Reverse Twist Drill Bits

Q

Qmavam

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Hi all,
Somewhere along the way, I ended up with some #28 drill bits that have a reverse twist on them.
Meaning they cut fine in reverse. (dzmn, e$#@, that bit sure is dull, Ohhhh!)
The only info I find is they are made for removing broken screws.
"When a reverse bit is inserted into a chuck and the drill is run counter-clockwise, this means that the bit performs the same sort of cutting action that a standard drill bit does when moving clockwise. This can be extremely useful as a method of screw extraction when the slots on a screw head have been worn away."
I don't see the advantage of reverse over forward drilling when "the slots on a screw head have been worn away."
The advantage I do see is you are not further tightening the screw by the drilling action, seems minor, but maybe helpful.
What is the purpose of a reverse twist drill bit?
Mikek
 
I have a set of left-hand drill bits that I use for smaller screw extraction.
Not always but fairly often the broken screw will begin to back out enough that I can remove it without needing to use an extractor.
I'm not aware of any other benefits to using them, but there may be other applications as well.
 
I also keep some left hand bits on hand for removing broken screws or bolts. They will often back the broken bolt out. Use an end mill first to make a flat spot.
 
The idea isn't that it prevents further tightening the screw, it's that if the screw suddenly loosens (because of heat, pressure, vibration, etc) the bit will grab it and back it out. Either partially and then you can grab it with something and finish removing it, or it will screw it out completely.

Doesn't always work out that way, but when it does I usually finish the job with a "happy dance"......;)
 
Hey! If you have them, use them. What would be wrong with out side the box drilling anyway? I'm a left
handed Norwegian so can't see much difference in the direction it turns unless one is trying to get lucky
removing a screw...
 
I have two sets of SnapOn extractor sets. They came with L/H drills and I used them for 40-50 years for all the reasons above. They are some awful expensive. About 3-4 times a decent brand of drill. The only question in my mind is the oddball size. The good spline extractor sets were 1/8.3/16.14. 5/16 and 3/8. If you got it, use it, it won't hurt and may help.
 
Use them every day for broken bolt removal . Sometimes they work and sometimes they don't . Depends on just how stuck the bolts are .
 
One thing about their use, make sure to drill the hole as close to the exact center of the fastener as possible so that if you do not succeed in removing the fastener, you can still drill it out and re-tap it without running off to one side and losing threads.
 
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