On 2016-12-08, Cydrome Leader wrote:
DoN. Nichols wrote:
On 2016-12-06, Christopher Tidy wrote:
Hi folks,

I need an example for an article. Can anyone think of a modern product
which uses plain bearings in a demanding application? I'm not talking

[ ... ]

Well ... how old do you accept as "modern"?

I've got a nice Cameron Precision sensitive drill press, which I
got new sometime in the 1970s which has plain bearings on the spindle.
It goes up to pretty high RPMs. The spindle ends in a JT-0 and mine
came with a 1/8" Albrecht chuck on it. to give an idea of size.)

Got one of those too. They just discontinued the classic looking model for
a newer design. My guess is they ran out of castings or motor parts from
decades ago. While way newer than yours, it has plain bearings as well.
With a little practice I was able to drill through the widest part of a
brass key for about a 30x width hole with good straightness. There's no
play that I can measure, and they claim speeds up to 30,000 RPM are OK.
Small bearings can run fast, so there probably isn't any real sorcery
behind their bearings other than there's some hand fitting going on at the
factory where they take out all the play. The original motors are real
screwy, so there's no loss if they ditched those for something better,
even if it doesn't match the look of the original.

Yes -- universal motors with a three-position switch, off, low,
and high speeds (infinite series resistance, fixed series resistance, or
zero series resistance -- for approximate values of infinite and zero. :-)

I have mine plugged into a speed controller for older (fixed
speed) Dremels, and keep the motor switch set for "high". I had to
replace the original switch on one at work when it started arcing when
switched to "stop" once. :-) Mine survived nicely, so far. :-)

I've even used it, with one of the solid carbide bits made for
printed circuit boards to drill out the center of a broken 6-32 tap.

Enjoy,
DoN.

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