Re: Forstner bits
- From: John Martin <jmartin957@xxxxxxx>
- Date: Fri, 27 Jun 2008 07:52:48 -0700 (PDT)
On Jun 26, 7:08 am, "Swingman" <k...@xxxxxxxxxx> wrote:
"John Martin" wrote
So.. my answer is "No, they ain't ment to be used in a drill."
(For reference, I was using a Rockler steel - not carbon - forstner bit.)
Jason BucklerThey're not meant to be used in a hand-held drill only because there
is no central point to locate the bit. If you don't hold them
perfectly straight - and sometimes even if you do - they can skate all
over the workpiece.
Then your not talking about a "Forstner" bit ... proper Forstner bits indeed
have a point, which is called the "gimlet point", as named by the man who
invented the bit.
Last update: 5/14/08
KarlC@ (the obvious)
Oh, I most definitely am. The Forstners I use are almost all by
Connecticut Valley, BGI or PM - companies that have been making them
for well over 100 years. Machine shanks and bit brace shanks. Some
have small points that extend below the rim, some don't. On none of
them does the center point extend more than about 1/16" below the
rim. Of those that don't, some never did - it's not a re-sharpening
mistake. The Forstner bits are meant to be guided by their rims, not
their center points.
I even checked a couple of really big Forstners I have - 2-5/8" and
2-3/4", 3/4" shanks, about a foot long. Conn Valley, but they don't
show them in their product list anymore. Original factory grinds.
Each has a central point, but it's flat-topped and about 1/4" wide -
it's certainly not intended to guide the bit.
With the brace bits, one trick is to turn them backward at first to
get the rim to dig in slightly before you start to cut.
I've got no idea what was in Benjamin Forstner's original patents -
all I know is that the companies that have been making them from the
beginning have been making them without center points large enough to
significantly guide them. They do help in getting them on the center
mark, but that's about it. If you had a gimlet point, you wouldn't
get a flat-bottomed hole, would you?
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