Drill bits

This topic has 24 replies, 17 voices, and was last updated 28 May 2019 at 20:38 by Bruce Newman.

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25 May 2019 at 10:02 #410865
Grotto
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@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?
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25 May 2019 at 10:02 #9679
Grotto
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@grotto
25 May 2019 at 10:05 #410866
Michael Gilligan
Participant
@michaelgilligan61133
One good use is for drilling-out broken right hand threaded screws.

MichaelG.
25 May 2019 at 10:07 #410868
Simon Williams 3
Participant
@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
25 May 2019 at 10:30 #410871
Circlip
Participant
@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.
25 May 2019 at 10:32 #410872
Mark P.
Participant
@markp
Loads on ebay.

Mark P.
25 May 2019 at 11:03 #410877
Anonymous
Some production lathes normally run in reverse, like my Britan, so left hand drills are standard.

Andrew
25 May 2019 at 11:11 #410878
roy entwistle
Participant
@royentwistle24699
Drilling left handed holes obviously

Roy
25 May 2019 at 11:48 #410885
JohnF
Participant
@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
25 May 2019 at 17:36 #410933
larry phelan 1
Participant
@larryphelan1
Never thought about drilling left hand holes !!!

True,you learn something new every day.

Keep them coming.
25 May 2019 at 17:44 #410935
V8Eng
Participant
@v8eng
Don’t forget to use left hand threaded taps with them.
25 May 2019 at 23:57 #410967
duncan webster 1
Participant
@duncanwebster1
Then you'll need a left handed spanner to wind the bolts in
26 May 2019 at 00:49 #410969
Jeff Dayman
Participant
@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……
26 May 2019 at 07:35 #410975
Simon Williams 3
Participant
@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
26 May 2019 at 09:24 #410980
roy entwistle
Participant
@royentwistle24699
Left handed spanners are easy to recognize, left handed screwdrivers are not as easy especially cross point ones

Roy
26 May 2019 at 10:31 #410987
Mike Poole
Participant
@mikepoole82104
Can you fill a hole with left handed drill? Could be useful for a hole drilled in the wrong place.

Mike
26 May 2019 at 14:16 #411025
roy entwistle
Participant
@royentwistle24699
Mike Now you're just being silly

Roy
28 May 2019 at 00:59 #411274
Jeff Dayman
Participant
@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!
28 May 2019 at 09:22 #411302
roy entwistle
Participant
@royentwistle24699
Jeff OK I'll hold my hands up

Roy
28 May 2019 at 09:33 #411307
Mike Poole
Participant
@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
28 May 2019 at 09:48 #411309
Hollowpoint
Participant
@hollowpoint
Maybe they are Australian? To counter that they are upside down and spinning the wrong way? 😄
28 May 2019 at 19:06 #411382
mark costello 1
Participant
@markcostello1
Don't forget the left hand cutting fluid. Wrong hand fluid leads to drills and taps binding. NOW You know.
28 May 2019 at 19:37 #411390
Neil Wyatt
Moderator
@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
28 May 2019 at 19:54 #411394
Jeff Dayman
Participant
@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……
28 May 2019 at 20:38 #411401
Bruce Newman
Participant
@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.
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