What happens if I use the counterclockwise setting on my power drill to drill a hole?

Question

I've learned that, "Almost all drilling bits have to be rotated clockwise to achieve drilling." - Source

What is wrong, exactly, with using the "L" setting (counterclockwise setting) on my cordless power drill to drill a hole (using a standard drill bit)?

Won't the hole still be created at the end of the day, regardless of the direction? I don't understand the "real-world" difference. Are you able to visually tell the difference between the two holes (the hole drilled on the clockwise setting vs. the hole drilled on the counterclockwise setting)?

Answer 1

Conventional drill bits are designed to cut in only one direction, unless otherwise noted. I think one has to make special effort to find a left-cutting bit, although some screw extractors with an integrated cutter will be left-cutting.

Because a drill bit cuts, one wants the cutting edge to engage the work as it rotates. If used in the reverse direction, the cutting edge will drag and become dull in short order.

Along with the dulling, great heat will be generated from the friction. I have read on this forum of people who have used reverse direction on a conventional drill bit to effectively melt through plastic. Drilling plastic requires special bits or special technique to prevent cracking the plastic.

Answer 2

Drilling counterclockwise is like razoring holding the razor upside down; the blade touches the thing to be cut, but it has no effect as it slides over it.

Your best bet is that if you cut wood this way, you (1) run out of battery soon and (2) burn the wood as the friction can be very large.

Answer 3

Running twist bits in reverse drags the cutting edges over the surface rather than shaving off material. In soft materials like wood you may scrape your way through regardless, in steel you'd make considerably less progress.

A more sinister issue is that the point of the bit being deprived of any bite will want to wander when starting the hole. Softwoods mask the problem to a certain degree because you can create a large starting divot by arm strength alone. On metals and engineered lumber the effect is more pronounced.

Worst of all, running a twist bit backwards greatly retards the travel of cuttings up the flutes. Rather than removing material the drill abrades it against the bottom of the hole until it piles up high enough to spill out. In deep holes this will either lead to the bit getting stuck by the cuttings forcing their way up the perimeter of the hole or cutting a hole that's out of round.

Answer 4

I have used this technique when working with Plexiglas and fine metals and wood. First you are not drilling through the entire surface backwards, you are drilling through about 90% to 95% of the material and change the direction to pierce the last bit. This technique prevents Cracking in Plexiglas, damaging the wood when the drill bit comes through and with metal especially the last part the drill usually catches before exiting the material, by reversing the bit it prevents the metal from grabbing the bit and bending.