What do counterbore and leveling mean in mechanical drawing? Who can elaborate?

Generally speaking, reaming refers to machining holes. Generally, the countersunk hole plane or countersunk hole is used to make the slab surface flush with the countersunk hole, and the countersunk hole is used as the plane for bolt connection. For the cast boss, generally use the lead-out label: until it is flat, the size is not marked. Counterbore or countersink is used to indicate counterbore or air interface plane. Generally speaking, leveling refers to machining holes.

In fact, this is a concave step for connecting the smoothness of the surface with the sinking of the nut. Usually the nut is exposed outside the connection surface, but sometimes it needs to sink to make the nut as flat as the outer surface.

Countersunk hole: drill a hole so that the screw head can be hidden in the workpiece, that is, deposits can pass through this hole.

Countersunk hole: Countersunk hole can make the nut of mounting bolt lower than the plane, but not protrude from the plane.

Extended data

The countersinking method and drilling method are basically the same. The main problem of reaming is that vibration marks are produced on the end face or conical surface of counterbore due to the vibration of cutter. The vibration marks are especially serious when the twist drill is modified into countersunk drill. In order to avoid this phenomenon, the following points should be paid attention to when drilling.

(1) The cutting speed of counterbore should be lower than that of drilling, which is generally 1/2 ~ 1/3 of the drilling cutting speed. At the same time, due to the small axial resistance during reaming, the hand-feeding pressure should not be too large and should be uniform. In precision reaming, the inertia of the spindle after the drilling machine stops is often used to reaming to reduce vibration and obtain a smooth surface.

(2) When reaming, the feed rate is 2-3 times that of drilling, because the cutting area of reaming is small, the number of cutting edges of standard reaming is large, and the cutting is smooth.

(3) Try to grind the countersink with a shorter bit, pay attention to grinding the front face, reduce the rake angle, and prevent the cutter from sticking and vibration. When grinding a countersunk drill with a twist drill, it is necessary to ensure that the two cutting edges have the same height, symmetrical angles and smooth cutting. The back angle and front angle at the outer edge should be reduced appropriately, and the smaller back angle should be selected to prevent polygons, so as to reduce vibration and prevent knife stab. At the same time, after grinding on the grinding wheel, it is polished with oilstone to make the cutting even and smooth and reduce the vibration during machining.

(4) The arbor and blade of counterbore shall be well matched, firmly clamped and reliably guided, and the workpiece shall be compacted, and there shall be no vibration during counterbore.

(5) Before clamping the workpiece, adjust the coaxiality of the bolt through hole and the countersink of the workpiece. During adjustment, the spindle can be rotated for trial drilling, so that the workpiece can be positioned naturally. The workpiece should be clamped to reduce vibration.

(6) In order to control the depth of counterbore, before counterbore, the depth ruler and positioning nut on the drilling machine can be used to adjust and position the feed depth of the main shaft (counterbore drill) of the drilling machine.

(7) When polygonal vibration lines appear on the surface of countersunk head, the machining shall be stopped immediately, and problems such as sharpening of drill bit shall be found and corrected in time.

(8) When cutting steel parts, due to the high cutting heat, lubricating oil should be added to guide posts and cutting surfaces.

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