I've been using the ceramic guides for over a year, and find them a superior
way of controlling the blade when cutting wet wood. Bought the thrust
"bearings" a couple of months ago, and have been satisfied with them - until
today.

The directions say that "harmless" sparks may be produced, and so they
seemed until I saw smoke curling up from under the insert today. I had cut
some spalted beech earlier, without the vacuum attachment, and the sparks
ignited some of the punky dust which had collected in the little pocket
formed by the guide holders and thrust bearing. Don't know if the vacuum
would have prevented or exacerbated the problem, but I'm seriously
contemplating a return to the steel bearings, at least below, where dust
might create a tinder situation.

You're warned.

George wrote:

I've been using the ceramic guides for over a year, and find them a superior
way of controlling the blade when cutting wet wood. Bought the thrust
"bearings" a couple of months ago, and have been satisfied with them - until
today.

The directions say that "harmless" sparks may be produced, and so they
seemed until ...

What causes the sparks?

And I think sparks are never "harmless" in a wood shop...

"Duane Bozarth" wrote in message
...

What causes the sparks?

And I think sparks are never "harmless" in a wood shop...

The ceramic (flint) and the blade (steel).

I'm fussy about sawdust near the grinding wheel myself, and won't use my
belt/disk sander for sharpening because of possible dust, but I'm sure most
folks regard the sparks as events with so little fuel in the form of filing
that they can't ignite something else.

George wrote:

"Duane Bozarth" wrote in message
...

What causes the sparks?

And I think sparks are never "harmless" in a wood shop...

The ceramic (flint) and the blade (steel).

But if they're adjusted properly they shouldn't be against a tooth
edge???
That's where I'm confused about the manufacturer saying there're going
to be some...

I'm fussy about sawdust near the grinding wheel myself, and won't use my
belt/disk sander for sharpening because of possible dust, but I'm sure most
folks regard the sparks as events with so little fuel in the form of filing
that they can't ignite something else.

Most of the time that's true...it's the once that's a potential problem
if the chunk (of ceramic in this case) just happens to be large enough
to hold enough energy and the fuel is just close enough to the ignition
point...

"Duane Bozarth" wrote in message
...
George wrote:

"Duane Bozarth" wrote in message
...

What causes the sparks?

And I think sparks are never "harmless" in a wood shop...

The ceramic (flint) and the blade (steel).

But if they're adjusted properly they shouldn't be against a tooth
edge???
That's where I'm confused about the manufacturer saying there're going
to be some...

Think a moment. As the back of the blade is pressed occasionally against
the thrust bearings (what we're discussing), it peens the edges a bit, like
turning the edge on a scraper. Since it flexes and such, pieces apparently
develop a case of stickout, smacking the ceramics as steel on flint.

If you were ever a scout, you remember that sparks ignite tinder, which is
used to ignite kindling, etc.

The normally self-extinguishing dust - because it's got poor access to
oxygen - can ignite a chip or coarse piece of dust which burns hotter
because there's oxygen to more surface area, which can ....

George wrote:

....
Think a moment. As the back of the blade is pressed occasionally against
the thrust bearings (what we're discussing), it peens the edges a bit, like
turning the edge on a scraper. Since it flexes and such, pieces apparently
develop a case of stickout, smacking the ceramics as steel on flint.

Hmmm...as you can tell I've never used the ceramic guides nor
bearings...if they behave as you say (and I've no reason to say
otherwise) I'll agree...don't seem like a good idea at all. I've never
really seen a problem w/ the roller bearings on mine...

"Duane Bozarth" wrote in message
...
George wrote:

...
Think a moment. As the back of the blade is pressed occasionally
against
the thrust bearings (what we're discussing), it peens the edges a bit,
like
turning the edge on a scraper. Since it flexes and such, pieces
apparently
develop a case of stickout, smacking the ceramics as steel on flint.

Hmmm...as you can tell I've never used the ceramic guides nor
bearings...if they behave as you say (and I've no reason to say
otherwise) I'll agree...don't seem like a good idea at all. I've never
really seen a problem w/ the roller bearings on mine...

You will, eventually. Though the upper is normally mounted on an eccentric
on the Delta and clones, the lower is not, and doesn't always rotate under
pressure from the blade. Cut enough wet wood for turning, seize the
bearing, and sparks will fly, bearings will score.

Hmmm...as you can tell I've never used the ceramic guides nor
bearings...if they behave as you say (and I've no reason to say
otherwise) I'll agree...don't seem like a good idea at all. I've never
really seen a problem w/ the roller bearings on mine...

I have been using them for 4 years or so with no problems. almost a year without
a dc. I never had any problems with them. but maybes it is the blades I use.
I had ruined two sets of roller guides with ipe dust. it would clog them up.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

George wrote:

....

You will, eventually. Though the upper is normally mounted on an eccentric
on the Delta and clones, the lower is not, and doesn't always rotate under
pressure from the blade. Cut enough wet wood for turning, seize the
bearing, and sparks will fly, bearings will score.

Under those circumstances, no, I won't... (I don't work green wood
and so far haven't done any turning since high school although I would
like to get a lathe eventually).