ROS finish problem

[Shedhand]

Hi all. Got a problem which i've had for ages but im ghetting fussy now and want to solve it. A couple years ago I had Festool ETS 150/3 ROS. When sanding the eventual xposed face of, say a table top, I noticed that from 40 grit up to about 120 the sander left little circles all over the surface. If I started at 40 grit on a sawn surface as the saw marks disappeared the sanding discs left their little circles behind and as i moved up the grits they got fainter but were still noticable in the right light. In the past I have just kept going up to my standard 2-3000 grit foams attaining a glass like finish. Howver when putting on wax or wipe on poly or even shellac the little circles become more visible. Now I recall some telling me to wipe the surface over with a tack cloth between grits which i always do but the little circles are still there. Time goes by, sold my tools when in need and now starting to get some good kit back together. I recently bought a Metabo ROS 150 GTHO or something (329 bucks so its reasonable quality) and I've been using it to sand a table top made from a very dense and colourful hardwood (its Eucalypt from Vic but don't know what brand - very purty tho :wink: ) my clamping is very primative as I also sold all my loverly Bessey Ks. I have 2x1500 and 2x1200 bessey pipe clamps so there was a fair bit of sanding to do to get the able top flat after gluing up. Started with the big ancient Elu belt sanding monster with 40 grit belt to rip the mountains off and got it reasonably flat using a steel straight edge and chalk marks to achieve reasonable flatness. Then got the Metabo to work. Started at 40 grit. Ughhh! barely made a mark on the deep scratches left behing by the Elu. Anyway I persevered in 20 minute bursts to give my stuffed shoulders some rest. The Elu marks are still evident but faint except now I have the problem of the little circles from the ROS with 40 grit disc. I kept at it and went through 60, 80, 100 and 120. Can't get rid of the circles. every grade up to 120 leaves them behind. Tack cloth and damp cloth between grits. What the hell am I doing wrong. Wipe on poly is damned expensive for a pensioner and nothing makes me more p#ssed off than putting the poly on the finished surface only the have these bloody little circles standing out like dogs nads. By the way, I've tried a million brands of disc (not quite but you get my drift) and the same with all of them. I'm connected to a dusty and I've tried various speeds for each grit. Nada! Any clues anyone. :?
Cheers
Sheddie back in the shed

[Kuffy]

I use a milwaukee ROS 150 E-2. its similar to your metabo, dual function random orbit at 3mm circles and 6mm circles. I use the 6mm orbit setting for roughing away the surface grits from 60#->180#, then ill set to the 3mm orbit setting for the finer grits for finishing. I usually finish with oils, and mostly I burnish them into the tops from 400# up to a finer grit until i'm happy with the sheen. The weight of the machine itself is enough, you dont need to add any extra weight via your arms/shoulders.

[DaveTTC]

Pedal powered lathe

EDIT Not sure what hapened here. this post was meant to go in a thread about a bike frame


Dave the turning cowboy

turning wood into art

[Ilya]

Hard to say really without pics, maybe you have too high standards. I have exactly the same Metabo by the sound of it. Just with each grit I sand until the circles of the previous grit are completely gone. There are, of course, new circles from the new grit, but they are fainter and fainter as you go higher with grits. Once I go to 1k grit, and then finish with oil, I cannot see any circles... What sequence of grits do you go through?

[Shedhand]

I use a milwaukee ROS 150 E-2. its similar to your metabo, dual function random orbit at 3mm circles and 6mm circles. I use the 6mm orbit setting for roughing away the surface grits from 60#->180#, then ill set to the 3mm orbit setting for the finer grits for finishing. I usually finish with oils, and mostly I burnish them into the tops from 400# up to a finer grit until i'm happy with the sheen. The weight of the machine itself is enough, you dont need to add any extra weight via your arms/shoulders.thanks mate, but i never use pressure. I have serious arthritis and rotator cuff problems in both shoulders and just holding the tools is painful so I do most things in small bites. On the surgery wait list for a series of big deal spinal surgeries which will solve some of my problems but not shoulders yet.
cheers

[mark david]

Yeah, tell me about it!

Have had the same problem, first off 40 grit is way to coarse on almost any timber, maybe ok if you need to get rid of loads of paint or varnish you are better of with a minimum of 60 but preferably 80 grit to start with even 120 grit is pretty coarse and leaves bad swirl marks.you need to be meticulous going down through the grit grades 120 180 240 320 and so on.Realistically no amount of sanding with super fine discs will get rid of the marks left by the coarser discs if you try to rush it.

Be sure to regularly examine the discs as clogged portions can leave really bad swirl marks.
If you are starting out with machined timber I would generally not go any coarser than 180 to start with.

I restore a lot of low end furniture and regularly need to resand surfaces and dont worry too much about getting the best finish, usually the swirl marks are invisible until you apply a stain or finish and they magically appear.

Interestingly I have handled a lot of commercially mass produced furniture that has these swirl marks in the timber ?
What
I think the best advise is don't start with a coarser grit than you need too you will just spend more time trying to get rid of those marks.

[Shedhand]

Hard to say really without pics, maybe you have too high standards. I have exactly the same Metabo by the sound of it. Just with each grit I sand until the circles of the previous grit are completely gone. There are, of course, new circles from the new grit, but they are fainter and fainter as you go higher with grits. Once I go to 1k grit, and then finish with oil, I cannot see any circles... What sequence of grits do you go through?
If rough sawn - 40/60/80/100
Else
120/150/180/240/320/400/500/600/800/1000/1200/1500/foams from 2k to 4k.
Then wax or wipe on poly.

I do have high standards and get properly rewarded for it :2tsup:
cheers.

[Arron]

The Elu marks are still evident but faint except now I have the problem of the little circles from the ROS with 40 grit disc. I kept at it and went through 60, 80, 100 and 120. Can't get rid of the circles. every grade up to 120 leaves them behind

Yep, thats what I find - every grit 120 and over on an ROS leaves little spirals behind. I'm sure you could get rid of them if you sanded deeper with every grit, but if you have stuffed shoulders (me too) then who wants to do that ?

Realising this limitation, I use drum or big boy sanders up to 180 or 240 grit, then just a quick once over with 240 and/or 320 grit on the ROS, usually followed by 400 (just cos I like it, it plays no useful role in the finishing process).

240 grit doesnt leave spirals.

I think thats how these tools were designed to be used. Think cabinetmaking workshop - think efficiency - drum and stroke sanders for most of the real work, an ROS for just the finishing off. Trying to finish from 40 grit down on an ROS is an abberation. Possible, sure, but inefficient, not what they are designed for and you should treat your body with more care.

Regards
Arron

Ps. Nice fish in your avatar. Bluefin ??

[Shedhand]

Yeah, tell me about it!

Have had the same problem, first off 40 grit is way to coarse on almost any timber, maybe ok if you need to get rid of loads of paint or varnish you are better of with a minimum of 60 but preferably 80 grit to start with even 120 grit is pretty coarse and leaves bad swirl marks.you need to be meticulous going down through the grit grades 120 180 240 320 (tel:120 180 240 320) and so on.Realistically no amount of sanding with super fine discs will get rid of the marks left by the coarser discs if you try to rush it.

Be sure to regularly examine the discs as clogged portions can leave really bad swirl marks.
If you are starting out with machined timber I would generally not go any coarser than 180 to start with.

I restore a lot of low end furniture and regularly need to resand surfaces and dont worry too much about getting the best finish, usually the swirl marks are invisible until you apply a stain or finish and they magically appear.

Interestingly I have handled a lot of commercially mass produced furniture that has these swirl marks in the timber ?
What
I think the best advise is don't start with a coarser grit than you need too you will just spend more time trying to get rid of those marks.
Thanks mate, I start low on rough sawn stock as I don't have a thicknesser or jointer. If I have dressed stuff I start around 180 (hardwood) or 240 (softwood). I keep the Ros pads clean and pick the nits of the back of the discs.

[Shedhand]

Yep, thats what I find - every grit 120 and over on an ROS leaves little spirals behind. I'm sure you could get rid of them if you sanded deeper with every grit, but if you have stuffed shoulders (me too) then who wants to do that ?

Realising this limitation, I use drum or big boy sanders up to 180 or 240 grit, then just a quick once over with 240 and/or 320 grit on the ROS, usually followed by 400 (just cos I like it, it plays no useful role in the finishing process).

240 grit doesnt leave spirals.

I think thats how these tools were designed to be used. Think cabinetmaking workshop - think efficiency - drum and stroke sanders for most of the real work, an ROS for just the finishing off. Trying to finish from 40 grit down on an ROS is an abberation. Possible, sure, but inefficient, not what they are designed for and you should treat your body with more care.

Regards
Arron
Yes, I dream nightly about a big fat drum sander after a day finishing :(.treat my body better? That's what my surgeon said as he was booking me in for some heavy duty spinal work.:no:
cheers mate.

[Arron]

Yes, I dream nightly about a big fat drum sander after a day finishing :(.treat my body better? That's what my surgeon said as he was booking me in for some heavy duty spinal work.:no:
cheers mate.

Yes, I did realise you are probably not in the market for a drum sander at present - I was really just pointing out how these tools are really designed to be used, and why results might be sub-optimal if used in any other way.

I guess you missed my question about your avatar.

Arron

[FenceFurniture]

Yairs, it gives me the irrits too. There is a "sweet speed" at which to move the sander back and forth, and it's something to do with the speed of the orbit and rotation. Moving very slowly seems to be reasonably ok, and quite fast movement is better still (I'm using an ETS 150/3). So, I do the hog work with the first chosen grit, and then at the end of the grit I make sure I cover the whole surface with fast strokes and quite a few of them with the grain, not across it. If you think about it, the little swirl has to be elongated with a much faster stroke, and therefore more like a straight line.

I think that the sander speed (the machine speed) also has something to do with it, but I'm buggered if I know how to work that out. Someone like BobL may be able to calculate what's going on.

The problem is that with the coarse grits the timber surface is still matte so they can be damned difficult to see. Shining a light at just a few degrees off the timber surface helps to show them up.



Today I was working with Huon, and after getting swirls in much harder Blackwood a couple of days ago I thought I'd better try something different as it could be horrendous on Huon. On the Blackwood I had to re-do a whole corner after finishing at 3000. Didn't see the rotten little blighters until I moved the board "just so" under the oblique light. :~

I started with 80 to get rid of the ridges from terrible jointing the timber seller had done. In retrospect I could have started at 120 because they just vaporised at 80 grit. :roll: I'm too used to nasty hardwoods I guess. After the 80 grit I spent much more time with the 100, 120 & 150 than I usually do (I don't seem to get swirls from 150 up).

SUCCESS! There were still a couple of very small ones, but I'm afraid the answer seems to be spending more time with the coarser grits and increased sander movement speed (and the grit upper limit will depend on your sander and sander speed).

HTH
Brett

[Shedhand]

Yep, thats what I find - every grit 120 and over on an ROS leaves little spirals behind. I'm sure you could get rid of them if you sanded deeper with every grit, but if you have stuffed shoulders (me too) then who wants to do that ?

Realising this limitation, I use drum or big boy sanders up to 180 or 240 grit, then just a quick once over with 240 and/or 320 grit on the ROS, usually followed by 400 (just cos I like it, it plays no useful role in the finishing process).

240 grit doesnt leave spirals.

I think thats how these tools were designed to be used. Think cabinetmaking workshop - think efficiency - drum and stroke sanders for most of the real work, an ROS for just the finishing off. Trying to finish from 40 grit down on an ROS is an abberation. Possible, sure, but inefficient, not what they are designed for and you should treat your body with more care.

Regards
Arron

Ps. Nice fish in your avatar. Bluefin ??sorry mate, missed the ps. From memory it was a foul day down around Tasman Island. I think we got 4 Yellowtail Tuna and 3 Bluefin. Kept one of each and put the big ones back. The yellowtail in the avatar was about 25kg from memory and we got a 40 kg bluey.
cheers.

[Ilya]

I still don't understand the source of the problem. I can think of two reasons why this happens:
1) you sand all the way through the grits properly, but the final grit leaves swirls that you still see. I don't think this is possible, since you sand up to very high grits.
2) Somewhere in the process of sanding, when switching to finer grit you do not fully sand the marks from the previous grit. What helps me is after 320 grit ROS session, I go with 320 grit hand sanding along the grain until all the marks from ROS are gone. Then I continue sanding with ROS, and repeat hand sanding with the finest grit I reach with ROS.

[FenceFurniture]

I still don't understand the source of the problem.Hi Ilya, it's swirl marks from the coarser grits only, and probably the starting grit. The matte finish at that stage restricts being able to see them until you've moved right up to the polishing grits, when they can stick out like nads, as Sheddie says. I think the most important thing to do is give the job a really thorough inspection in oblique light after each grit up to about 120. That's a bit tricky and time consuming to inspect so minutely when you're doing a table or similar, but if not then a price is paid....

[ian]

I think in part the "cause" of the problem is working with rough sawn timber through to final finishing.

I think that before gluing the boards to make a top you should sand -- if that is your only option -- through to at least 120 to remove the saw marks and get boards of uniform thickness
then as the project progresses, you should aim to sand at least one grit finer as you complete each step.

However, unless you have a drum sander -- sanding rough sawn timber through to a finish ready surface has to be one of the more difficult WW tasks.

Almost certainly, your swirl marks are the result of not completely removing all the swirls from the coarsest grit you started with

[q9]

40 grit is really grinding, not sanding. The problem is really the cross cut wipes of the abrading surface are going to cut and tear deeper than you want and it will take a long time with a higher grade to get rid of them. Sanding with the grain will be better (ie not ROS) as those deeper cuts will disappear into the grain, but really you need to machine finish after sawing, jointer or thicknesser...

So my advice is change tools, or change grits. I'd never use 40 as a start to anything I wanted to look at.

[Shedhand]

I still don't understand the source of the problem. I can think of two reasons why this happens:
1) you sand all the way through the grits properly, but the final grit leaves swirls that you still see. I don't think this is possible, since you sand up to very high grits.
2) Somewhere in the process of sanding, when switching to finer grit you do not fully sand the marks from the previous grit. What helps me is after 320 grit ROS session, I go with 320 grit hand sanding along the grain until all the marks from ROS are gone. Then I continue sanding with ROS, and repeat hand sanding with the finest grit I reach with ROS. G'day Ilya, yes I would love to be able to hand sand and hand plane for that matter but as I alluded to earlier, I have some very debilitating problems with my joints. Arthritis, Cervical bilateral ferominal stenosis, bi-lateral epicondylitis, carpal tunnel and a lumbar spine rapidly losing its discs. Everything is a pain for me but I decided to keep going until I can't. Hopefully the upcoming surgery will allow me to continue walk upright for a few years yet. :2tsup: And yes the "dark side" is much cheaper. Derek (Cohen)is my hero! :D

[mark david]

Hi absolutely, really coarse grits that a really going to a major problem, if you are using these to derss rough sawn timber, although have not come across this technique before but if you don't have a thicknesser or drum sander then you need some other method.Using bench and block planes will save you a lot of time and money in the long run.

I certainly don't recommend using anything coarser than 120 grit on any timber you want to give a sprayed or lacquered finish.
I am not a huge fan of using super fine grits either to be honest,if I am using jarrah or marri for instance I don't go any finer than 320 grit, I was even told by an experienced furniture maker that he didn even go beyond 240 grit on jarrah it is just a waste of time.

Pine is one of the worst timbers I have found for showing the swirl marks due to its softness and grain structure and have major problems with it after using coarse grits to remove old varnish



Hi Ilya, it's swirl marks from the coarser grits only, and probably the 1starting grit. The matte finish at that stage restricts being able to see them until you've moved right up to the polishing grits, when they can stick out like nads, as Sheddie says. I think the most important thing to do is give the job a really thorough inspection in oblique light after each grit up to about 120. That's a bit tricky and time consuming to inspect so minutely when you're doing a table or similar, but if not then a price is paid....

[FenceFurniture]

I was even told by an experienced furniture maker that he didn even go beyond 240 grit on jarrah it is just a waste of time.Jeez Mark, I'm not sure if I want to buy any of his furniture then.:; This is the result of going up to 3000 grit (and no finish applied), which I definitely wouldn't call a waste of time.

http://www.woodworkforums.com/attachment.php?attachmentid=324203&d=1409738461

Give the chosen finish the best start, I say. Perhaps he used 2 pack finishes, in which case he could get away with a much lower grit I suppose.

[mark david]

Yes I can imagine what kind of finish you you can get with a 3000 grit but basically you would be burnishing the surface, if you are not then going to apply any kind of surface finsish then then fair enough but its not like polishing a piece of metal, you still need a final finish to acheive any durability.

If you were going to spray or lacqeur the surface then you would probably not be able to tell whether it had been sanded to 300 or 3000 and is quite likely a very fine grit might even compromise the surface adhesion of any finish applied to it.

the last piece of furniture I made was sanded to about 240 grit and sprayed with Becker Acroma dm307 it still looks like wood and not a plasticky finish


Jeez Mark, I'm not sure if I want to buy any of his furniture then.:; This is the result of going up to 3000 grit (and no finish applied), which I definitely wouldn't call a waste of time.

http://www.woodworkforums.com/attachment.php?attachmentid=324203&d=1409738461

Give the chosen finish the best start, I say. Perhaps he used 2 pack finishes, in which case he could get away with a much lower grit I suppose.

[LGS]

Hi,

There is an oil finishing method which requires hard burnishing. At 4000g the finish is sensational, at 400 it's a waste of time. The finish is highly resilient and is unaffected by heat, moisture and spills of food and the like.

As for not using anything higher than 240-320 on Jarrah, good luck to your mate. I strongly disagree.

Regards,

Rob

[mark david]

Each to his own of course, although I suspect the burnishing oil requires the burnishing at the application stage of the oil and not before.

Oil finsishes are known to darken significantly with age and are not to everyones taste.


Hi,

There is an oil finishing method which requires hard burnishing. At 4000g the finish is sensational, at 400 it's a waste of time. The finish is highly resilient and is unaffected by heat, moisture and spills of food and the like.

As for not using anything higher than 240-320 on Jarrah, good luck to your mate. I strongly disagree.

Regards,

Rob

[Evanism]

I've read the thread from top to bottom and I'm at a bit of a loss. My Festool ROS125 is nice with the dust extraction, but I've found over sanding does nothing but waste time.

I've found I'm under the pump for time, so I turn off the random function for 80, 120 and sometimes 180. I lift the tail of the sander to only just alleviate the pressure on the back of the pad (let's call it a 5 degree lift) and rotary sand at full blast. Farting around with slow speed makes no sense.

As far as movement, I move the sander in a simple snakes-and-ladders fashion with a 50%-ish overlap. I'd say it's moved about 7 to 8 seconds per 30 cm.

I then turn to random function on on either 120 or 180 dependant on the wood and do up to 240. I might note that the random function isn't really random if any pressure is applied. The disk just vibrates, it's only when the whole disk also rotates anticlockwise that it takes on a more hyper-detailed Spirograph-like function....any pressure and it's just vibrating in small circles.... Could this be your problem?

The paper is used to death before its thrown out.... For I have the poverty!

The disks are occasionally cleaned using the $5 Big Erasers that are grabbed as extra throw-ins when buying from Machinery Warehouse or Rockler.

Surprising that FenceFurniture experiences this, I'd regard him as the Sanding King. Those tests he did were exhaustive and very detailed. After 900km of sanding he should be the grand master!

Maybe burnishing up a scraper and finish with that? I love the finish a freshly curled scraper gives.

Has anyone ever tried finishing with some 0000 steel wool under the sanding pad?

[Ilya]

That is tough - hopefully you will get a chance to get a drum sander, this reduces the time and effort with ROS immensely. Definitely what you need.


G'day Ilya, yes I would love to be able to hand sand and hand plane for that matter but as I alluded to earlier, I have some very debilitating problems with my joints. Arthritis, Cervical bilateral ferominal stenosis, bi-lateral epicondylitis, carpal tunnel and a lumbar spine rapidly losing its discs. Everything is a pain for me but I decided to keep going until I can't. Hopefully the upcoming surgery will allow me to continue walk upright for a few years yet. :2tsup: And yes the "dark side" is much cheaper. Derek (Cohen)is my hero! :D

[Ilya]

Shedhand, I would imagine that you are not doing a huge number of project - maybe there is a forum member or a woodies club near you that have the drum sander that they can let you use?

[FenceFurniture]

Shedhand, I would imagine that you are not doing a huge number of project - maybe there is a forum member or a woodies club near you that have the drum sander that they can let you use?Or at least a jointer.....

It is a pain in the butt to load up the car etc, but probably less than the aggravation from 40 grit. A six pack of something decent should do the trick.

[Shedhand]

Many thanks to LGS (Rob) for dragging his gear down to my shed and spending the time to show me what I was doing wrong. Very enlightening I have to say.:2tsup::wink:
Cheers
Sheddie

[ian]

for the enlightenment of us all

what were you doing wrong?

[Shedhand]

for the enlightenment of us all

what were you doing wrong?i simply wasn't spending enough time on each of the grits and sanding too slowly which caused the swirlies plus Rob demonstrated to me that starting at 80# or 100# with the Rotex was as coarse as needed even on a piece of rough sawn Blackwood.
cheers
sheddie.

[dunamis]

I get the circles with my Festool ROS usually by pushing too hard. I make sure I go nice and light before I finish each grit. Then I make sure the next grit removes the circles from the previous one if there are any. Worn paper won't remove circles. As you say 220 and up don't make circles so it's really only critical to avoid them on the lower grits. On well machined timber (no tearout) I start at 150.

[Toymaker Len]

You should be using the belt sander with the grain up to 180 or 240 and then switching to the ros at 240 and going up through the grits. As others have said coarse sanding with an ros is really for removing paint and carving. At the coarse grits 40 60 80 you will see isolated large protruding pieces of grit and if you press hard they will bite deep into the wood and leave a mark which is up to a millimetre below the working surface. That means you have to take off more than a millimetre to eliminate the scratch. And I must add that going past 360 is good for jewellery boxes and turning but for furniture its unnecessary. If the furniture is to be used it will get the odd bump and scratch over the years and a superfine finish can be very unforgiving.

[FenceFurniture]

Sheddie, I reckon that today I worked out a good way to trap these annoying little buggers much earlier in the sanding process. But first a little preamble so it gets perspective.

1. In the course of my sanding marathon of 14 kms on the 1 metre timber length (not 900 km as was suggested earlier - that's from here to Brisbane, and it was only to Mt Victoria :U) I learnt that Festool Granat 320 grit and above drops a fine white powder on the job when the discs are new. This happens for about the first ten or so strokes. The same thing happened with Klingspor 800 and 1500 PS 33. 320 is the coarsest Granat I have used, so don't know if it happens with coarser grits - this might be relevant later).

2. I have been making panels from Red Cedar which is of course extremely soft (using those Mountain Ash bar clamps you sold me - I like 'em). Because the cedar is so flexible at the 14mm thickness I used that the panels still had some curves to be sanded out, and so I started at 120 grit. This left plenty of swirls in the soft cedar because at that point I was only after getting the panels flattish and smooth without any ledges.

When it came to proper sanding of them I knew I was going to eventually find plenty of swirls but that they would not be seen until the timber started to get glossy at around 800 grit (they will show up a couple of grits earlier with hardwoods).

So, I decided to run over the previous 120 grit finish with 800 grit Klingspor so it would drop the white dust and reveal the swirls - worked a treat, and I was able to spend the required time with 150 grit to get rid of the swirls (if it was harder wood then I'd probably stay at 120 or whatever was required for a while). They were really easy to see and get out with the 150 grit because the swirls had all filled up with a white powder.

O'course the Granat discs will probably not have DE hole patterns to suit your sander, but in this case that's irrelevant because we want the dust left on the job for visibility. Perhaps even turning the extraction off might help when using the fine grit after the coarse.

A caveat - I have only done this with red cedar, starting at 120 grit which is a different ball game to hardwoods starting at 40 grit, so your mileage may vary.

This is certainly a technique that I will employ for suitable situations in future.



And I just had another thought - you could rub talcum powder over the surface to show them up after the coarse grits. Probably easier, quicker and cheaper than changing to a fine paper.