Definition and classification of drilling machines
Drilling is a commonly used tool in production and processing. Thanks to the popularity of handheld drills, it is also the easiest to understand. A drilling machine refers to a machine tool that mainly uses a drill bit to process holes on a workpiece; usually the drill bit rotates as the main motion, and the drill bit moves axially as the feed motion for processing, and the workpiece does not move during the processing.
Drilling machines can drill through holes and blind holes; when supplemented by special tools, they can also achieve expansion, countersinking, reaming or tapping. It is an indispensable general-purpose machine tool for mechanical manufacturing and various repair factories.
Depending on the size, structure and production batch of the workpiece, drilling machines can be divided into bench drilling machines, vertical drilling machines, radial drilling machines, etc.
Bench drilling machines are the most commonly used small drilling machines, generally used to process holes with a diameter of less than 13mm. It is driven by an electric motor and a V-belt to drive the spindle of the drilling machine to rotate; by changing the position of the V-belt on the tower pulley, different rotation speeds can be obtained.
Bench drilling machines generally use straight shank drill bits, which are clamped by drill chucks. The feed motion is mostly controlled manually, and there is no automatic feed. Therefore, bench drilling is simple and flexible, with low processing precision, and is suitable for hole processing with low requirements.
Hole larger than 13mm or with higher requirements should be processed by a vertical drilling machine. The vertical drilling machine is composed of an electric motor, which changes the speed through a gearbox and transmits the motion to the spindle. Changing the position of the speed change handle can get different speeds, and changing the position of the feed handle can get different feed amounts.
Vertical drilling machines use taper shank drill bits. The taper shank is manufactured according to the Morse taper standard and is divided into 7 specifications from No. 0 to No. 6. Only taper holes and taper shanks with the same number can be used together. When the number of the drill taper shank is smaller than the number of the taper hole of the drilling machine spindle, a transition taper sleeve should be used in the middle to connect them. The drill taper shank and the transition taper sleeve have flat tails at the end, which can be disassembled with an oblique plug iron.
Like the benchtop drilling machine, the vertical drilling machine uses the method of moving the workpiece to align the hole to be processed with the axis of the drilling machine spindle for processing.
For large workpieces, a radial drilling machine is used for processing. When the radial drilling machine is used for processing, the workpiece is placed on a floor-standing workbench or on the ground. The rocker arm can rotate on the column, or it can rise or fall along the column. The spindle box can move along the horizontal guide rail of the rocker arm, so that the spindle position can be adjusted to align with the axis of the hole at various positions on the surface of the workpiece for processing.
The spindle box of the radial drilling machine is driven by an electric motor, which can change both the speed and the feed rate; generally, a quick-change drill chuck is used to clamp the tool, which is very convenient to operate.
Three major processing processes of holes
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01 Drilling
The expansion of the hole drilled by the drilling machine is unstable, the dimensional accuracy is not high, the hole wall is easily scratched by chips, the axis is easily deflected and bent, and the surface roughness value is large. Therefore, the holes drilled directly by the drill bit are only suitable for unimportant places, such as the through holes of fasteners, which can be used directly after drilling.
For more important holes, it is necessary to leave appropriate processing allowances before the subsequent expansion and reaming.
02 Expansion
Expansion is a processing method that uses a reamer to expand the pre-made hole. The appearance of the reamer is somewhat similar to that of the twist drill, but the reamer has more blades than the twist drill, the core diameter is relatively large, the knife is good and there is no cross edge, and the processing allowance is smaller than the drill bit, so reaming can correct the shape error and position error of the prefabricated hole, and the processing accuracy is improved compared to drilling.
03 Reaming
After reaming, it is generally necessary to reame. Reaming is a processing method for finishing with a reamer. The number of teeth of the reamer is more than that of the reamer, and the processing allowance of reaming is much smaller than that of reaming. The cutting thickness is very thin, the tool rigidity is good, and the cutting speed is low. It can well polish the hole wall, calibrate the hole diameter, and correct the roundness and straightness errors of the hole.
However, the position of the hole must be guaranteed by the drill jig or the previous process. Reaming cannot correct the position error of the hole and the deflection of the axis. For small-sized holes with high precision requirements, the most commonly used typical processing process is to drill first, then expand the hole, and finally ream the hole.
If you want to know more about drilling machines, please contact Shanghai ANTISHI Machine Equipment Co., Ltd. We provide customers with timely technical support, training and high-quality, precision processing machine tools.
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