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It is shown that the exact angle at the top of 120º does not practically affect the operation of the drill.
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There is a lot of information on the Internet about sharpening drills. The essence of all methods is to accurately maintain the value of the angle at the top - 120º.
For this, hex nuts are used, from which fixtures are made. When sharpening the drill with the help of these devices, an angle of 120º is maintained with copying this angle along the faces of the nuts.
This video shows with examples that keeping the exact angle at the top of 120º is not necessary at all.
I took three new identical drills with an angle at the top of 118º.
Two of them sharpened and measured the angles. One had a vertex angle of 100º, and the other had 147º.
Shown how these drills drill. Drill power 420 W, 600 rpm.
I took a steel corner with a shelf thickness of 4 mm and drilled it in turn with all three drills: a drill with factory sharpening - 118º, a drill with an angle of 147º, a drill with an angle of 100º.
In all cases, I set the maximum speed and tried to create the same feed force for the drill.
It was seen that all three drills - with different angles at the top - drill equally well. And the drilling time is about the same.
Point angle recommendations are available for drilling various materials. Basically, the angle is in the range (90…140)º.
These recommendations refer to the optimal cutting conditions when it is necessary to make large batches of parts and ensure high labor productivity. But this does not mean that drills with other angles will not drill these materials.
I drilled steel with 100º, 118º, 147º point drills. And they recommend (116 ... 118)º.
Also shown is the drilling of aluminum (duralumin) with a drill with an angle of 100º. And they recommend 140º. The drill drills well.
Drilling wood with a 100º drill is also shown. And they recommend 140º. It also drills well.
Amateurs have a one-time job, and one drill is used to drill various materials. And therefore, the angle at the top can be made any within reasonable limits, in the region of 120º.
As I have shown, the work of the drill does not depend on the angle at the top. The shavings work just as well.
The greatest influence on the operation of the drill is the size of the back angle. That is, it is very important to properly sharpen the back surface of the drill.
I hope this video will make it easier for you to sharpen your drills.
It doesn't take much time or effort to ensure that the vertex angle is exactly 120º, as some recommend in their videos.
This angle can be maintained when sharpening by eye, approximately.
And you don’t need to control this angle with goniometers and templates.