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Posted by Nigel Eaton on April 6, 2008, 4:04 pm
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>
>> Amongst my collection I have a 7/16th Left Hand Twist drill.
>> What would this have ever been used for. First that I have ever seen.
>
>The main use in ye olde times was for multiple spindle gear driven drilling
>heads where alternate heads run in opposite directions rather than employ
>two gears per drive to keep the rotation in the same direction at extra cost
>and complexity. There's no actual drilling benefit in the direction of
>rotation unless the machine itself requires it other than supposedly
>sometimes for drilling out broken studs where you want any forces acting to
>try and remove the stud not drive it further in. Personally I've never come
>across a stud so corroded into place that it needed drilling out that could
>have been affected in any way by the direction you then drilled into it.
>They generally won't even budge once you've drilled them and then screwed a
>stud extractor in.
I use them fairly frequently for getting knackered studs / sheared bolts
/ stuff out of Japanese motorcycles. They really do a nice job, in my
experience. I start off with a small size, then work up. Usually the bit
grabs the bolt / stud / whatever before I get anywhere near the threads
and spins the remnants out.
--
Nigel
When the only tools you have are a Bridgeport, a CNC Taig Mill, a Colchester
and assorted other stuff, every problem looks like a steam engine.
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> What would this have ever been used for. First that I have ever seen.
>
> --
>
> Richard
>
> Email address is valid but remove burrs before sending!