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Cutting Holes

by HarryColemanHarryColeman 02 Sep 2018 08:12

My name is Harry Coleman. I am an automotive technician.
Since I was born, I just broke toys, picture frames, etc, all accidentally, of course. With the time I started to take them apart purposefully. As I grew older I realized I should probably put some things back together. I still haven’t gotten that clock to work.

In my blog I'll share my experience and ideas with brothers-technicians. And feel free to comment my posts and share your thoughts too.


When drilling holes in steel sheets, there are two main problems.
1. Complexity of alignment, at the beginning of the rotation, the cutting edges are shifted.
2. The shape of the hole is not round, but triangular, bending of the surface (often with it the detachment of the paint), need for subsequent revision of the round file. In addition, during the drilling, at the moment of biting the edges of the material, a sharp jerk takes place, which either turns out the hands or deforms the workpiece.

Advantages of the best spade bits.

- One tool for different diameters. For example, the Yato YT-44740 can replace 12 sizes in the range of 6 to 38 mm and fix the defective hole after the spiral.
- Special sharpening of the cutting edges of the first stage. Allows you to self-center without moving away.
- The massive base does not allow to bend under critical overloads.
- When passing the next step, the next, removes the bevel by removing the burrs.
- Production of holes up to 38 mm in diameter with the possibility of clamping the shank into the holder of an electric drill or a drilling machine calculated up to 10 or 13 mm.
- Fast visual identification. Inside the groove, opposite to each step of the drill, carrots are dimensioned, which allows them to orientate themselves in them without a caliper.
- Possibility of repeated re-sharpening with weakening cutting ability.
Are there any shortcomings in this tooling?

- If you often have to work with small diameters, then when they become blunt, work on steel becomes big.
- Drilling sizes of more than 20 mm requires a drive more powerful than 800 watts.
- During the passage of the last maximum step and the failure of the tool through the steel sheet, difficulties arise with its removal. To facilitate pulling out, some manufacturers from the end of the wide part perform a chamfer.
- On some models of inexpensive Chinese step drills, the diameters of the steps may be several tenths of a millimeter, usually in the minus, different from the exact size.
- When you are in one drawer or bag with another tool, in contact with it, the first cutting step, due to the high hardness, can break off, and if you fall on a hard surface, the drill itself may also burst.

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