On 7/21/2014 11:13 AM, Larry Blanchard wrote:
On Mon, 21 Jul 2014 10:54:06 -0400, Mike Marlow wrote:

Leon wrote:


Actually the direction that you move the sander, ROS or finish sander,
is more important.

I have to disagree with this statement Leon. It has nothing at all to
do with direction. I would say that it has something to do with the
speed at which you move in any direction - so as to allow the orbital
action to do its thing, but most certainly - not to do with the
direction. It's orbital - direction has no meaning. With a finish
sander - ok - might agree on that point.

Since I seem to have triggered this discussion, I'll chime in.

I agree with Mike. I've never had a problem with cross grain scratches
using my ROS. Sure, you can see scratches in coarser grits, but they're
orbital, not directional. If Leon is seeing scratches most likely he's
either not going to a fine enough grit, he's bearing down too hard, or he
has an orbital sander, not a *random* orbital sander.

I can't state that there's no ROS that will do what Leon's does, but I
can state that mine (an old Bosch) doesn't.

Can the mechanism in an ROS fail in such a way as to eliminate the
randomness?


FWIW I used a PC Right angle ROS starting in the late 80's and used it
until going to the Rotex 5~6 years ago.

Revisiting the ROS action, yes it is a random action but if you are
going cross grain you are still moving the cutting edges of the grit
across the grain. Yes the ROS is better than a regular "non random"
orbit sander but I can't get away with what I see if I get up close and
personal. I very very very seldom have ever used a ROS as the last step
for sanding regardless of grit.

Now having said that I too have used a Bosch ROS. By comparison it was
much less aggressive and beyond noticeably slower than both the PC and
the Rotex in ROS mode so perhaps some ROS sanders don't display that
scratch pattern but IMHO the whole purpose to use a ROS over a finish
sander is to speed up the sanding process.