09-27-2012, 07:51 PM
Wondering how many of you have a set of left hand drills, and what have you used them for.
sasquatch, proud to be a member of MetalworkingFun since Jul 2012.
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Wondering?
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09-27-2012, 08:10 PM
Don't have a set. They're supposed to be for removing broken bolts I think, the idea being if they grab it will back the bolt out. Can't imagine them functioning very often, if the bolt broke its usually rusted in or over torqued, in either case it takes a fair bit of torque to remove the bolt, more than I can see the drilling action giving.
Free advice is worth exactly what you payed for it.
Greg
09-27-2012, 08:20 PM
From what i have read, they are best used for drilling out a broken bolt as you say,, but the advantage if drilling out a threaded hole is the left hand drill will not grab into the right hand threaded hole.
I,m wondering IF there are other practical uses for a set?
sasquatch, proud to be a member of MetalworkingFun since Jul 2012.
09-27-2012, 10:25 PM
From Wiki:
Left-hand bits are almost always twist bits and are predominantly used in the repetition engineering industry on screw machines or drilling heads. Left-handed drill bits allow a machining operation to continue where either the spindle cannot be reversed or the design of the machine makes it more efficient to run left-handed. With the increased use of the more versatile CNC machines, their use is less common than when specialized machines were required for machining tasks. Screw extractors are essentially left-hand bits of specialized shape, used to remove common right-hand screws whose heads are broken or too damaged to allow a screwdriver tip to engage, making use of a screwdriver impossible. The drill bit is pressed against the damaged head and rotated counter-clockwise and will tend to jam in the damaged head and then turn the screw counter-clockwise, unscrewing it. 
I have a couple of small sets. It's true that if the bolt or screw is heavily rusted or corroded in place, they aren't much help other than drilling a hole. But every now and then you run across a bolt or screw that snapped in tension and the top portion loosens up and falls out, leaving you with a stud half way down in the threaded hole.
Combine that with a transverse engine that sits 4 inches away from a uni-body sub-frame, and a left hand bit in a 90° angle drill can be your best friend sometimes. Especially if it keeps you from having to remove the engine to access the broken bolt location with a straight drill.  No chance at all with a RH twist drill though. 
Willie
09-28-2012, 06:25 PM
Thanks for the replies,, looking through the catalog, i'm thinking i will buy a few in "Stub Drill" lengths, mostly between 1/8th and just up to 1/2 inch.
I don't see that i will need a whole set, but a few sizes i could probably use at times.
sasquatch, proud to be a member of MetalworkingFun since Jul 2012.
09-28-2012, 06:31 PM
(09-28-2012, 06:25 PM)sasquatch Wrote: Thanks for the replies,, looking through the catalog, i'm thinking i will buy a few in "Stub Drill" lengths, mostly between 1/8th and just up to 1/2 inch. Don't bother with the ones from Harbor Freight. They aren't much good for anything harder than aluminum Randy
randyjaco, proud to be a member of MetalworkingFun since Jul 2012.
09-28-2012, 08:03 PM
Nope, not from HF randy,, i buy most of my stuff from KBC here in Canada.
sasquatch, proud to be a member of MetalworkingFun since Jul 2012.
09-29-2012, 08:36 PM
Hi,
I keep a few lefties, (besides myself  ), around for just such moments like Highpower mentioned. Sometimes they are the bacon savers to have. Just a couple of weeks ago I used a 1/16" left hand drill to pretty easily remove 4 broken #5 screws that were a good 3/32" below the surface of 3 face mills. 20 minutes and a nice chunk of change for my pocket. dalee
dalee, proud to be a member of MetalworkingFun since Aug 2012.
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