Small swirl patern

[mastercabman]

I am making a simple counter top.I'm using 3/4" maple plywood and i use maple edge tape for the expose edges.
I was sanding the top with my rotex 150 and i noticed swirl mark all over the surface.
Very small,about 1/8"- 3/16". I try to sand again with 400 g. and could not get them off.
So i decided to use the other side.But it has a small flaw on the surface that is very noticeable,so i flipped it again and used a damp cloth to wipe the surface (trying to raise the grain)and then try to sand it again.I got lucky,the swirls are gone.
So now I'm back in business.
But what caused those swirl marks?  Could it be dirt trapped between the work surface and sander?

 

[jimwho]

While this has never happened to me I just read about it in the 2009 catalog (see page 171). They have a tip that indicates to turn the suction on the "vac" down towards the turtle to avoid possible "swirl" marks. If you were using the vac maybe this is the reason.

Jim

 

[EcoFurniture]

Clean your workpiece between grits! To much down force created by the vacuum can also cause the swirl marks.  

 

[tbellemare]

'Spot on...

Try to adjust the CT so that the sander is loading the same with the vacuum as it is without it. Too much suction pulls the sander into the work piece and is the equivalent of leaning on it. You can hear the right adjustment of the CT.

Tom

 

[Greg_R]

Also, pushing down on the sander will cause the swirls.  Just let the weight of the tool do the work and make sure the vac is adjusted properly.  The circles are particularly common on hard wood like knots, compressed grain, and tropical hardwoods.  With proper technique you can avoid them.

BTW, the circles are the size of the random orbit pattern.  That's 1 grain on the sandpaper spinning around / scratching the surface.

 

[John Langevin]

Ditto the above comments on vac speed, downforce, cleaning. Were you getting any loading (corms) on the abrasive disc? If this happens you will get somewhat larger marks. With the Festool System you have the ability to accurately adjust all these parameters and optimize your results.