Tools that drill holes or expand existing holes on the solid material of the workpiece are collectively called hole processing tools, and hole processing tools are widely used in machining. Due to the different shapes, specifications, precision requirements and processing methods of holes, there are many types of hole processing tools. This article mainly introduces twist drills for machining holes in aluminum and cast iron.
Features of twist drills for aluminum and cast iron processing
118° apex angle design, suitable for processing short-chip materials such as cast iron and silicon-aluminum alloys.
The diameter of the blade is equal to the diameter of the shank, and it adopts a double-flat drill point design, which is easy to process and manufacture.
The spiral groove chip removal is smoother, the chip holding space is large, and the cutting edge strength is good.
Features of three-edged twist drill for machining aluminum and cast iron
Suitable for drilling solid workpieces such as cast iron and aluminum alloys.
Three-blade construction enables high feed rates and excellent centering capabilities.
High processing reliability, suitable for harsh working conditions.
The thickness of the drill core is large, generally 15% to 30% of the drill diameter, and the centering performance and guiding performance are good;
When drilling, the cutting is balanced, there is no shaking phenomenon, the machining accuracy is high, and the cylindricity, straightness, and surface roughness of the hole shape are greatly improved compared with ordinary twist drills.
Features of Straight Fluted Drills for Aluminum and Cast Iron Machining
It is suitable for short-chip materials such as cast iron and silicon-aluminum alloys.
Excellent self-centering ability, which can realize high-efficiency machining and obtain workpieces with hole machining accuracy up to H7.
The processed holes can achieve high position accuracy, straightness and surface finish.
Features of Spot Drill for Aluminum and Cast Iron Machining
It is suitable for drilling center holes and chamfering on CNC machine tools. There are two kinds of spot drills with 90° top angle and 120° top angle.
Compared with the general center drilling tool, the center drill is more stable, and it is very convenient to carry out the center drilling process on the inclined surface.
Recommended value of drilling feed in different working conditions
Drilling part surfaces with inclination angles up to 10° is acceptable when drilling inclined surfaces, the key is to reduce the feed at the entry to prevent the bit from slipping and on the bit exit to prevent margin wear and bit damage :
1) The inclination angle is less than 5°:
The cutting action is intermittent. Feed needs to be reduced to one-third of normal feed rate until all diameters are cut.
2) Through hole:
When the through hole is drilled, the feed must be reduced to 1/3 of the normal feed rate.
3) The inclination angle is 5-10°:
Start the centering operation or mill a facet with a short drill with the same point angle.
4) The inclination is greater than 10°:
Cannot be drilled unless the entire surface has been prepared.
B. Irregular surface:
When drilling, the feed must be reduced to a quarter of the normal feed rate to prevent chipping.
C. Concave surface:
Drilling is possible if the radius is greater than 15 times the drill diameter. When drilling, the feed must be reduced to one-third of the normal feed rate.
D. Convex surface:
If the radius is greater than 4 times the drill diameter and the hole is perpendicular to the surface. When drilling, the feed must be reduced to half the normal feed rate.
E. Cross hole drilling:
If drilling in and out of intersecting holes, the feed is reduced to a quarter of the normal feed rate.
F. Stack drilling:
Good clamping makes it possible to drill multi-layer boards in one pass with full feed: because boards are generally not perfectly straight. A common method is to place industrial paper (thickness about 0.5-1 mm) between the plates, which smoothes out irregularities and reduces vibrations.
