Turning Sander on while touching the workpiece?

[AlexThePalex]

Alex, there was nothing in my posting to warrant your attitude and hostility. When a simple posting such as my previous one gets you this fired up, it leaves me with no desire to continue the discussion.

You call that hostility?

Wow! I am quite surprised.

And then there was me reading exerts of discussions between you and Matthew in old threads. I think the word hostility had a whole other stretch there. Or in the last thread about Festool America's website.

In the mean time, I just explained why I think, with others, like PC's engineers, why there is another reason for the pad brake.

If being shown wrong is hostile to you, well, fine. We all got egos to maintain.

 

[ForumMFG]

Alex,

I think some of the problem might be the fact that this is a conversation over the internet and not in person.  We can't hear your tone of voice and because of that, your message came across the way it did.  I certainly would of felt the same way Rick did.  It's just a misunderstanding so kiss and make up and stop bashing the man because your last message sounded the same way.  Don't take any of this the wrong way, just trying to get some love in thread. =)

-Dave

 

[Rick Christopherson]

I was really looking forward to what Rick had to say.  After reading these posts, I started thinking "have I been sanding the wrong way all this time or not". 

Starting the sander on the workpiece is not really that big of a deal. Yes, it will leave some marks as it spins up, but those marks will be trivial as long as you continue sanding after startup. So from that perspective, it makes very little difference. The pad brake exists so you can start the sander off the surface if you wish.

Before making my next point, I want to state that I have not used any of the Festool sanders, so I cannot comment on how this information applies or not.

Quite a few years ago I performed a very in-depth product review of about 40 RO sanders, including examination of the resulting scratch patterns using a staining fluid and a low power dissecting microscope to count visible scratches, and identify the classification of scratch types. (I used to be a NIOSH and PAT certified microscopist for microscopic counting of fibers.)

Pad brakes (I can't believe I misspelled that in my previous post) tend to remove the "randomness" from "random orbit". The more effective the pad brake, the less random the motion of the pad. Porter Cable is the worst offender in this area because their O-ring style pad brake is extremely effective in stopping freewheel rotation (I don't know if they are still using this design).

I took several RO sanders with pad brakes and examined the scratch counts both with and without pad brakes installed. The results were absolutely conclusive in that the scratch count was higher and the scratch type more pronounced when the brakes were functioning. The finish was significantly improved when the brakes were removed.

Don't do this with a Festool sander because they were all developed after I performed this test, so I cannot comment on them. However, if you are using one of the small palm sanders and you habitually prefer to start the sander while on the workpiece, then you are better off removing the pad brake mechanism.

Some woodworkers mistakenly believe that when they see the sanding pad spinning rapidly while on the workpiece (not the same thing as freewheeling while in the air) that they are increasing the scratches of the finish. As a result, they tend to change their technique to reduce this spinning, such as applying more pressure. This is incorrect. There will be more random motion in the path of the pad when the pad is allowed to spin at its natural rate, and that includes artificially slowing the pad rotation down with a pad brake.

When the motion of the pad is random, the shape of the scratches will be fairly straight and shaped like a narrow "Y". When the pad is constrained to be less random, the shape of the scratches will be circular, and very similar to a "Q" with a double tail. It is these round "Q" shapes that are much more visible in the finished wood.

Any time that you feel the sander jump, stutter, or wobble, you have just left behind these "Q" shaped scratches. Sand with a light pressure in a smooth motion, not too fast, with smooth transitions as you change directions. The rotational speed of the sanding pad should be several revolutions per second and should be fast enough to be a blur.

 

[ForumMFG]

Wow Rick!  Sounds like you had a really cool previous job.  And wow, I just learned so much about sanding!  Thanks a lot Rick, I really enjoy reading what you have to say all the time.

-Dave

 

[Rick Christopherson]

Wow Rick!  Sounds like you had a really cool previous job. 

I used to be an editor with American Woodworker magazine. Back then, they wanted to go head-to-head with Wood Mag for product reviews, and brought me in to do that. But then they changed their mind on the depth and complexity of reviews, and chose to go with less technical reviews.

 

[EcoFurniture]

Thanks guys!

 

[Michael Kellough]

In my experience, with a Festool vac you can start a sander on the work because you have time to start moving the sander before the vac kicks in. With a Fein vac (or others that start immediately) you need to have the sander moving by the time you switch the power on. The worst situation is a slow moving abrasive under pressure. For that reason it seems to me that pad brakes are intended to allow you to stop the sander while it is on the work. They don't seem to have much affect on the start-up process.

I've used RO sanders since the first PC electric version came out about 25-30 years ago (don't have much experience with pneumatic RO sanders). Some of my sanders have a brake and some don't but my process is always the same. To start I lift up enough to allow the pad to spin up quickly and I immediately start moving the sander across the surface before the downward pressure from the vacuum kicks in. To stop I lift a little and hit the switch (all the while moving the sander across the surface) and steer the sander off the work before it begins to spin down.

 

[Neill]

In my experience, with a Festool vac you can start a sander on the work because you have time to start moving the sander before the vac kicks in. With a Fein vac (or others that start immediately) you need to have the sander moving by the time you switch the power on. The worst situation is a slow moving abrasive under pressure. For that reason it seems to me that pad brakes are intended to allow you to stop the sander while it is on the work. They don't seem to have much affect on the start-up process.

I've used RO sanders since the first PC electric version came out about 25-30 years ago (don't have much experience with pneumatic RO sanders). Some of my sanders have a brake and some don't but my process is always the same. To start I lift up enough to allow the pad to spin up quickly and I immediately start moving the sander across the surface before the downward pressure from the vacuum kicks in. To stop I lift a little and hit the switch (all the while moving the sander across the surface) and steer the sander off the work before it begins to spin down.

Michael,

So what you are saying is that you start the sander spinning off your workpiece regardless of the type and brand of sander you are using.

Neill

 

[Michael Kellough]

Michael,

So what you are saying is that you start the sander spinning off your workpiece regardless of the type and brand of sander you are using.

Neill

Not fully off the work. I just take some of the weight off so it spins up faster.
Seems to me it avoids grinding to a start that way.

 

[Brice Burrell]

Just so everyone understands what's happening when you start or shut off a RO sander on the work surface, the orbital action kicks in almost immediately then the rotation of the pad follows a short time later. The reverse is true turning off the sander, the rotation stops first then the orbit. As Rick pointed out it's the rotation of the sanding pad that makes the sanding pattern random. For a few seconds on start up and shut down you don't have the rotation, only orbital action so you more or less have an orbital sander. An orbital sander not moving or moving very little is a surefire way to get swirls marks. So with the sander on the surface during start up/shut down it's no big deal on start up, just sand any swirls out but on shut down you may not came back to sand them out. My two cents. 

All my (electric) sanders have a sanding brake so I start them off the work piece and carefully set them down to start sanding. I also carefully remove the sander from the piece before switching it off. My take on sanding brakes is this, it's ok to start off the piece if you are careful setting it down. Or you can start it on the piece, you may get some very minor scratching but since you've just started sanding you can easily sand a blemish out. I would think it's better practice to remove the sander from the piece before turning it off as a general practice since any possible scratching may not get sanded out. Of course each individual's own technique will likely work, getting good results from ro sanders is almost a no brainer (probably even for Dave  ). 

 

[wnagle]

Thanks to everyone's expert input!  And excellent summary Brice! 

As per usual...

 

[ForumMFG]

Hey now Brice =)

 

[okami]

Hello

When I owned a RO150, I removed pad, and it did improve the scratch pattern (but not enough to keep it ;D ) I believe the pad was restricting the random movement, as Rick mentioned.
With the pad on , the scratches were the shape Rick mentioned also.

I now use a Metabo sander, and it performs much better.  I don't know whether it has a pad or not (it probably does), but I can start on and off without causing problems.  When I start off the work, I bring it down like a plane landing.  As soon as it glides down, the sander it moving along the work.

Now Pneumatic sanders are much nicer to use compared to electric IMHO.  If You have a big compressor, You won't look back at electric.  Unfortunately, I don't have a big enough compressor right now so I'm stuck with electric :-\
Cheers!
Okami

 

[ForumMFG]

It would be nice if someone from Festool would chime in on this matter.  I would like to know if we should remove the brake for a better finish?

 

[RONWEN]

I've had a Metabo angle grinder for several years and it's a great tool.  Based on Okami's input, I purchased the same Metabo sander that he is using.  It does a very nice job, I'm very pleased with it & I need to look into other Metabo sanders.  Those Germans...

Hello

When I owned a RO150, I removed pad, and it did improve the scratch pattern (but not enough to keep it ;D ) I believe the pad was restricting the random movement, as Rick mentioned.
With the pad on , the scratches were the shape Rick mentioned also.

I now use a Metabo sander, and it performs much better.  I don't know whether it has a pad or not (it probably does), but I can start on and off without causing problems.  When I start off the work, I bring it down like a plane landing.  As soon as it glides down, the sander it moving along the work.

Now Pneumatic sanders are much nicer to use compared to electric IMHO.  If You have a big compressor, You won't look back at electric.  Unfortunately, I don't have a big enough compressor right now so I'm stuck with electric :-\
Cheers!
Okami

 

[Holzhacker]

My 2 cents ... starting on or off wood pretty much irrelevant. If you're going to sand the piece anyway presumably one is paying attention to sanding out any swirls and isn't putting heavy pressure on the sander during startup.  However, I do always stop OFF wood. From my experience stopping ON wood does ruin whatever finish I've worked so hard to achieve.

 

[Brice Burrell]

It would be nice if someone from Festool would chime in on this matter.  I would like to know if we should remove the brake for a better finish?

Dave, I can't imagine Festool adds a sanding brake, spending the money and taking the time to put them on the sanders, then recommended you remove them. A properly functioning sanding brake isn't going to adversely effect your finished results.

Most of us are familiar with the break in period for Festool tool, this break in is especially important for sanders. We most commonly talk about the carbon brushes seating during this period but that's not all that is happening. The sanding brake is also breaking in, as it does the sander's pad will be allowed to spin a little faster and this can produce better results. In some cases a new sander's brake may be braking the pad's rotation a little too much, combined this with a motor that might not be producing full power until the brushes seat and the results may not be as good they will be after the break in period.

This discussion has mostly centered around the sanding brake as it relates to safely setting the sander down on the surface but there is so much more to it that that. On a random orbit sander the pad's rotation is an important factor. If the rotation is too slow the scratch pattern won't be very random and you'll be left with results much like an orbital sander. You might experience this if your sander is new and sanding brake isn't broken in, if you have excess suction from your vac or you are applying too much downward pressure on the sander. Too fast of a rotation and the grit particles may not be able to cut effectively so you'll get some burnishing of the surface (remember we want to shear (cut) the wood fibers off when sanding not burnish the surface.) This can happen to sander without a brake or a warn brake. The brake helps controls the speed of rotation to optimize sanding when working correctly not detract from it.     

 

[ForumMFG]

Honestly, I kind of figured that out myself a long time ago.  Some people are saying one thing and then another.  I guess I should have said it differently such as, would removing the break increase the effectiveness.  Who knows right?  It's there for a reason but there could be something more to it than just slowing the pad down.

 

[RONWEN]

I watched most of the Festool RO demonstration videos, in most cases (if not all) the RO was started up off of the work surface & then applied to it.  The exception seemed to be where they applied polish to a buffing pad -- the RO was then started while in contact with the work surface.

 

[greg mann]

Just to muddy the waters even further:

I have seen to demonstrations using the Rotex to bring a rough sawn board to a surface ready for finishing. In one case, by Brian at Festool, various grits and grades were used sarting in Rotex mode and working through several of the rougher grits and then switching to ROS mode to finish. Beautiful results. In another demo, also by a Festool rep, the machine was left in Rotex mode all the way through the process from start to finish. Beautiful results. In neither case was a magnifier used so I will not claim they were exactly equal, but they were both acceptable to all parties in attendence.

It would seem that the notion of using the Rotex mode, which maintains a constant rotation in addition to the orbits, would support Rick's assertion that it is useful and effective to make sure there is adequate rotation of the pad. There seems to be a consensus that this rotation is exactly what makes the action of the sander random. The addition of the pad brake could really be seen as one way to control (and limit) rotation speed while the Rotex mode could be seen as a way to control (and invoke) rotation.

This has no direct bearing on which start and stop technique is best but does speak to the broader question of scratch pattern and control. I would also like to hear what Festool thinks, from a sanding philosophy perspective as well as how those philosophies are reflected in their tool design.