correct use of a random orbital sander; general and Festool specific

Hello All, The only ROS I have used with any amount of time are the two Festools I own; a 6 inch Rotex (about 3 years old ) and a 5 inch finish sander. When using the Rotex as a ROS or the 5 inch I notice that the pad spins rapidly when minimal downward pressure is applied. If I bear down on it the pad will slowly rotate, much like a second hand on a clock. Which is the best way to use these machines? Am I risking sander failure if I push too hard? Am I causing whirling if I let it rest by gravity alone? Also, what vaccum setting do you use? Do you vary the suction depending on the grit being used or do you keep it constant? I do notice whirling with the Rotex (6mm oscillation, I think) when sanding with 180 grit and larger but I can make that disappear with finer grit or by going to the 5 inch finsih sander (2mm oscillation). Any comments or criticisms are welcome. Marc (taking a break from sanding a 84 x42 Cherry door; 6 inch stiles, 51/2 inch rails - top, bottom and middle, all 8/4. 4/4 T&G boards as filler, 6 across. It's a sliding door for my neighbor's wine cellar.)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Are you using the 'aggressive' setting? That setting on the Rotex WILL rotate. The 'fine' setting shouldn't rotate too much. Speed at # 5 is best for wood, I find. The vacuum setting on max. always.... and blow off the work between grit changes.
On raw cherry, I'd start with 180 on 'aggressive' if it comes out of the planer reasonably clean. If the planer leaves a lot of 'ladders', I'd hit it with a 120 grit belt first. (and quickly, no loitering)
Then, after 180 on 'agg', I'd flip over to 180 on 'fine' then 240 on 'fine'. 320 is optional, but seldom required.
Hey, that's just me. I seldom use a finish sander anymore. Only if I need to get into a corner.
r
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The only correction , and a small one is to reduce vac to about 1/2 speed when using grits over 320, per manufacturer, this reduces the aggressiveness of the paper causing a better sanding job. For general sanding raw wood or a painted surface, wide open.
Ken
wrote:

Are you using the 'aggressive' setting? That setting on the Rotex WILL rotate. The 'fine' setting shouldn't rotate too much. Speed at # 5 is best for wood, I find. The vacuum setting on max. always.... and blow off the work between grit changes.
On raw cherry, I'd start with 180 on 'aggressive' if it comes out of the planer reasonably clean. If the planer leaves a lot of 'ladders', I'd hit it with a 120 grit belt first. (and quickly, no loitering)
Then, after 180 on 'agg', I'd flip over to 180 on 'fine' then 240 on 'fine'. 320 is optional, but seldom required.
Hey, that's just me. I seldom use a finish sander anymore. Only if I need to get into a corner.
r
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Why do you want to push hard? We buy power tools to make work easier and it is designed to work with light pressure.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hello Edwin, It's not that I want to push hard, but I notice the pad behaves differently when there is minimal pressure vs. pushing down on it. There is more circular motion with little or no pressure and I'm wondering if this is the way the sander should be used. I thought that more circular motion would leave swirls and strictly oscillating would make a better finish.
And to Robatoy, my Rotex does not have a fine or aggressive setting, but it does select between rotating or oscillating. Is this what you are referring to or does your- later model, I presume - Rotex have those featured settings?
Anyway, the door is sanded and my lovely wife applied the wipe on poly. Soon it will be assembly time. Read you all later, Marc
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hello Edwin, It's not that I want to push hard, but I notice the pad behaves differently when there is minimal pressure vs. pushing down on it. There is more circular motion with little or no pressure and I'm wondering if this is the way the sander should be used. I thought that more circular motion would leave swirls and strictly oscillating would make a better finish.
**************************************
Pushing hard is more likely to gauge the wood rather than sand it to a nice finish. Use enough pressure to guide it, not force it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I have the Rotex and the Festool Finish sander. Both took some getting use to. With the Rotex in the less aggressive RO setting I dial down the vac so that it will float more easily same goes for the Finish sander. I found that with the vac dialed up that the sanders felt sluggish. I do back enough that it gets all the dust but dies not restrict movement. I do not press down harder with either sander other than enough to keep them up right and flat.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.