1. Grinding the drill well is the premise
Before drilling, the corresponding drill bit should be selected for sharpening. In addition to the correct top angle, back angle and transverse edge bevel angle, the length of the two main cutting edges is equal and symmetrical with the center line of the drill bit, and the two main back blade surfaces are smooth, in order to facilitate centering and reducing the roughness of the small hole wall, proper grinding should be done for the transverse edge and the main cutting edge.
2. Accurate scribing is the basis
With height ruler accurate scribing, first of all, the correct size should be kept accurate. When scribing, an angle of 40~60 degrees should be formed between the scratch awl angle and the scribing plane of the workpiece to make the scribing lines clear and even. Attention should be paid to the selection of scribing datum plane. The datum plane should be processed accurately to ensure its flatness and verticality with adjacent surfaces. After the hole position Cross curve is drawn out, in order to ensure that it is convenient to find the correct position during drilling, the center punch is applied to punch out the center point on the cross curve.
3. Correct clamping is the key
Under normal circumstances, for holes with a diameter less than 6mm, if the precision is not high, pliers clamping workpiece can be used for drilling; For holes with a diameter of 6~10mm, if the workpiece is regular, flat-nose pliers clamping can be used, however, the surface of the workpiece should be perpendicular to the spindle of the drilling machine. When drilling a hole with a larger diameter, the flat-nose pliers must be fixed with a bolt press plate; When the hole diameter is more than 10mm, the pressure plate clamping method is applied to drill the hole.
4. Accurate search is the key point
After the workpiece is installed and clamped, do not rush to drop the drill, and correct it first. There is static correction and dynamic correction. The so-called static alignment refers to the alignment before the drilling machine starts, so that the center line of the drilling machine spindle and the intersection point of the workpiece cross curve are aligned. This method is safe and convenient for beginners and easy to master, however, the drilling accuracy is low because uncertain factors such as the swing of the drilling machine spindle are not considered. Dynamic search is exactly after the drilling machine is started to find the correct. While finding the correct, some uncertain factors are taken into account, and the precision is relatively high.
5. Careful detection is indispensable
Detection can accurately and timely find the accuracy of holes, so as to take necessary measures to remedy. For holes with high drilling precision, we generally adopt the processing technology of drilling, reaming and reaming. After drilling the hole in the first step, use caliper to detect the error offset from the center of the bottom hole to the base plane, and calculate the position of the bottom hole and the ideal center through actual measurement. If the error is not more than 0.10mm, during reaming, the top angle of the drill bit can be appropriately increased, the automatic centering effect can be weakened, the workpiece can be appropriately pushed to the right side, and the diameter of the drill tip can be gradually plus-sized to remedy. If the error is greater than 0.10mm, assorted round rasp can be used to trim the wall on both sides of the bottom hole, and the trimming part should be connected with the arc smooth transition of the bottom hole.
