Helix angle γ: Different models have different angles, generally 10°~40°.
Margin: mainly plays the role of guiding and extrusion.
Back: The part between the land and the groove, but lower than the land, reducing the cutting force (friction).
Chip flute surface: Sometimes it is the rake face, where the chips flow.
Drill tip angle: the intersection of the land and the cutting edge.
Main cutting edge: The included angle between the two main cutting edges is the apex angle б, the real cutting part.
Flank face: the face that forms the clearance angle α.
Chisel edge: the part connecting the two cutting wedges, it bears 50% of the cutting force (axial).
Back clearance: reduce the friction between the drill and the workpiece.
Chip flute: larger space for chip removal.
Orifice notch and burr problem?
Improvements can be made by reducing the tip angle so that the tip meets the width and height of the workpiece.
Smaller drill point angle 118°
1. Radial component force and poor radial stability.
2. Small axial force.
3. Non-ductile material to reduce collapse.
Larger drill point angle 135°~140°
1. Large axial separation and good radial stability.
2. Greater feeding capacity.
3. Soft viscous material to reduce flash.
4. The roundness, diameter tolerance, and straightness of the hole are better.
Peripheral chamfered drill point
1. Reduce the collapse.
2. It has the advantage of a large drill point angle drill bit.
Drill application problems/measures
Drill tip wear
reason:
1. Under the action of the drilling force of the drill bit, the workpiece will move down, and the drill bit will bounce back after drilling through.
2. The rigidity of the machine tool is insufficient.
3. The drill material is not strong enough.
4. The drill bit jumps too much.
5. The clamping rigidity is not enough, and the drill bit slides.
measure:
1. Reduce the cutting speed;
2. Increase the feed rate;
3. Adjust the cooling direction (internal cooling);
4. Add a chamfer;
5. Check and adjust the coaxiality of the drill bit;
6. Check whether the rear angle is reasonable.
Chipped, Broken
reason:
1. The vibration of the drill bit is caused by the excessive impact on one cutting edge.
2. The clamping rigidity of the workpiece is low, which occurs when the hole is cut out.
3. The feed rate is too large.
4. The cutting speed is too high.
measure:
1. Adjust the vibration of the installation to be less than 0.02mm, so that the two edges of the drill can be drilled under balanced conditions.
2. Reduce the feed rate to reduce the impact of the drill bit when cutting out.
3. If it is an indexable drill, change the insert material.
Accumulation of tumor
reason:
1. Caused by the chemical reaction between the cutting material and the workpiece material (low carbon steel with higher carbon content).
measure:
1. Improve lubricant, increase oil or additive content.
2. Increase the cutting speed and reduce the feed rate to reduce the contact time.
3. If drilling aluminum, use a polished, uncoated drill.
Broken tool
reason:
1. The helical groove of the drill bit is blocked by chips, and the cutting is not discharged in time.
2. When the hole is drilled quickly (drilling through), the feed rate is not reduced or the machine is changed to manual feed.
3. When drilling soft metals such as brass, the back angle of the drill bit is too large, and the front angle is not ground, so that the drill bit is automatically screwed in.
4. The grinding of the drill blade is too sharp, resulting in the phenomenon of chipping, and the tool cannot be retracted quickly.
measure:
1. Shorten the cycle of tool replacement.
2. Improve the installation and fixation, such as increasing the support area and increasing the clamping force.
3. Check the spindle bearings and sliding grooves.
4. Use high-precision tool holders, such as hydraulic tool holders.
5. Use tougher materials.
