Sanding: Skipping grids and mixing different abrasives

[threesixright]

Hi,

Just posting here, since the "Finishing and Painting" does not seem to get a whole lot love  [crying]

Basically 3 questions about sanding.

1. I understand the finer you get the easier you can skip grids, makes perfect sense. I'm wondering is there any "rule of thumb" what jumps (in grid size) you can make while getting a great finish?

2. Can you mix different abrasives as long you follow the grid ( So 60, 80, 100 for Paper X, then 120, 150, 180 for Y, etc.)?

3. Anybody experience with stained wood, which paper would be best (im just thinking to start with Granar 60)?

Thanks a whole lot!

 

[Alanbach]

Personally I might not skip 80 if I started with 60 but other than that I skip at least one grit all of the time. Festool produces a huge range of grits in Granat which is the type that I mostly use. No way that I would go 220,240,280,320,360,400. Maybe 220,320,400 if I was going to go that high. I use compressed air and a tack cloth between every grade (even with Festool dust collection) and I keep my work area very clean to avoid contaminating the workpiece with grit or debris from a prior grit. I also use raking light to check for visible scratch patterns.

As far as mixing types of festool sandpaper I usually don’t worry about it. On the rare occasion that I can’t get Granat and I have to fill in with something else I just do it. The most I might do is squeeze an extra grade in as I move up just to make sure that I am back to a progressive scratch pattern that I trust.

Can you clarify your question about stained wood? Do you mean to remove a stained surface via sanding? If so I would say that there is no rule of thumb as different stains penetrate different woods differently. If there is a rule I would say use the finest sandpaper grit that you can without working yourself to death. No reason to go down to 40 when 80 or 100 will do the job.

My final note would be about Festool finish sanders. Festool’s line of sanders is more specialized than almost all others available here in the US (where I am). If you have the right sander for the job matched with their correct abrasives for the job along with their variable suction vacuums you should have very little (if any) trouble with preparing a surface for a finish. This equipment is very very good at what it does. Let it do the work. If you are working really hard something is probably wrong.

 

[sancho57]

It all depends, Some times Ill go from 100-220. as long as the finish is the way want I dont stress it. Now If I find I have swirl marks Ill go to up the grits to get rid of them

 

[threesixright]

Can you clarify your question about stained wood? Do you mean to remove a stained surface via sanding? If so I would say that there is no rule of thumb as different stains penetrate different woods differently. If there is a rule I would say use the finest sandpaper grit that you can without working yourself to death. No reason to go down to 40 when 80 or 100 will do the job.

Thanks! here I posted similar question, with picture of the "subject". These are beams, not painted but stained (not sure if thats the correct naming). Some type of oil I think. Not sure. But definitely not paint.http://festoolownersgroup.com/finishing/sanding-stained-wood-with-rotex-125-which-abrasive/

 

[Alanbach]

Hard to tell from the pics but it looks pretty smooth to me, which is good. If it’s rough then you are going to have to sand it all down smooth in order to get rid of the stain altogether?

So if it’s me, (and if it’s smooth) I find the most inconspicuous place in the room and I do a small test patch. MAybe just one pass wide (5”) and no more than a foot to a foot and a half long. Maybe start with 120 and see what happens. If you have to go back and get a lower grade paper it won’t matter since you will always be able to use the 120 on other projects. Once you get it to it’s true color then you can go 150, 180, 220 and then finish the test patch to see if you are happy. If you want to stay as close to the wood’s natural color without darkening it I would recommend a water based poly like the one made by General finishes. It comes in flat, satin and semi-floss. This is going to be a lot of work so I hope that you like the color of the wood underneath.

 

[Corey P.]

For me, it depends on the wood.  If I go too high a grit, I might glass over the wood, making it harder to take a stain.  If it's visible and especially touchable end grain, I go up to 320.