Drill bits

[GrottoParticipant @grotto]

I recently bought a bunch of drill bits and when sorting through them found a few are left hand.

I'll be able to use them in my mill, but wondered why they are made. I guess there’s a good reason, just can’t think of it. Anyone know why?

[GrottoParticipant @grotto]

[Michael GilliganParticipant @michaelgilligan61133]

One good use is for drilling-out broken right hand threaded screws.

MichaelG.

[Simon Williams 3Participant @simonwilliams3]

Hoard them carefully, and wait for the day you need to drill out a broken off bolt in something completely irreplaceable. They are absolutely brilliant at catching the remnant bolt, at which point it unscrews itself out of the blind hole like magic. Better than an easi-out any day.

Don't use them in a keyless chuck – many such won't hold in reverse. A keyed chuck (generally) will.

Rgds Simon

Edit – MichaelG types faster than I.

Edited By Simon Williams 3 on 25/05/2019 10:08:40

[CirclipParticipant @circlip]

They may have come from a flat pack furniture manufacturer. On multi drilling heads, some of the drill "chucks" rotate in reverse due to the centre spacing.

Regards Ian.

[Mark P.Participant @markp]

Loads on ebay.

Mark P.

[Anonymous]

Some production lathes normally run in reverse, like my Britan, so left hand drills are standard.

Andrew

[roy entwistleParticipant @royentwistle24699]

Drilling left handed holes obviously

Roy

[JohnFParticipant @johnf59703]

Boley made a capstan lathe similar I guess to Andrews Britan, also ran in reverse with the toolbox/holder at the rear thus LH drills we needed

John

[larry phelan 1Participant @larryphelan1]

Never thought about drilling left hand holes !!!

True,you learn something new every day.

Keep them coming.

[V8EngParticipant @v8eng]

Don’t forget to use left hand threaded taps with them.

[duncan webster 1Participant @duncanwebster1]

Then you'll need a left handed spanner to wind the bolts in

[Jeff DaymanParticipant @jeffdayman43397]

As mentioned on an earlier thread, left handed drills are very handy for working on the port engines of twin screw ships, and also LHD cars as used in North America. By the way Duncan, most mechanics' toolboxes in the North America are fully stocked with left handed wrenches of various types, a few of which can be used on right handed fasteners also…..not sure about toolboxes in the UK……

[Simon Williams 3Participant @simonwilliams3]

If you want to drill two holes which are truly independent of each other, drill one left hand and the other right hand.

Because the left hand never knows what the right hand is doing

[roy entwistleParticipant @royentwistle24699]

Left handed spanners are easy to recognize, left handed screwdrivers are not as easy especially cross point ones

Roy

[Mike PooleParticipant @mikepoole82104]

Can you fill a hole with left handed drill? Could be useful for a hole drilled in the wrong place.

Mike

[roy entwistleParticipant @royentwistle24699]

Mike Now you're just being silly

Roy

[Jeff DaymanParticipant @jeffdayman43397]

Hold on Roy, Mike is on to something. I'm pretty sure if I put a 1/8" dia left hand drill in the electrode holder of my old Lincoln 225 arc welder I can fill a hole ….. as long as the ground lead and clamp are in place on the plate with the hole!

[roy entwistleParticipant @royentwistle24699]

Jeff OK I'll hold my hands up

Roy

[Mike PooleParticipant @mikepoole82104]

Posted by roy entwistle on 26/05/2019 14:16:32:

Mike Now you're just being silly

Roy

Guilty I’m afraid.

Mike

[HollowpointParticipant @hollowpoint]

Maybe they are Australian? To counter that they are upside down and spinning the wrong way? 😄

[mark costello 1Participant @markcostello1]

Don't forget the left hand cutting fluid. Wrong hand fluid leads to drills and taps binding. NOW You know.

[Neil WyattModerator @neilwyatt]

Posted by mark costello 1 on 28/05/2019 19:06:24:

Don't forget the left hand cutting fluid. Wrong hand fluid leads to drills and taps binding. NOW You know.

You can check which you have by using polarised light to check for laevorotation.

Neil

[Jeff DaymanParticipant @jeffdayman43397]

Neil – one concern re your note – Hard to check using polarised light when you aren't at either North or South pole, or in Poland.

However I think if you run the cutting oil through a funnel and watch which direction it spirals, you can tell if it's right hand or left hand type oil……

If it spirals left it may be NASCAR rated cutting oil……

[Bruce NewmanParticipant @brucenewman56212]

When I was an apprentice in the late 60's I spent a period of time in a large auto lathe shop with CAV automatic lathes which could only run fast in one direction and slow in the other.

Components with threads were made with all the tools, including the drills, with the lathe running fast backwards then the lathe was run slowly forwards when cutting threads and then fast backwards when backing out the thread cutting tools. this was done to get the shortest possible cycle time which when making thousands of components and saved a lot of time. A lot of left hand drills were used.

[Author]

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