Drill sharpening

When sharpening drill bits, special attention should be paid to the angle at the vertex, axis rear angle, length of the transverse cutting edge back taper and the front corner of Potocki transverse cutting edge.

the Thickness a and width b of the cut when drilling


Liane of the apex angle 2φ of the drill when grinding is caused by the change of thickness a and width b of the cut when drilling with increasing angle 2φ, increased thickness and reduced width of cut.

the Back angle α is an important design element of the drill to which you should pay attention when sharpening drill bits. Its magnitude has a significant impact on the work of the friction forces and, consequently, the temperature in the cutting zone. When the temperature in the cutting zone of the processed material begins to actively absorb atmospheric gases, resulting in higher strength and lower ductility by altering the cutting process and the resulting inhomogeneity of the surface quality. The increase in the angle α when sharpening drill bits reduces friction, but reduces the rigidity, which leads to vibration of the drill and reduce the accuracy of the drilling.

clearance angle

Rear angle on top of drill bits for metal forming on the machine for sharpening of drills conical or plane sharpening. Stocktake when the conical surface is a smooth decrease in the rear corner. With a dual plane sharpening of the drill point are ground to a straight plane, to reduce the friction of the rear surface when drilling on the surface additionally remove a layer of material at an angle of 20-25°.

Bevel sharpening and sharpening the two-plane rear surface of the drill point

Transverse cutting edge

Transverse cutting edge worsens the process of penetration of the drill into the detail so its length reduces with the help of Potocki on the machine when sharpening drill bits. Reduce the length of the transverse cutting edge reduces the axial component of force by 25% compared to a drill without Potocki. Excessive decrease in the length of the transverse cutting edge leads to an increase in vibrations of the drill during cutting. The gun nose of the transverse cutting edges of drills can be of four types.

Shape Potocki transverse cutting edge:form A, form b, form C, circular gun nose

Form of Potocki

When you gun nose form A transverse cutting edge is undermined when sharpening drill circle with the formation of the concave curved surface. The gun nose shape In allows to undermine a transverse cutting edge with the grinding of the front surface along the straight path, aligning a cutting edge of the drill. The gun nose shape With saps transverse cutting edge with the outlet at an angle to the front surface of the tool. Circular gun nose undermines the transverse cutting edge with the formation of a convex curved surface.

angle

twist drill bit has a small amount of the front angle γ in points at the transverse cutting edge, which impairs the cutting process, the Central part of the drill. Allows the gun nose to the front corner of the transverse cutting edge. Excessive increase in the angle γ larger than the angle of inclination of the helical grooves, increases narezanie surface Potocki the front surface of the drill forming a hole with radius R. The hole prevents a descent chip and contributes to its sticking to the surface of Potocki that leads to a reduction in processing accuracy when cutting.

 the Formation of holes when sharpening drill bits with rake angle of Potocki more than the front groove angle

Machine for sharpening drills

Drill begins to wear out from the periphery of the cutting edge, due to the fact that on the periphery of the tool cutting speed is much more than the tip, so there is a maximum temperature, and heat when drilling from the corner cutting edge is difficult. Then abrade the rear surface of the tip of the drill. On the rear surface of the risks coming from the cutting edge. When wear of the drill, the risks are merged into one continuous strip along the entire cutting edge. As soon as possible to begin the process of regrinding the drill to the grinding machine to reduce the removable layer, and extend the life of the tool. When sharpening is necessary as to follow the shape of the sharpening of drill bits to maintain the desired cutting properties after sharpening.

model sharpening machine drills


drill Sharpening can be performed manually on the emery or grinding machine.

Machines for sharpening drills, no matter the material are domestic and industrial. Domestic grinding machines is quite compact and well suited for home work.

industrial machine for grinding drills, you can do the following

Surgery performed on the industrial machine for sharpening drills

suitable For home machines for sharpening drill bits the type of Drill Doctor and its Chinese counterparts. Basic sharpening drill bits on the machine is accurate alignment of the axis of the drill in the Chuck.

I Think you need to clarify that a fine drill bit with a diameter of 2-3 mm is good to sharpen fails because the accuracy of the machine not designed for it. In this case, you will need a special machine.

don’t forget that the cutting material of the drill does not tolerate overheating. When regrinding solid carbide materials crack, and high speed lose their hardness. When regrinding on the grinding machine need often to cool the drill with water or air, if the drill was steaming better it cool slightly at room temperature.

All of the machine for sharpening drills have design

the Main part of the machine for sharpening of drills consists of a fixed base and a removable tool holder with holes for drills of different diameter.

a Device for sharpening drill bits: 1 - rail; 2 - auger; 3 - emery wheel; 4 - base; 5 - holder
To the base at an angle of 30-32 degrees (angle dependent on the angle of drill point) is attached to the rail with a beveled side face with a 25-30° angle. The rail guides to the desired angle tool holder with sharpening drill relative to the grinding wheel. One of the sidewalls of the holder has an angle of 60-65°. The sidewall of the tool holder is pressed against the rail at the base that provides the front sharpening angle of the drill with the desired geometrical parameters on the machine for sharpening drills.

Please note that the cutting edges after sharpening on the drill sharpening machine drill length should be equal, and inclined at the same angle to the drill axis. The size of the transverse cutting edge at the correct sharpening of the drill in the machine should not be exceed 0.5 mm for drills with diameter less than 8 mm, if more it needs to be up to 1.4 mm.

drill Sharpening on the machine BSM 20

Sharpening drill bits

Hold the drill with the screw. Lightly grip the drill, it must turn in the prism. Now install the main cutting edge drill in the direction of shown in the figure. With the screw-tighten the lens.

prism is clamped in it with the drill mounted to the stand mount of the prism and clamped and screw. Scale is set right angle drill (standard 118° angle) Desk clamped arm.

-left scale: the stand is given to the left
-right scale: the stand is given to the right

by feeding the prism and flow of the engine position the drill before grinding around. Carefully setting the flow of the prism, at the same time turn it and sharpen the first cutting edge of the drill

gun nose drill

gun nose drill

Drill bit fixedly clamped in the prism.
the Mounting of the prism to fix the hole .
Rack mounting the prism set according to a scale position.

Using flow prism and the pitch of the engine supplied drill bit to the grinding circle and podnachivaet a jumper wire between the transverse cutting edges of the drill. Remember the feed value of the prism and attach the drill bit ago (about 3 turns). The flow of engine not touch.
Turn the prism for 180° and repeat all for the other side of the drill.

Additionally posted a video on sharpening drill bits on the machine.

The types and characteristics of reamers for metal

a Reamer is a cutting tool used for reaming of holes with high precision. Accuracy class scan is much higher than that of conventional drill bits for metal, so she adjusted the hole after drilling, if you need higher precision.

a drill with a diameter of 9 mm, and the real get the holes equal to 9.4 mm, so use a reamer to get a perfect hole with a diameter of 10 mm.

View scan

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