In this video we look at the basics of drilling, reaming, countersinking and threading metal. Before drilling, the center of the hole is marked on the workpiece with a scriber and punched with a punch. This centers the drill and prevents it from getting lost when it is started. When drilling into solid material, a hole is made in one operation. For large diameters, this requires a high feed force because the chisel edge only scrapes. In these cases, a smaller drill is used to pre-drill and then ream out to the finished size (called reaming). When profile drilling, conical or stepped shapes are created (center holes in a turned part). High-speed steel or hard metal are usually used as the material for twist drills and can have special coatings (increase service life). HM tools allow higher cutting speeds than HSS drills, but are more sensitive to impact loads. Conventional twist drills consist of a shaft and two spiral flutes that are connected to the drill tip via a cross cutting edge. The chip removal and the supply of cooling lubricant are carried out via the flutes. The two main cutting edges on the drill tip perform the main machining work. The main clearance surfaces are connected to the cross cutting edge and are slightly relief ground (clearance angle). The side cutting edges on the circumference are called secondary cutting edges and are provided with a guide chamfer. The strength of the spiral of the flutes is described by the helix angle (side rake angle). The smaller the side rake angle (lower the helix), the larger the wedge angle and the more stable the cutting edge. Twist drills with a low helix are therefore used for machining hard materials. These drill types are referred to as type H. The drill types N and W therefore have a stronger helix. These are used for drilling medium-hard or soft materials. When cutting an internal thread, the core hole is drilled with a conventional twist drill. The internal thread is then cut into this using a thread cutter. A special thread cutting device is used for machine thread cutting. Straight-fluted taps are often used for short-breaking chips. These are particularly suitable for through holes or for blind holes that are not too deep. For deeper blind holes, taps with right-handed grooves are used, which transport the chips upwards. Left-handed spiral grooves transport the chips downwards and are only suitable for through holes. When threading manually, the thread is usually produced in 3 steps (pre-cutter - middle cutter - finishing cutter). If an external thread is to be cut instead of an internal thread, dies are used. Before cutting an external thread, the cylindrical workpiece must have a certain external diameter that is slightly smaller than the nominal size of the thread. Countersinking is used on existing holes. Countersinking is used to produce a flat surface that protrudes from the workpiece (support surface for screw heads). To countersink the entire screw head, countersinking is used. It creates an additional cylindrical shape at the top of the hole. To countersink conical screw heads, profile countersinking is used. This creates a conical recess for the screw head. Profile countersinking with a countersink is usually also used for simple deburring of the edge of the hole or for countersinking the core hole for internal threads. The feed rate and cutting speed are significantly lower when countersinking than when drilling. Holes made with twist drills generally have a relatively poor surface quality and dimensional accuracy. For fits with high dimensional accuracy, shape accuracy and surface quality, the holes must therefore be reworked with a reamer. Reaming is essentially a type of reaming with low chip removal. Reamers usually have an even number of cutting edges, but these are not evenly divided around the circumference. This is intended to prevent vibrations and thus the formation of chatter marks on the reamed hole surface. 00:00 Marking and punching 00:47 Drilling into solid material 01:17 Boring 01:47 Profile drilling 02:05 HSS drills vs carbide drills 02:50 Structure (main cutting edge, cross cutting edge, helix angle) 04:47 Tapping (machine taps) 05:40 Chip grooves in taps 06:53 Thread cutting (hand thread cutter, tap wrench) 08:48 External threads (die cutting dies) 09:53 Thread specifications in technical drawings 10:46 Countersinking 11:59 Reaming 13:25 Structure of reamers (unequal pitch, chatter marks)