Left handed drills?

I recently came across a youtube vid showing removal of a broken bolt with a left handed drill bit.

Other than the removal of stubborn bolts and studs  why do they make left handed drill bits?

Both my rather old mains drills and the pillar drill all turn clockwise for right handed drill bits. Only the cordless drill has a reverse function.

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iceng3 years ago

Neat thread,

What would you do with a broken drill bit in soft aluminum ?? :-)

rickharris (author)  iceng3 years ago

Assuming you are unable to drill in from the back and punch out the drill bit then I would try



It works best warm.

Excellent answer !

You get a patch !!

The people who worked for Bill Lear used an acid which did not bother Al and eventually saved the piece

rickharris (author)  iceng3 years ago

:-) I still want to know why they manufacture LH drill bits.

The best reason I know was way before electronics and NIB magnets, when multy-head revolver screw machines were programmed by cams and gears and for simplicity alternate heads turned in opposite directions, because it saved a reverse rotation gear.

The complicated working bits were all clockwise so it was easiest to make

the pre-hole drills, LH for the CCW rotating heads.

rickharris (author)  Nicholas Lee1 year ago


Thanks for re-affirming my comment on this thread over a year ago...

iceng iceng1 year ago

BTW, years ago when I worked for Chicago Skill saw we made AC reversing drills which required a special through shaft screw so that the chuck would not unscrew itself when turning CCW...

Reversing AC hand drills have to use neutrally wound armatures to provide equal rotation speed both ways...


I was there when we had to diffuse our own SCRs (thyristors) because the available units readily failed in a power tool.

mrandle3 years ago

I think you hit the nail on the head and that they are only used for removing stubborn bolts. I can imagine you could use them like a regular drill bit so maybe it would be worth only having left handed bits? Even then i've always drilled bolts with a regular drill bit and screwed in a left handed screw extractor.

mh76dk mrandle3 years ago

I had to look up what a "left handed screw extractor" is and came across http://en.wikipedia.org/wiki/Screw_extractor which mentions these left-handed bits and calls them "Spiral fluted extractor".

rickharris (author)  mh76dk3 years ago

commercially called "Easy outs." (actually in practice not always all that easy)

If you know what they are why did you ask?


rickharris (author)  Josehf Murchison3 years ago

An easy out isn't the same as a left handed twist bit.

The Easy out has a conical coarse left handed thread.

A LH Twist drill bit looks just like a normal one but twisted the other way.

As in picture below.

Although I know about using a LH Drill bit to remove a broken bolt - I find it hard to beleive they make them just for this purpose.

easy out.jpg

I don't see any use for them.

Left handed drill bits are for drilling out screws or bolts that have snapped off in a hole that goes all the way through something, rather than a "blind" hole. Imagine a motor or some other machine that had sensitive internal workings. If you drilled the snapped off screw with a right hand drill it could screw all the way in through the hole and fall into the motor which would then have to be removed, dismantled etc. Quite often a snapped screw or bolt that no longer has any tension on it will easily be turned by the action of the drill.

And the question was what other reason do they have to exist?

I wasn't answering the question I was just joining the discussion (just like you), and replying to your comment "I don't see any use for them". I thought I might have made things a bit clearer for others who may be reading this. Shall I delete my comment for you?

No don't delete we are still looking for some other use for them. I did say in an earlier comment if the bit catches while drilling the hole for the easy out.

Maybe I should have added and pushed in the broken stud.

Yes, I see. My apologies.

rickharris (author)  Josehf Murchison3 years ago

+1 but you can buy them.

They would be a special order here in Canada most likely a throw back tool.

See my comment to Josehf.

rickharris (author)  mh76dk3 years ago

See my post below.

Burf3 years ago

My old man was left handed and he had
dozen or so left hand twist drill bits he he in his hand cranked, egg
beater drill. He could use his strong hand to crank the drill without
cranking, what to him was backwards.

I've also heard they are
used in some manufacturing processes where they drill two holes
simultaneously with a single power gear driving both drill chucks.

rickharris (author)  Burf3 years ago

Interesting idea, BUT surly all he had to do was turn the drill backwards

Burf rickharris3 years ago

Nope. Take a look at the way an egg beater drill works. Using a right hand twist bit, cranking the
drill right handed pushes the handle toward the workpiece while cranking the
drill with your left hand tends to pull it away from the workpiece. A left hand twist bit reverses that issue.

mrandle Burf3 years ago

Wow that makes alot of sense. Very specific scenario bu hey it works!

There is more than one reason for left hand thread and other tools.

Left had tools are safer for left handed people.

The best example is chain saws all of them are made right handed and 80% of the accidents with chain saws are by left handed people.

Scissors made right handed won't cut if you use them left handed.

And then there is torque spinning clock wise a clock wise thread tightens in a sudden stop, spinning counter clockwise a clockwise thread loosens in a sudden stop.

Then there are threaded tightener's you have a right hand thread on one side and a left hand thread on the other. Turn the nut one way and the tightener is shorter, turn the nut the other way and it expands.

As for a left handed drill bit they are not necessary other than if the bit catches while drilling the hole for the easy out tool.

So my question is was it a drill bit or an easy out tool?


Exactly I can't see much point in this unless its a special bit that had some kind of grip part way up the bit( if this doesn't exist it's a genius invention ;). I can't imagine a spinning drill is going to have any more torque than a wrench. Maybe the vibration would loosen it but no different than the regular bit and using a fluted extractor.

I have a number of easy outs and personally the best method to remove broken studs I found is to throw the easy out in the trash and use a blowtorch, vice grips, and cold water.

Most of the studs and bolts that break off on me are rusted in place; the worst ones for this are exhaust manifolds and the breaks on cars. They never break off flush so there is a little of the stud sticking out, you heat the stud until it is red hot, and then cool it with the water, then wiggle with the vice grips, and repeat until the stud comes out.

This method works so well I consider easy outs a waste of money.


Thats if they break off with enough to grab. I had to use them in the exact situation you described only it was the intake\exhaut on my 65 mustang. You can't always use a torch either if there are flammible things near by. I wouldn't go as far to say they are a waste as there are certain situations where they are neccesary.

It works with almost nothing and when it is below the surface use a center punch to get it moving.

They are made to remove screws and bolts with stripped heads and nothing more.

rickharris (author)  mpilchfamily3 years ago

This is what I thought

rickharris (author)  rickharris3 years ago

But I find it hard to believe they make them just for this reason.

Its a novelty item like left handed pencils, left handed coffee mugs, left handed blue jeans. :-)

rickharris (author)  thematthatter3 years ago

Too costly to manufacture for novelity :-)

mh76dk3 years ago

Since all the good answers are already taken; Perhaps it is an australian thing?

Ha, Ha, Ha, I like that but you forgot South America and South Africa the toilet swirls the other way there also.