Drilling: Depth and Diameter Control Techniques

1. Drilling Depth Control
Drilling depth control is an important part of drilling processing. Too deep drilling may lead to material waste or increased processing difficulty, while too shallow drilling cannot meet the design requirements. The following are several commonly used drilling depth control methods:
Use depth scale or stopper:
Install a depth scale or stopper on the drilling machine, and set the drilling depth by adjusting the position of the scale or stopper. This method is simple and intuitive, and is suitable for drilling depth control in mass production.
Measure the actual size:
During the drilling process, use tools such as vernier calipers or depth gauges to measure the depth of the drilled hole, and adjust the drilling depth according to the measurement results. This method is suitable for occasions with high requirements for drilling depth.
Use the shoulder of the drill bit:
Some specially designed drill bits have a shoulder on the drill shank. When the drill bit drills into the workpiece to a predetermined depth, the shoulder will contact the surface of the workpiece, thereby limiting the further feed of the drill bit. This method requires the  drill cutterbit to have a special shoulder design.
Programming control of CNC drilling machines:
On CNC drilling machines, the depth of drilling can be set by programming. CNC drilling machines will automatically adjust the drilling depth according to the preset program to achieve precise control.
2. Control of drilling diameter
Control of drilling diameter is equally important, which directly affects the dimensional accuracy and assembly performance of the processed parts. The following are several commonly used methods for controlling drilling diameter:
Choose a suitable drill bit:
Choose a suitable drill bit diameter according to the hardness and thickness of the processed material. A drill bit diameter that is too small may lead to low processing efficiency, while a drill bit diameter that is too large may damage the workpiece or the drill bit.
Pre-drilling center hole:
Before formal drilling, pre-drill a shallow center hole with a small diameter drill bit. This helps guide the large diameter drill bit and prevent deviation, thereby improving the diameter accuracy of the drilled hole.
Control drilling speed and feed rate:
Reasonable drilling speed and feed rate are crucial to controlling the drilling diameter. Too fast drilling speed may cause the drill bit to overheat or damage, while too large a feed rate may cause the drilling diameter to be too large. Therefore, the appropriate drilling speed and feed rate should be selected according to the processing material and drill type.
Use cutting fluid:
Using cutting fluid during drilling can reduce cutting temperature and reduce drill wear, thereby improving the diameter accuracy of the drilled hole. At the same time, the cutting fluid can also play a role in lubrication and cooling, which helps to extend the service life of the drill.
Regularly check and sharpen the drill:
The drill will gradually wear during use, resulting in a larger diameter of the drilled hole. Therefore, the drill should be checked and sharpened regularly to ensure its sharpness and diameter accuracy.
3. Precautions during drilling
Keep the drill stable:
During the drilling process, the drill should be kept stable to avoid shaking or offset. This can be achieved by using auxiliary tools such as fixtures or guide rails.
Timely chip removal:
A large amount of chips will be generated during the drilling process, which should be cleaned in time to avoid clogging the drill or affecting the quality of drilling. For deep hole drilling, intermittent feed or retracting can be used to remove chips.
Pay attention to safe operation:
When using a drill to drill, you should strictly follow the safe operating procedures and wear appropriate personal protective equipment, such as safety glasses, dust masks and gloves.