What are the good methods for grinding milling cutters? Summary of over 20 years of experience as a machining teacher

How can I grind the milling cutter well?

Before grinding, it is necessary to inspect the grinding wheel. If any issues such as grinding wheel runout, irregular cylindrical surface, or excessive rounded corners are found, it is necessary to repair them. Generally, the cylindrical surface of the grinding wheel can be repaired using a grinding wheel corrector (such as a diamond corrector or a tooth blade corrector), or a waste grinding wheel with relatively high abrasive hardness can be used for repair. If the side plane of the grinding wheel is no longer flat, the grinding wheel can be replaced.

End face grinding technology of end mills

1. The Technology of Grinding the End Face of End Mills

Regardless of the number of blade end mills, the first step is to grind the end face of the blade perpendicular to the axis, which is the key to ensuring that the outstanding point of the blade can be in the same plane. There are the following methods for correcting the perpendicularity of the blade end face relative to the milling cutter axis.

① Visual inspection. You can use a flat plate to lower the edge of the end milling cutter facing down on the plate and observe the left and right tilt angles. Then rotate the milling cutter 180 ° and observe its left and right tilt angle. If the tilt angle observed twice in the same direction is different, it needs to be polished until the tilt angle observed twice in the same direction is the same. Afterwards, rotate the milling cutter by 90 ° and repeat the above action.

② Correct with a square ruler. On a flat plate, use a 90 ° square to calibrate. After leveling the milling cutter and square, observe whether there is a gap or even gap between the milling cutter and square. Then, determine the verticality of the milling cutter based on the gap and grind the milling cutter.

③ Self correction. Clamp the end milling cutter onto the chuck of the drilling or milling machine, place a waste grinding wheel underneath, select an appropriate rotational speed to start the machine, and then move the milling cutter down to grind on the grinding wheel, and perform grinding according to the end face grinding situation.

2. The Technology of Opening Cross Chip Removal Slot with End Milling Cutter

If there is no circular groove on the front end face of a four blade end milling cutter, it is necessary to use the rounded corner of the grinding wheel along the milling cutter

Reopen the cross groove in the direction of the spiral groove, with a depth of about 1-2mm (too deep is easy to crack, and too shallow is not easy to grind out the secondary rear corner). When slotting, be careful not to touch the side of the grinding wheel with another blade below (note: this cross groove has a chip removal function. If it is not slotted, the inclination angle of the blade that is recessed towards the middle should be increased).

3. Grinding Technology for End Face Cutting Edge of End Mills

① When grinding each edge separately, use the tip of each edge as the benchmark, and keep the tip as the principle. Grind the front angle (without chipping), back angle, secondary back angle (if a large cutting amount requires good strength, it is recommended to add a large blade wedge angle in front of the grinding tool), and the edge inclination angle.

② The selection of angles is for a rear angle of 6 ° to 8 °, and for a secondary rear angle of 30 ° to 45 °, the blade inclination angle is 1 ° to 3 °. The selection of the back angle depends on the hardness of the workpiece, and if the material hardness is high, the angle will be smaller; The principle for selecting the angle of blade inclination is that all four blades must be concave in the middle, and the flatter the angle, the better the roughness accuracy. At this point, the deeper the machining depth (such as greater than 2mm but within the allowable range), the better the roughness accuracy will be, because the entire cutting edge is involved in the cutting result.

③ After the blade grinding is completed, the milling cutter is erected on a platform. If the axis is vertical, all the blade tips can be leveled, and the deviation angle of the blade can be evenly aligned, which can meet the requirements.

At this point, it is also possible to use a 90 ° right angle ruler on a flat plate for calibration. After leveling, observe whether there is a gap or whether the gap is even between the milling cutter and the right angle ruler. Generally, observe the two relatively high feet first (the two feet that touch the bottom first). 

If they are not perpendicular, polish the higher feet until the two opposite feet are the same height (i.e. vertical). At this point, there is a height difference between these two feet and the other two opposite feet, and the milling cutter will swing. At this point, lower both higher feet simultaneously. Similarly, rotate the milling cutter 90 ° again to observe the verticality of the other two opposite feet, ※ until all four feet touch the bottom at the same time and make the milling cutter perpendicular. The milling cutter after grinding.

In manual sharpening, the height and angles of the blade are not easy to grasp. During training, it should vary from person to person, as long as you pay attention to grinding a little back corner. If the top edge is uneven, it is only necessary to make the blade tip outstanding. In addition, if it is not for the case of cleaning the inner cavity, a chamfer greater than 0.2mm can be ground at the blade tip to increase the strength of the blade tip.

4. Grinding Technology for the Main Edge (i.e. Side Edge) of End Milling Cutter

If the main edge of the end milling cutter is worn, it is necessary to grind it along the spiral line on the grinding wheel (smaller diameter is better) (which is difficult for beginners to grind well). But after grinding, there is usually a taper, and the smaller the taper, the higher the level of operation.