Sanding

[rickets]

This is a call out to those who are as anal as can be when it comes to sanding.  This hasn't been a random occurance, but one I have been just dealing with. 

I always start out with 80 grit paper.  It's no different with my half sheet, dts, ro sanders.  It always leaves random swirl marks on the surface.  I try and get it out using 100 then 120, but I was told that after 80 grit, your really just starting to polish.  Seems true too. 

I've tried the variety of hand pressure on the machine; using only new, unblemmished sheets; different machine speeds.  I am using saphir and brilliant abrasives. 

I took a look at a variety of how to's clips also.  I'm dumbfounded.  Sooner or later, a customer is going to reject a piece.  I'm straight up with the customer.  I show them the piece and tell them to take a good look at it before going home with it.  Not once have they made any question of the swirl marks, but it's just killing me!  Help!

 

[Kev]

I wouldn't be using Saphir for anything but material removal and Brilliant is for stripping for starters ...

This is bare timber, right? I'd be looking to Granat or Rubin if you're finishing.

I've never tried to work up from an 80 in Saphir or Brilliant on bare wood - not something I'd do.

Others may think differently.

 

[Bob Marino]

Couple of things to consider. Why do you feel the need to start
All projects with 80 grit paper? 80 grit is a fairly rough grit. Also, saphir is
Not the paper of choice for most woods; rubin, brilliant or Granat
Are much better choices. Saphir is made for the down and dirty
Stuff, not for furniture grade wood. Finally, the consensus is that
You can safely go to 180-220 before any worry about polishing the wood.

Bob

 

[Jesse Cloud]

Good advice above - try Rubin or Granat.

100 grit gets out the 80 grit marks, but then you have 100 grits marks that are still quite visible.  So go next to 120, 150, 180, and 220 if you think you need it.  Put a slanted light on the piece and see if any marks still show.

Just for grins, here's how I was taught to sand.  Mark lines across the piece, as long as you have lines, the piece is not flat enough to sand everywhere.  Keep sanding nearby until the marks disappear.  Don't use hand pressure, let the machine do the work.

Sand first with the grain, then across the grain, then across in the other direction, then with the grain.  Keep the sander moving, but go slowly.

Before applying finish, rub some paint thinner on with a rag, any remaining marks will show up like grand canyon.

Good luck and let us know how it goes.

 

[Scott B.]

I agree with Bob, that 80 grit might be too aggressive to start with in alot of situations. It will depend alot on species of wood. Sanding 80 on pine is a very different thing than on oak.

I use all the different abrasive lines to an extent and find Granat to be the most forgiving for finish sanding. I think it is critical to eliminate pressure on the tool entirely. This only increases friction which compresses dust particulate between the abrasive and the surface before they can be extracted, which causes momentary load (even if you dont see sticky build up on the abrasive) and can causes swirl. With the right grit, extraction setting and motor speed on the tool, there is a sweet spot on every one of these sanders where they will just sit and float. I was just doing this with an RO the other night for kicks. Even in gear driven mode, you can float them with just a little guidance for them plug areas as a fulcrum.

However, in more agressive applications where there is some material removal or even just mill glaze eradication on the initial 80g pass in gear driven, its not unusual to get a scratch pattern. There should be no scratch pattern at all in orbital mode if you are running the tool in a balanced way with proper grit and settings.

One good test that we use on stain grade or clear finish sanding is, if in doubt, one good check and balance is to wipe the surface with a thinner rag. This will replicate finish and expose ANY scratch pattern in the grain so you know what you are looking to eliminate in the next grit step.

Also, it is pretty rare (for me) to be in gear driven mode for finish sanding when the grit is higher than 80 or 100. These are critical concepts and it is important to remember that sanding with Festool is different from sanding with any other tool, in the sense that you can back off and literally let the tool do the work. The less you interfere, the better the tool does.

 

[rickets]

Sorry, but I'm using rubin.  I was also told to start with 80 grit because that's the only time your really removing material.  Anything higher than that, your just taking out the scratch marks of the previous grit. 

It's also happening with my half sheet sander too using 3m sheets.  Am I moving the sander too fast?

 

[MrToolJunkie]

All paper removes some material, it is just how much..80 grit removes more than 180 grit, but you could sand for a long, long time with 180 grit and eventually sand defects out of the wood -- this would not be efficient at all and you would go through a lot of sheets, but it is possible.  Starting with a coarser grit removes material faster, but it will leave deeper scratches.  Going to the next grit works to make those scratches disappear and then you are left with scratches from tha paper...this goes on with each grit you move up.  When you are at 220 you are removing scratches left by 180.  The finer grit papers remove very little material and really starts to polish the wood, but you are still removing some material.

I agree with the pencil line trick -- this helps ensure that you are not oversanding in certain areas and missing other areas.  I will typically start with 80 grit removing milling marks and surface imperfections so that I can spend less time with higher grit papers and this works for my sanding wrokflow.  Sometimes I will start at 100.  If I use a hand plane, then I might jump to 320 just to smooth any imperfections from the hand-plane, but not always.

Hope this helps.

Scot

 

[rickets]

Looks like Ive been doing things a little different from what I'm supposed to do.  From here on in, ill definitely let the tool do the sanding.  I also think I'm moving the machines too fast, so that's why I'm getting the swirl marks.  Also, I thought we're supposed to use the gear drive for platin grits.  Thanks for the input guys!

 

[Scott B.]

Rick

Speed is kind of a non issue. Sometimes you get better results when it is slower. Its most important to be responsive to what the sander wants. Your job really is just to guide it, keep it balanced, apply no pressure and work with it as it floats around on the piece.

I've posted this in the past, but here is an example of some Rotex float action with one hand control during some fairly aggressive stock removal. Same applies in fine finish sanding, just a different stage on the surface.

Festool RO125 in Rotex Mode: One Hand Operation

 

[rickets]

MAN I WISHED I could just shadow you guys at your shop.  I'm really just self taught. 

 

[oradba69]

Rick

Speed is kind of a non issue. Sometimes you get better results when it is slower. Its most important to be responsive to what the sander wants. Your job really is just to guide it, keep it balanced, apply no pressure and work with it as it floats around on the piece.

I've posted this in the past, but here is an example of some Rotex float action with one hand control during some fairly aggressive stock removal. Same applies in fine finish sanding, just a different stage on the surface.

Festool RO125 in Rotex Mode: One Hand Operation

I wish I could get my RO150 to run like that. I dont consider myself a complete newbie with it since I have had it for a year or two. My problem is the sudden jerks it exhibit.
I have turned down the vacuum, adjusted the speed up and down but I cant get it to run constantly smooth(It is better in orbital mode). I see even in your video it sometimes make a small jerk. Mine is about 3 times more violent.  :'(

 

[nickao]

I think what he was saying about the 80 grit is that anything above 80 really just follows the surface of the item and takes off so little wood "it seems" to only remove scratches and IMO, he is right.

To flatten some of my items I start with a 40 grit. There is no way a 100 grit would flatten the discs, not even if  sanded for 2 days. It would just follow the humps and dips sanding out the little scratches. I would end up with a really smooth disc with humps and valleys. In that sense the higher grits don't remove material, not in the sense to make an item flat. Of course using a 40 for other items that are already nicely constructed and flat would just create a lot of work for nothing. Depending on the stock there are project that I can start with a 120. And I am one that never goes to the higher grits, 220 max at the most. I like the woods to retain there natural appearance and for my personal aesthetic going above that just gives a plastic type look to the finish. I guess some turning items can take the super high grits.

I would suggest to the poster that can not control the sander to put on the hard pad immediately. I only use the hard pad, for my work it makes all the difference in the world.

Some people can never get the hang of the RO sanders, I can not live without them. It takes practice and it's tough to tell how much a person really uses the sander when they say that they have it a year. Is that sanding 3 hours a day or two hours a month? I believe for some people to grasp this sander it takes a good 20 hours of actual sanding. Think about it, thats a lot of sanding!

 

[fdengel]

You need to keep a firm horizontal grip on the sander, but not apply that firmness vertically to the wood... does that make sense?

(This obviously assumes the workpiece is laying flat and the sander on top of it...)

 

[rickets]

I tried the no pressure technique, but still got some swirls.  Just tried to guide it and when it did jerk, I- as much as possible- just tried to apply horizontal pressure to the RO.  Much better though.  When I sprayed on the lacquer, there are no indications of sanding what's so ever.  I still need much time behind the sander, but I do think I could get the hang of it.  I would also like to say that I was moving over the project no faster than a foot/sec at the fastest. 

 

[semenza]

I tried the no pressure technique, but still got some swirls.  Just tried to guide it and when it did jerk, I- as much as possible- just tried to apply horizontal pressure to the RO.  Much better though.  When I sprayed on the lacquer, there are no indications of sanding what's so ever.  I still need much time behind the sander, but I do think I could get the hang of it.  I would also like to say that I was moving over the project no faster than a foot/sec at the fastest. 

I know you said that a foot per second is the fastest you were going but what was the slowest?  I would be shooting for more like a couple inches per second.

Seth

 

[rickets]

Ok, so on my recent project, I've moved the RO150 no faster than 2 inches per second on the work.  I also started on 120 grit, but I'm still getting some swirl. Dunno, because I had a construction buddy come over and take a look.  I shined a light and everything.  He couldn't see what I was seeing.  I still see it, though very miniscule.  The sanding is much much better, but still seems like it could be better.  Guess time will tell.

 

[Stone Message]

If you are using a Rotex machine then start at the lower grits and work upwards. When you start with a grit use rotary motion and then finish with random motion. Then move on to the next grit and repeat. The rotary motion at the start will remove the swirl from the previous random session with the lower grit.

I learnt this at a show when a brilliant guy from Festool UK demonstrated the right way to sand with a Rotex. I have used this method ever since and had no problems. I did make a video about once upon a time.

Peter

++ Just found the link for the video....

 

[RONWEN]

Great demo Peter!  [thumbs up]

 

[ccarrolladams]

What an interesting demo of the RO90DX.

See, there apparently is a difference of opinion between the Festool USA trainers Steve Bace and Brian Sedgeley and the representative of Festool UK.

In Festool USA classes the preferred technique is to lightly grasp the knob directly above the rotating pad in one hand while the other hand supports the handle/hose connection to prevent droop and ensure the pad is level with the work.

The downside to the technique demonstrated is that nothing is keeping the pad level. The tendency will be for the pad to dig in at the leading edge away from the handle.

Of course we all sand in different ways, so by all means give both approaches a decent try.

 

[RONWEN]

What an interesting demo of the RO90DX.

See, there apparently is a difference of opinion between the Festool USA trainers Steve Bace and Brian Sedgeley and the representative of Festool UK.

In Festool USA classes the preferred technique is to lightly grasp the knob directly above the rotating pad in one hand while the other hand supports the handle/hose connection to prevent droop and ensure the pad is level with the work.

The downside to the technique demonstrated is that nothing is keeping the pad level. The tendency will be for the pad to dig in at the leading edge away from the handle.

Of course we all sand in different ways, so by all means give both approaches a decent try.

I would say that "Peter's" grip provides more control while doing heavy sanding and the FestoolUSA grip better balance in the final stages.