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John John is offline
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Default Drill bit question

"Al A." wrote:

john wrote:


SteveB wrote:
I bought a bunch of drill bits at yard sales recently. Some only have
flutes about a third of the way up the shaft, then clear shaft.
They're as long as normal bits, so they haven't been resharpened until
becoming that short. Can someone explain these to me?

Steve

They could be spotting drills or just a special ordered drill. Spotting
drills are used to locate or spot a drilled hole. They are made with
short flutes so they will be still and not wander when they first touch
the metal.


John


I have seen something similar used in places that work primarily with
thin material and sheetmetal type stuff. The work piece is never very
thick so you don't need full length flutes, but still have enough length
on the bit to reach places that a stubby bit would not. I suppose it
makes them more rigid and perhaps less expensive. There is a generic
name for them that is escaping me right now.


Yup. Some of the short flute drills are used with sheetmetal work. I
used them for many years. The short flute on them was nice because when
you came to the end of the flute you kept going to clean the little bit
of metal left in an otherwise round hole. For riveting this was
essential to get the rivet to go into the hole. I used to buy them from
a guy that had a boothe in the Ft. lauderdale Thunderbird flea market
who sold tooling, drills and a bunch of other related stuff. The
spotting drills have a different angle than the other drills. the
spotting drills are usually 90 degrees.



John