PDA

View Full Version : Left handed twist drills



old mart
02-23-2016, 04:20 PM
I've just seen a job lot of left hand twist drills on Ebay. Why are they made, what job would require them rather than an ordinary drill?:confused:

brian Rupnow
02-23-2016, 04:24 PM
Best thing ever for drilling out a broken stud. The fact that they are turning counterclockwise helps to break the stud loose, rather than tightening it.----brian

H380
02-23-2016, 04:24 PM
They work great to drill out broken bolts.

Willy
02-23-2016, 04:28 PM
The main reason I use them is to drill out broken bolts/studs that have right hand threads.
As often as not the drilling process combined with the torque transmitted thru to the stud one is drilling out is enough to remove said stud without resorting to other means.
If one has to drill out a broken bolt anyway he may as well be applying torque in the right direction.

Right hand twist drills essentially work the same on broken left hand threaded fasteners.

Frank Ford
02-23-2016, 04:32 PM
I believe lots of multiple spindle drilling machines have adjacent chucks rotating in opposite directions.

boslab
02-23-2016, 04:38 PM
I believe lots of multiple spindle drilling machines have adjacent chucks rotating in opposite directions.
That makes a lot of sense
Mark

Doozer
02-23-2016, 04:53 PM
They are sold for use in the southern hemisphere.

-Doozer

boslab
02-23-2016, 04:58 PM
Are all the threads left hand down the bottom end, suspicious I'm thinking
Mark

Rustybolt
02-23-2016, 05:13 PM
They were invented for screw machine work.
Many times the spindle was run in revese so forming could be done on the back slide and cutting off could be done on the front slide. It was important to have as many tools in the work as possible so drilling would start with the forming cycle. Also if the job reqired a left hand tapped hole.

Richard P Wilson
02-23-2016, 05:29 PM
Possibly all the above suggestions, though I was once told that using left handed drills meant that the workforce was less prone to pocketing them to take home!

geeb
02-23-2016, 05:55 PM
No Doozer, the ones in Aus are upside down (darn hard to drill a hole with them)

smithdoor
02-23-2016, 06:20 PM
They use on BS screw machinist
They only had two clucks they the high speed run rev then tap in low FW
Today use for removing broken screws

Dave



I've just seen a job lot of left hand twist drills on Ebay. Why are they made, what job would require them rather than an ordinary drill?:confused:

boslab
02-23-2016, 07:31 PM
What's a BS screw machinist?,
Mark

MyrtleLake
02-23-2016, 07:48 PM
Brown & Sharpe ... as in B&S automatics (or "screw machines (https://en.m.wikipedia.org/wiki/Automatic_lathe#Screw_machine)").

wierdscience
02-23-2016, 08:05 PM
I had to have 8 right hand and 7 left hand for this multi-spindle I built for a friend-

http://img.photobucket.com/albums/0903/wierdscience/MULTI.jpg (http://smg.photobucket.com/user/wierdscience/media/MULTI.jpg.html)

becksmachine
02-23-2016, 09:39 PM
I had to have 8 right hand and 7 left hand for this multi-spindle I built for a friend-

http://img.photobucket.com/albums/0903/wierdscience/MULTI.jpg (http://smg.photobucket.com/user/wierdscience/media/MULTI.jpg.html)

So what's the secret drive mechanism? I would guess gears?

Dave

J Tiers
02-23-2016, 10:51 PM
So what's the secret drive mechanism? I would guess gears?

Dave

Every other drill is reversed rotation from the ones on either side..... It would take more gears and more space to have them all alike.

The Artful Bodger
02-23-2016, 11:52 PM
They are sold for use in the southern hemisphere.

-Doozer

That is absolute nonsense! In the Southern Hemisphere the drills are the same but are sharpened from the other end.

flylo
02-23-2016, 11:56 PM
If you put the pointy end in the chuck it stays sharper much longer.

wierdscience
02-24-2016, 12:17 AM
So what's the secret drive mechanism? I would guess gears?

Dave

Yes,gears,some 20 pitch 20* pinon stock provided that to yield the 1" center distance.

boslab
02-24-2016, 12:22 AM
Brown & Sharpe ... as in B&S automatics (or "screw machines (https://en.m.wikipedia.org/wiki/Automatic_lathe#Screw_machine)").

Ooh
Thank you
Mark

Paul Alciatore
02-24-2016, 01:47 AM
Yup. I keep a small assortment of them for just that reason. They work like a charm and were successful almost every time I have used them for broken screw removal. I can't say that about any other method I have tried.




Best thing ever for drilling out a broken stud. The fact that they are turning counterclockwise helps to break the stud loose, rather than tightening it.----brian

darryl
02-24-2016, 02:06 AM
I had a right hand drill bit that I turned into a left hand in about 3 seconds- softest 'steel' I've ever seen. Dollar store crap-

Euph0ny
02-24-2016, 02:22 AM
I had a right hand drill bit that I turned into a left hand in about 3 seconds- softest 'steel' I've ever seen. Dollar store crap-

It does help if you buy decent-quality ones!

These German-made DIN-338 HSS-G ProJahn left-hand drills are what I use for getting out stuck screws in guns. Not really cheap, but when you need a left-hand drill, nothing else will do. Unfortunately, they don't come in cobalt-HSS, which would be even nicer:

https://www.nineka.de/Spiralbohrer-25-kurze-HSS-G-Bohrer-linksschneidend-1-13mm

https://www.nineka.de/Spiralbohrer-19-kurze-HSS-G-Bohrer-linksschneidend-1-10mm

MichaelP
02-24-2016, 02:23 AM
I've just seen a job lot of left hand twist drills on Ebay. Why are they made, what job would require them rather than an ordinary drill?:confused:
Same reason lathes and milling machines have a REVERSE. How else left-handed machinists would drill, turn and mill?

Besides, if a person is going to use a left-hand tap, he has to drill the hole with a left-hand drill.

Seastar
02-24-2016, 09:07 AM
I'm not going to comment.
This thread has already accumulated more than a normal share of wise a$$ remarks!
He He!
Bill

davidh
02-24-2016, 09:36 AM
i haver left hand cobalt M42 drills available, in in thru 29 pc. sets.

Euph0ny
02-24-2016, 10:44 AM
i haver left hand cobalt M42 drills available, in in thru 29 pc. sets.

Obviously you are not trying to sell anything on this forum, but if you were, what would those cost, and do they come in metric sizes?

lakeside53
02-24-2016, 12:24 PM
Yup. I keep a small assortment of them for just that reason. They work like a charm and were successful almost every time I have used them for broken screw removal. I can't say that about any other method I have tried.

I do too.. but every know and they the little &^%$#%'s find their way into the right hand drill cabinets where they hide; Thye are never to be found until you "use them" in a RH chuck.

old mart
02-25-2016, 01:31 PM
Thanks, some of the reasons even make sense, just don't use one in a keyless chuck.