Do you want to center hole? How deep is fit? Or do not hit it directly? My drill bit and the center hole contact point are easy to collapse
A very shallow point can be;Because once too deep, and the center hole of the aperture is less than the drill bit to drill aperture, so is not in contact with the workpiece, but the main cutting edge part in contact with the workpiece, so cause drill can not correctly centering, so easy to collapse;In the deep hole processing, it is necessary to use pre hole; the general pre hole is the drill bit, the hole size is the same, and the depth is usually about 3 times;I hope I can help you
Normally, carbide drills are used without the central hole;Center hole as you said the drill is easy to collapse; (the center hole you were a little deep);Even if you hit a center hole, the effect is the location of the mark hole; so don't go too far.
Detailed analysis of the specific circumstances, the general drilling site is very smooth, you do not need to hit the center hole. If the borehole is uneven or drilled on the slope, a center hole is required. If the drill hole is first deflected and re corrected, a center hole is also required.
