The Magic of a Left-Hand Drill

The other day I managed to remove a broken screw from a very expensive casting. Specifically, the engine casing of a Ducati motorcycle. But the job turned out to be a breeze using a backwards drill bit!

Extractor Kit with Left-Hand Drill Bits

A previous “mechanic” had broken one of four of the M6x16 sump cover bolts. Instead of removing the remnants they had globbed it over with RTV silicone for the another poor schmuck to deal with at the next oil change. A few minutes after discovering this I could fully understand why. Being at the lowest point on the engine, it’s not an easy feat to find room for a drill… and then drill into the screw while upside down. But disregarding this hurdle, I resolved to remove the broken screw and repair it properly.

Once the bike was precariously elevated I got to work.

One of the handiest tools in my arsenal is a 10-piece extractor kit that has five “easy out” extractors and five left-hand twist drills. I center punched the broken screw and selected the drill recommended for an M6 bolt. As I slowly drilled shavings rolled down the drill into the drip tray below. After a couple of minutes the drill jerked a little and seemed to dig in deeper. I stopped for a moment– then noticed a tiny shard of threaded steel protruding from the hole. Could it be?!? I eased on the drill again and the broken screw slowly turned down out of the hole. I hadn’t even used the extractor!

Yuck! No threads are visible in the hole in the lower left because it was filled with RTV.

I confess, the left-hand drills in this set seemed silly at first. Does it matter which direction the drill turns? Would it really transmit that much torque? I’m a firm believer now.

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