1. The basic concept of drilling
In general, drilling refers to a processing method in which a drill bit is used to process holes on a product display. Generally speaking, when drilling a product on a drilling machine, the drill bit should complete two movements simultaneously: ① main movement, that is, the rotational movement of the drill bit around the axis (cutting movement); ② secondary movement, that is, the movement of the drill bit along the axis linear motion (feed motion) against the workpiece.
When drilling, due to the defects in the structure of the drill bit, it will leave traces on the processed parts of the product, affecting the processing quality of the workpiece, and the processing accuracy is generally below IT10 level, and the surface roughness is about Ra12.5μm, which belongs to the rough processing category. .
2. Operation process of drilling
1. Draw a line
Before drilling, first understand the requirements of the drawing. According to the basic standard requirements of drilling, use tools to draw the center line of the hole position. The center line must be clear and accurate, and the thinner the better, use a vernier caliper or steel ruler after marking the line Take measurements.
2. Draw a check box or check circle
After the line is marked and passed the inspection, an inspection square or inspection circle with the center line of the hole as the center of symmetry should be drawn as the inspection line during the test drilling, so as to check and correct the drilling orientation during drilling.
3. Proofing punch
After drawing the corresponding inspection square or inspection circle, you should make a sample punch carefully. Make a small point first, and measure several times in different directions of the cross center line to see if the punch is indeed punched on the intersection point of the cross center line, and then forcefully hit the sample punch straight, round, and big so that it can be accurately punched. Knife rest assured.
4. Clamping
Use a rag to clean the machine table, fixture surface, and workpiece datum surface, and then clamp the workpiece. The clamping is smooth and reliable according to the requirements, and it is convenient for query and measurement at any time. It is necessary to pay attention to the clamping method of the workpiece to prevent the workpiece from being deformed due to clamping.
5. Test drilling
Trial drilling must be done before official drilling: the chisel edge of the drill bit is aligned with the center of the hole to drill a shallow pit, and then visually inspect whether the orientation of the shallow pit is correct, and it is necessary to continuously correct the deviation so that the shallow pit is coaxial with the inspection circle. If the violation is small, the workpiece can be pushed to the opposite direction of the violation while pulling out the drill to achieve gradual correction.
6. Drilling
Machining drilling is generally based on manual feed operation, and drilling can be carried out after the azimuth accuracy of the test drilling is required. When feeding manually, the feeding force should not bend the drill bit to avoid skewing the axis of the hole.
3. A method with higher drilling accuracy
Sharpening the drill bit is the beginning of everything
The corresponding drill bit should be selected for sharpening before drilling. In addition to ensuring the correct top angle, relief angle, and chisel edge bevel angle, the length of the two main cutting edges is equal and symmetrical to the center line of the drill bit, and the two main flank surfaces are smooth, the sharpened drill bit is designed to facilitate centering and reduce the roughness of the hole wall. , The chisel edge and the main cutting edge should also be properly ground (preferably rough ground on a grinder first, and then finely ground on a whetstone).
Accurate marking is the basis
Use a height gauge to accurately mark the line, first of all, ensure that the alignment standard is accurate. When marking the line, make the stylus angle and the workpiece line plane form an angle of 40°~60° (along the line direction), so that the line drawn is clear and even. .
Pay attention to the selection of the datum plane for scribing, the datum plane must be processed accurately, and the flatness of itself and the perpendicularity to the adjacent surface must be guaranteed. After the cross line of the hole position is drawn, in order to ensure easy alignment when drilling, the center punch is used to punch out the center point on the cross line (the punch point should be small and the orientation should be accurate).
Correct clamping is the key
Usually, for holes with a diameter of less than 6mm, if the precision is not high, the workpiece can be clamped with pliers for drilling; for holes with a diameter of 6-10mm, if the workpiece is regular and flat, it can be clamped with flat-nose pliers, but the workpiece should be The surface is perpendicular to the spindle of the drill press. When drilling a hole with a larger diameter, the flat-nose pliers must be fixed with a bolt pressure plate; for larger workpieces with a diameter of more than 10mm, use the method of clamping the pressure plate to drill.
Accurate finding is the key
After the workpiece is clamped, don't rush to drop the drill, and the alignment should be carried out first.
There are static alignment and dynamic alignment. The so-called static alignment refers to the alignment before the drilling machine is started, so that the center line of the drilling machine spindle and the intersection point of the workpiece cross line are aligned. This method is safe and convenient for beginners, and is relatively easy to grasp, but because it does not consider the swing of the drilling machine spindle Uncertain factors such as drilling accuracy is low. Dynamic alignment is performed after the drilling machine is started. During the alignment, some uncertain factors are taken into account, and the accuracy is relatively high.
Careful inspection cannot be less
The detection can accurately and timely discover the precision of the hole, so that necessary measures can be taken to compensate.
For holes with high drilling precision, we generally use the processing technology of drilling, reaming and reaming. After drilling the small hole in the first step, use a caliper to detect the error offset from the center of the bottom hole to the reference plane, and convert the position between the bottom hole and the ideal center through actual measurement. If the error is not greater than 0.10mm, you can use it when expanding the hole. Appropriately increase the apex angle of the drill bit, weaken the automatic centering effect, and make compensation by properly pushing the workpiece in the positive direction and gradually increasing the diameter of the drill tip. If the error is greater than 0.10mm, the two side walls of the bottom hole can be trimmed with assorted round files, and the trimmed part should be connected with the arc of the bottom hole with a smooth transition.
