and very small hand feed. At the same time, it is essential not to let the drill overheat. Though a solder, which holds a cutting plate with the body of the drill, has melting temperature 1,100 ° C, it is rather easy to reach this temperature in high revolutions.

It is easy to drill soft wood with drills for wood with centring point and two edges, which is our code 30; the result is a smooth hole. When drilling into wood, it is important to lower feed or to push the drill less when the tip of the drill is close to reaching the other side of material. Then the hole will be smooth also on the other side of the object. If you do not lower feed or tension on the drill, wood surrounding the hole will be torn off, which looks unsightly and in many cases the object is not usable any longer. To have deeper holes, you can use auger bits “LEWIS”, which drill smooth holes throughout the profile of the hole. You have to take care of a good outlet of chips from the hole by pulling the drill out of the hole from time to time in order not to block the hole and the drill in it. If you lack drill for wood, it is possible to make the hole with a drill for metal but it is very important to lower the pressure when reaching the other side of material. Of course, the quality is lower than when using a drill made especially for wood. Important note on safety risk! Long drills, but the short ones as well, can drill through material surprisingly quickly and if there is somebody there, it can cause injury or even death!

Before you start drilling into concrete, you have to know what it is made from. In case of full brick, you can drill both with and without impact. When drilling with pneumatic impact, which has hammer drills and some power drills, it is very comfortable as the drill gets into material very easily without putting great force on the drill. You can use a drill with mechanical impact which moves the drill into concrete well, but you have to push harder. Drilling without impact is more strenuous for you, so in this case you will appreciate the quality of the drill best as a low-quality drill gets into concrete usually slowly and you have to push very hard, whereas a good drill gets into material well though you push less. To drill both with and without impact, you can use drills from our code 50.

Concrete from hollow bricks (for example Porotherm) has to be indispensably drilled without impact. If you drilled with impact, you would break internal dividers in the brick and its toughness would decrease, what could have fatal impact if you drilled more holes. Therefore, use a high-quality drill and work with constant pressure of your hands. If the wall is plastered and you do not know what it is made from, you can realise it when drilling the first hole. If you drill and after 2 centimetres the drill drops about 3 centimetres and after 1 centimetre there is another drop, it is almost certain that it is a hollow brick.

Drilling of reinforced concrete is not a big problem today if you use good drills with a suitable drill, or rather, hammer drill. A good drill, though if it encounters iron bar, finishes drilling without losing its straight direction. A bad drill is either damaged or loses straight direction of drilling when contacting iron. The best is hammer drill with pneumatic impact because drilling with hand power drill with mechanical impact or without it is quite strenuous. We offer you high-quality drills under the code 60 for drilling with hammer drills with SDS-plus clamping, and under the code 61 for machines with SDS-max clamping.

Use core bit to drill big-diameter holes into concrete and masonry, for example holes for electrical boxes and big diameters of pipes. Core bit has more resistance, thus hammer drill with high power and electro-pneumatic impact is appropriate. But watch out: you must not use impact when drilling into walls made from hollow bricks! These hammer drills have either SDS-plus or SDS-max clamping. You can find core bits with SDS-plus clamping at the end of the “Drills for Concrete SDS-plus” section, and with SDS-max clamping at the end of the “Drills for Concrete SDS-max” section.