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Random orbital sander - advice please


(Gavin) #1

Hello all,

As a keen DIY-er I happened across the TP site about six months ago and have been trawling its depths picking up tips about technique and kit and wishing I had known two years ago (when I started redecorating my house) what I know now. Thanks for everyone’s contributions.

I have started tackling what for me is quite a big job - sanding the walls in my hallway and stairs prior to repainting. They are badly orange-peeled after years of repainting by previous owners, including a thick eggshell topcoat.

Having given it a try on the basis of recommendations here I have been thoroughly converted to Abranet and have now modified a Mirka backing pad saver to fit the hole configuration on my random orbital sander - a Bosch GEX125-1 AE (photo attached).

I love the finish I am able to achieve in my hallway, but the vibration using my ROS on the walls is killing my hands in no time at all. I am therefore considering whether it would be worthwhile investing in a different ROS, and would be grateful for advice about alternatives that allow the user to work for extended periods without numbing their hands.

My philosophy, incidentally, is that by doing this sort of thing myself I save a lot of money that would otherwise go on professional fees and spend some of that saving on kit to make sure I do the best job possible. I would even consider stretching to a Mirka ROS, but it would need to be a lot more comfortable to use.

Any advice would be gratefully received.

Many thanks,

Gavin


(Russ Pike) #2

Hi Gavin,

Nice to hear your utilising and having success with some of the tips and tricks found here on the TP website.
In my opinion the new Mirka Deros (Direct Electric Random Orbital Sander) is an awesome piece of kit!

Have a look at this: http://primedecoration.co.uk/meet-the-mirkas

I use this machine and the Ceros for 2 to 3 hours a day, often longer some days and it is very comfortable to use. My mate Jase (the Ace) Walker up in Preston also loves his Mirka:

As do many of the TP Crew

You could also try the HD (Heavy Duty) Abrasives that Mirka do?

Hope this helps

Russ


(dave D9 decor) #3

I have the Festool Rotex 125 which I find superb for larger flat areas as you are describing. I can’t praise Festool kit highly enough in every way; functionality, efficiency, ergonomics and its integrated system base. ihowever i’ve never used the Bosch or Mirka so can’t help with comparison.
Where are you based? I am lucky to have Power Tool Plus shop in Bristol who only sell top end pro kit and can visit there to compare and try out like for like
The Festool Granat (Blue) abrasives are seriously good - the 40grit will rip layers of paint away in no time!
good luck!
dave d9 decor bristol


(Gavin) #4

Many thanks Russ and Dave - and Andy (by e-mail). I really appreciate your insights. I’ve attached a photo showing the texture of the walls I am tackling (there’s about 70m2 in total).

I took the plunge and went for a 125mm Ceros kit (from Rest Express). It’s lighter and has a lower level of vibration than the Deros, and I can live with the transformer, so couldn’t justify the extra expense (which would have included duplication of abrasives at 125 and 150mm). Rest Express contacted Mirka on my behalf and the latter sent me a generous sample selection of their other abrasives, including around 10 disks of 60 grit HD.

So far so very good indeed. I can easily manage 2-3 hours of pretty continuous sanding, comfort increasing (that is, vibration decreasing) with both speed and grit (I’m combining 80 and 120 disks). I’m using the Ceros with my domestic hoover, although not without the problem of bags quickly clogging, but at least they are cheap (and much easier to store than an extractor…).

The two challenges I face at the moment are dealing with some pretty uneven walls (low areas that are hard to sand, even with an interface pad) and paint clumping (pilling?) on the Abranet disks, especially in the centre where there is no extraction (which I suspect also means higher temperatures). Somewhere there is a perfect combination of grit, speed and pressure but I’ve not yet found it. So I’m probably getting through more disks than I need to. Toupret fine surface filler has been very helpful to deal with some of the more troublesome areas, and the thicker interface pad has allowed me to easily sand around a curved section.

I’ve had a go with a 60 grit HD disk today, and it’s probably 2-3 times more aggressive than the regular 80 grit in terms of how quickly it removes material - and very stiff and flat. One downside is that it sheds a lot more dust, another is that it’s easy to sand straight through to plaster where the surface undulates (and in some places patches of paint have ‘let go’).

Given time and patience it seems that even I (an amateur DIY-er) can achieve a lovely silky finish. I’ll report back once I’ve got some fresh paint on the walls, but my expectations at this stage are very high.

Thanks again for your advice,

Gavin


(dave D9 decor) #5

I may be way off the mark here - its hard to assess prep work unless you’re actually there - but consider skimming over large areas with Toupret Planeo G skim filler. (more on their website and you tube)
I recently had a job with three of the bathroom walls previously painted that had crazed or mudcracked all over. So a wipe down with meths to neutralise, then a coat of Planeo G and it got me a new plaster skim finish ready for priming and painting.

ignore all of the above if I’m giving the wrong advice for your project!
hope it goes well though
Dave d9 decor Bristol


(Andy Crichton) #6

Sounds good advice to me Dave. As you say unless you see the job, it is tricky to advise 100%. When working on a job you also pick up what is best as you go along. Some sanding, some filling, as long as you have the kit to hand, and keep thinking, you will get it right.


(Russ Pike) #7

Tbh, I would have opted for skimming that, another option would be to use the orange top joint cement made by Gyproc, we call it aims as its used for aims taping joints in plaster board ut works great on this type of surface.

Also just wanted to add that the new Deros has a modified base plate with a star shaped central extraction port to avoid paint clumping (pilling) as mentioned above.
Unfortunately though its only on the 150mm base:

http://primedecoration.co.uk/meet-the-mirkas

Cheers

Russ


(Gavin) #8

Hello all,

I thought I would report back.

I am very happy with the Ceros. It’s comfortable enough to use for four hours plus with minimal hand fatigue and the dust extraction (even with a domestic vac) is fantastic (with regular bag changes…). Especially noticeable on the odd occasion when I forgot to turn the vac on and wondered why it suddenly seemed to be snowing. I used a dust mask (anyway) and ear plugs, the latter particularly to block out noise from the vac.

The 60 Grit HD disks turned out to be a bit of a problem: very aggressive, but also poor extraction and they seem to generate a lot of heat = lots of pilling, which in turn resulted in swirls and more heating etc. Probably better for timber surfaces.

I ended up getting through a lot of 80 grit Abranet disks, having decided that it made more sense to keep the rate of surface removal up (using sharp abrasives) than trying to persist with dull disks. I found that interface pads that got pilled could be restored with a soak in cellulose thinner and a scrub with a toothbursh.

I followed up with 120 grit, and that seemed quite smooth enough.

I used Toupret fine surface filler for finer imperfections and found it very easy to use. Memories of Polyfilla horrors and obviously filled screw holes now in the dim and distant past.

The final pre-painting result on the walls was absolutely stunning - virtually a polished finish. Seemed a shame to have to paint, and definitely exposed the limitations of my wall painting abilities. I imagine that only a sprayed finish could really do justice.

I used the Mirka hand-held hand sander for architraves and the like, and for areas where a more gentle touch was required, including filled areas on the walls and pre final coat on skirtings. My impression was that the initially aggressive removal of the Abranet abrasives with the hand sander very quickly dulled, although the abrasives remained sharp when used without being attached to the hand sander (e.g. just using an interface pad for strongly curved surfaces). In other words, the abrasive qualities remained, but needed more (fingertip) pressure than was possible with the hand sanding block.

For the painting I used:

  • Wooster Alpha brushes: liked these (1 and 2") very much, especially the 1" on architraves. I also tried a 2" Corona Cody, which I found too heavy.

  • Wooster pro-Dooz roller sleeves - maybe not perfect enough given the virtually flawless substrate?

  • Mythic All-purpose primer: very easy to achieve a lovely flat finish, albeit very thin and not very opaque, and I ended up doing multiple coats.

  • Little Greene Absolute Matt (Shirting - same for all LG paints) for the ceiling - beautiful soft finish.

  • Little Greene Intelligent Matt for the walls, applied with 9" Wooster Pro-Dooz rollers: needed three coats for a fully opaque finish, and I found it very difficult to achieve a perfect finish (despite following all of the advice on this site and Jack Puhl). The fact it is a very tall hallway, which is lit from a very acute angle (fanlight over the front door or recessed ceiling lights), meant both that I couldn’t complete ceiling to floor rolls (too high for a short-handled roller; too narrow for a long handled roller) and then any imprefections are ruthlessly exposed by the side lighting. I took the advice about rolling right to the edges with a 4.5" pro-Dooz roller, with excellent results (effectively zero brush marks visible in cutting in).

  • Little Green Intelligent Eggshell for skirtings/ architraves. I used ‘XIM latex extender’, but probably not enough so still got brush marks, especially on the larger areas of skirting (although I’m no fan of a factory sprayed look). Maybe I’m missing something, but I can’t work out why I should pay top top whack for ‘premium’ paint and then have to add antifreeze (or whatever) to it, in order to achieve a good finish, and on reflection that probably held me back from adding enough XIM. I am surprised at the level of plasticky surface sheen of the finish, especially when viewed at a very acute angle (we have stairs up from our kitchen to hall, so you end up with hall skirtings at eye level).

  • 3m 2090 masking tape, which took some of my nice matt wall paint with it (Grr), leaving me with some remedial work. But no bleeding at all.

I’ve learnt a lot from TP and am grateful that you have been willing to share your knowledge. My decorating abilities have leapt forwards, definitely helped by having the right kit. Other than involving a lot of time and effort, my only real problem is that it makes the rest of the house look distinctly scruffy…


(Andy Crichton) #9

Thanks for the thorough feedback Gavin. For the most part you seem happy. And have got it about right.

Skimming and sanding may have been quicker, assuming you are a dab hand with skimming and can offset the material cost with time savings, but it may be a wash. Without seeing it, cant be too certain. Academic now :slight_smile:

The roller finish, you could lay on with the 3/8 pro dooz and would get a flatter layoff with a micro plush. It is a 2 man job that route, though, and it sounds like the hall was a bit tight for a tag team.

I learnt a few good tips off a plasterer and painter team in Derby, who were skimming with Toupret fillers. They worked out the grits to suit assorted paint types. So for instance, vinyl matt is quite big particles (in terms of microns) so you need a 180 final grit and then the paint will lay flat. Mythic is a flat paint and finer 320 grit will secure a flat finish. Not quite translatable on a redec like this, but it shows that the polished surface was not ideal porosity for the Intelligent matt.

You highlighted quite an important feature with dust extraction sanding - a vac that powers on simultaneously with the sander. All decs without a dedicated Festool or Mirka vac been there with the mini snow storm!

There are a couple of schools of thought with the extender / conditioner in premium acrylic paint. Adding it yourself does give you full control to suit the temperature and ambient conditions. If XIM were added in the factory, it would not be present when you got it. You have to keep topping it up, as it loses its effect over the day. The XIM fans will definitely say you didn’t add enough.

Eico acrylic trim paint is 100% acrylic, it is formulated a bit better for levelling straight out the tin, but not perfect.

LG Shirting is not covering at all well, whoever you are.

Fair play to you and hope this gives a few more pointers to future DIY projects. Frever touching up your scruffy bits now?


(Gavin) #10

Thanks Andy.

‘…assuming you are a dab hand with skimming’. Not so much.

The interaction between sanding grit and paint particle size is a new one for me - perhaps something you could explore in more detail on your site?

I couldn’t justify the outlay for an extractor for a DIY job, but can’t imagine why a pro wouldn’t consider it a no-brainer in terms of productivity. As it was, I got through about £12 of vac bags.

I recall seeing a slightly negative remark elsewhere on TP about LG shirting. Are you referring specifically to the Intelligent Eggshell? When you say ‘not covering well’, do you mean that it’s hard to brush out, or not very opaque - or something else?

One final question, if I may: do you have a favourite laying off brush for water-based eggshell? I recall seeing a video of one of your TP colleagues painting kitchen cabinets with a wide and thin orange-bristled brush (I’m guessing a Picasso) that had been wetted, but haven’t seen anything like it on sale (perhaps looking in the wrong places). Despite regular washing, I found the 2" Wooster Alpha still tended to clump a bit - but on reflection perhaps that’s because I held back on the XIM.

Thanks again and all the best,

Gavin


(Andy Crichton) #11

[quote]Quote from Gavin on October 17, 2013, 18:32

The interaction between sanding grit and paint particle size is a new one for me - perhaps something you could explore in more detail on your site? [/quote]

You should be the Mirka poster child, spot on reasons to be kitted out properly

Poor coverage in all finishes

Royal and Langnickel


(Andy Crichton) #12

Been notified that the Mirka DEROS 110 volt is the first of the new Mirka sander line at MyPaintBrush. Good price on pre-order, looking at comparable it is on the money and comes with an extra systainer too. http://www.mypaintbrush.co.uk/accessories/mirka-online