Sanding technique - Rotex 125

[Mavrik]

I'm sure this has been answered before, so forgive me for asking again.

I have a Rotex 125 ... which has the "coarse" setting; which the disk spins ... and the "orbital" setting for fine finishing.

If I have some rough-ish timber; what is the recommended sanding technique.
i.e. assuming I am starting with 50 grit paper on the "coarse" setting ... what is the best progression of paper ... and with which setting?

How small a difference in grit should there be between each paper change? And which setting?

Today I tried 50 on "coarse" ... then 50 on "orbital".
Then stayed on orbital on 80 ... 100 ... 120 ... 180 ... 220

Is this optimal?

I generally hate the sanding part, so the more efficient the better please
[big grin]

 

[Brice Burrell]

Sounds like you're on the right track.  What grit you start with depends on how rough the material is.  I use the coarsest grit in rotary mode and then switch it to ro mode to clean up and deep circular scratches.  Moving through grits without skipping grits is the best method and it usually the fastest too. You generally don't need to spend much time with each grit if you gotten off the good start in the coarser grits.

 

[Chris Hughes]

It depends on the hardness of the material you are sanding too.  I solid surface we skip a lot of grits.  Generally we would do 100, 220, 400, 600 and then polish.  The objective with sanding is to replace big scratches with smaller scratches and then with even smaller. 

I have found that often it is easier to get a more consistent surface by going slower and more methodical.  On solid surface generally with a ro125 I move about an inch a second and sand once left to right and then once front to back per grit.  Always remove the dust remaining on the surface before moving up a grit so that you are not grinding 80 grit particles in while sanding with 120.

I wish there was a class on sanding.  IMO it is one of the things that as craftsmen we screw up the most.  It would be about the most boring class ever second maybe to gluing 101 but I would love to understand what the different papers do on different hardness's, but then again I am a nerd.

 

[Brice Burrell]

I wish there was a class on sanding.  IMO it is one of the things that as craftsmen we screw up the most.  It would be about the most boring class ever second maybe to gluing 101 but I would love to understand what the different papers do on different hardness's, but then again I am a nerd.

I intend to grill Brian and/or Steve at the door and drawer class about future classes including of a sanding class.  I also hope to get them to talk about the Festool different abrasives on camera.  I'm going to ask if they have a piece of solid surface in Lebanon to demo on since I've never seen that process before. 

BTW, good advice on wiping down between grits, I should have mentioned that. 

 

[tbellemare]

Mavrik:

I would suggest that you use Rotex and then RO mode with the same paper through 100. Then, just use RO through 500. At 1000 & above, just use Rotex.

I agree with Brice about not skipping grits. With hook and loop abrasives, it is so easy to change grits that I think it goes faster to not skip grits. You only need to sand a little with each change because you're not trying to take out relatively big scratches with relatively small abrasive grains.

Tom

 

[mosez]

it is just a lot more expensive to stock up on all the different grits.
and what is actually meant by "skipping a grit"? i once heard, that as a rule of thumb you should not go up in grit more than double the current grit. so the grits that i have are 40, 80, 150, 240, 320. i do have a few 120 and 220 but i cant see any difference as opposed to using the others only. i second the part of doing the rough grits very thouroughly, thus making your life with the higher grits a whole lot easier.
so: what is "a grit" in terms of "you should not skip to many grits"?

 

[Brice Burrell]

it is just a lot more expensive to stock up on all the different grits.
and what is actually meant by "skipping a grit"? i once heard, that as a rule of thumb you should not go up in grit more than double the current grit. so the grits that i have are 40, 80, 150, 240, 320. i do have a few 120 and 220 but i cant see any difference as opposed to using the others only. i second the part of doing the rough grits very thouroughly, thus making your life with the higher grits a whole lot easier.
so: what is "a grit" in terms of "you should not skip to many grits"?

I think jumping form 80 to 150 is the perfect example of what not to do.  Removing 80 grit scratches with 150 is going to be far more time consuming than using 100 and/or 120 in there.  And, you more likely to remove all of the blemishes because you aren't going to say "screw it, it's good enough" after you've sanded for a while.

EDIT: I forgot to add, getting great results generally takes some time and it always costs money.

 

[mouppe]

I have the 125, and this is my general sanding technique. If the wood is really coarse, I use cristal 40 or 60, I forget which I have. Then I switch to Rubin 100, 120, 180. At 180 I switch to Random orbit mode and stick on a brilliant 220 and sometimes I follow with brilliant 320, depending on the finish I am using. For example, if I am using shellac, I stop at 220.

If you don't skip grits you will find that your paper lasts much longer as well as the other reasons cited above. It also makes sanding much faster.

Sanding is more of a science than an art, so there are no hard and fast rules. I am sure you will develop your own technique.

 

[ScotF]

Agree with what others have said to not skip grits.  I think it is generally OK to skip every other grit -- say going from 120 to 180 and skipping 150 if you need to; however, I find going through all of the grits to be more efficient and yield a better finish.  Wiping off between grits is also key as has been mentioned. 

Scot

 

[Kevin Stricker]

Starting with 40 grit can lead to problems some times.  Specifically you will sand up to 180 then wet the surface with mineral spirits and see some nice 40 grit scratches you did not get.  If you are using soft wood I find that starting with 80 is fine.  For hardwoods, I find that I need to at least double my sanding time if I start with 40 or 50.  To insure you get a good surface I will do a combination of Rotex and RO for all my lower grits up to 120, then switch to RO only from there.  If I start with 80 I will only do a 120 in rotex mode if I am worried I might have gotten a bit tippy.  With the 125 having good technique is the key to getting a good finish.  If you try to sand one handed you will likely be disapointed with the results.

 

[mosez]

of course i wouldnt start at p40 on board that is already probably 80 or at least 60. i only use the 40 to remove old coats if necessary.

 

[kswaby10]

Thanks for the suggestions guys.

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[AlexThePalex]

Starting with 40 grit can lead to problems some times.  Specifically you will sand up to 180 then wet the surface with mineral spirits and see some nice 40 grit scratches you did not get.  If you are using soft wood I find that starting with 80 is fine.  For hardwoods, I find that I need to at least double my sanding time if I start with 40 or 50. 

I completely agree. I really am not fond of grits below 50 or 60, it is not necessary to get that rough and you often end up maiming your surface, which needs a lot of work to make it right again. I mostly use 80 or 60 and that's enough to remove most coats. Only when it's a real mess I take out Saphir 50, but I wouldn't dream of using 24 or 36 grit. Might as well use an axe.

 

[mouppe]

+1 on the low grits. I use cristal 60 to get rid of bandsaw marks but that's about all.

 

[MrDanBrown]

Solid surface is where I spend the time on my rotex 125, and all I say if it's a black colour don't skip grits at all and Plowright right through from 80 on your seams and cuts all the way up to the desired finish I look to finish around 400's then polish as most of my work is kitchen and bathrooms and a higher finish just shows up more of the marks made day to day and makes the surfaces easier to maintain, tips I've got would be never start the sander then take it to your work, start the sander whilst placed on the work this helps reduce heavy marks caused by a fast spinning sander not flat to the work, and the more random your actions the less likely you'll get swirls formed by sanding in a repetative pattern, and nothing beats a good belt sander to get things flat before getting out my rotex to add that world class finish. Oh and as much as it's a pain in the butt allow decent time to add that quality finish I usually spend 3-4 hours sanding an average size kitchen and when I've done bigger work in kfcs, mc donalds, casinos etc I've been at it for days! Haha

 

[FEStastic]

Hi
a lot of the manufacturers say not to use a belt sander.
Have you found any problems with it, or are you careful

Thanks FEstastic

 

[Mavrik]

I have a belt sander and find it invaluable for the "right" jobs.
Inverted it works wonderfully in a a jointer type of way for thin strips of wood.
I make marimba's - so find the rounded end is ideal for helping to shape the curve underneath the keys.

But it's a dangerous beast to use to try and level a flat table.
I'm sure skill would help; but very easy to create grooves.

I have been tempted to acquire the "cage" that the belt sander sits in - which apparently controls the contact and height very precisely