Dave and All,

thanks for continuing the discussion.


For those of you who are doing some of these things like Dave and Patriarch,
can you see from the photo link up there at the other post if the roundover
bit used is something off the shelf or maybe supplied with my Canadian
friend's spin saw kit? Mine is not the same. I have sent a mail to the guy
but didn't get any replies yet... it's vacation season.


Anyway, today from the added messages I feel a little bit better about
keeping the thing. But still I'm hoping for more discussion.


And yes, what I'm doing is very casual: what I have is a flat pack of
baltic birch plywood to make 2 desktop speakers for computer use. The
longest length is 16 inches for roundover. The cutouts for this project
will be made with a 3" fly cutter (hole saw) and I am wanting to do a rabbet
to flush mount the driver plus a chamfer on the back side for relief of the
"backwave".

So what are the chances of significant kickback from the tool?


As you can see from the picture the guy used the roundover for a lot
of pieces. I re-read the whole thing and no mention is made of
the job being really slow.








On 14 Jun 2004 15:31:36 GMT, Dave Hinz wrote:

On Mon, 14 Jun 2004 04:07:41 +0000, Robert Bonomi wrote:

The bad news -- That tool, and *any* similar one, regardless of manufacturer,
are the WRONG THING for the type of job you propose to undertake.

If there's a finished surface involved, yes. If he's going to cover it
with black carpeting or something, the circle jig that comes with the
rotozip does a reasonable job.

Spiral saws are designed to work in _brittle_ materials -- ones that 'powder'
when 'hit' with a sharp edge. They're _great_ for drywall, and, as long as
you're careful about heat build-up, you can do amazing things on ceramic
tile, too.

I used mine this weekend cutting some 1/8" plexiglass, both straight cuts
against a clamped straightedge, and a circle-cut (freehand for non-critical
circle-ish shape).

For cutting wood, on the other hand, they are 'medium dreadful', to put it
charitably.

Hm, I find it about as usable as a saber saw.

The bits don't have big enough 'flutes' to clear the wood chips, so they
are *very* slow cutting, Like only a few (maybe 5) _inches_ per minute,
in 3/4" stock, *IF* you can keep from breaking the bits.

You're using the wrong bit, then. Lots of options. Sounds like you
were using a tile bit on wood, maybe?

Due to the small diameter, they don't have the structural strength for the
side pressures, and you'll break bits *real* often. Like, if you're lucky,
you'll get 4-6 _inches_ of cut in 3/4" material, per broken 1/8" bit. Don't
even _think_ about using the standard 1/16" ones.

Mine came with 1/8" bits, never saw a 1/16" bit. Sure you're talking
about a RotoZip? Don't get me wrong, I'm not saying that it's high-art
of toolmaking or anything, but what you're describing isn't consistant
with my personal experience.

Tool edge speed aside, for the fwe times I use it, it works great.
Like anything else, using the right bit for the job is critical.

Dave Hinz