Sanding 101 (Mirka Deros)

[CarlsonCarpentry]

Ill start this by saying I am a carpenter by trade... not an experienced woodworker.
This last year my craigslist browsing hobby paid off and I ended up with a Mirka Deros for dirt cheap. This was kind of my first introduction into high end tools. I had never even heard of that company or systainers or anything. Anyway...

I've been using this sander for about a year and I love it. Low vibration, low noise etc. But lately I have been noticing it is "squirrly" and jumping around on my projects. That is when I remembered I had turned down the RPM's (I believe I had read on here that NO ONE should be sanding with max RPMs). Turning them back up solved my problems.

But that is when I started thinking. I am using the "cadillac" of sanders (I had only used a Dewalt ROS previous to this) and I don't know much about sanding techniques or why my sander even has RPM settings.. So I am wondering where do I do some reading or youtubing about how to maximize the potential of my sander and gain the knowledge that will let me get the most out of it?

Hope this kind of makes sense, thanks for any help.

 

[ryanjg117]

Congrats on the find. I've only seen a few Mirkas on my city's Craigslist and they tend to be priced very high.

The "squirreliness" you refer to could be caused by a few different things, sanding speed certainly being one of them. Another factor is the amount of vacuum suction you're using. If you happen to have a vac (like a Festool) with variable suction, I find turning down suction speed can improve control.

A good resource for learning more about RO sanders is the Festool ETS supplemental manual:https://www.festoolusa.com/-/media/...ownloads/manuals/ets_sanders-supplemental.pdf

Even though it is oriented to Festool products, there's a lot of good wisdom there that applies to any quality RO sander.

Just a couple of other notes that I've found helpful:

* Don't put a lot of force down on the sander when it's operating; let the paper do the work. This will cut down on micro-swirls. It can be tempting to try to get extended life out of your paper, and I've certainly been guilty of this, but if I'm working on a piece that will be stained, I'll be extra careful on applying light pressure.

* Keep your grit jumps to a minimum, within reason. If you try jumping from 80 grit to 320, you'll absolutely have swirl marks. You need to step up with intermediate grits. While it's a bit tedious to keep applying paper, at the end of the day you're saving time. Each grit only needs 1-2 passes, quick work.

 

[simonh]

I had the Dewalt ROS and switched to a Mirka DEROS. The motor certainly seems to have more torque at lower speeds and applying much pressure it can soon be grabby in my experience. At higher speeds this doesn't seem to be an issue.

I normally run around 7-8000 rpm, let the paper do the work, maybe start with a lower grit so I don't need to put pressure on the sander, then work through the grits fairly quickly once first grit has done the major flattening.

 

[CarlsonCarpentry]

Congrats on the find. I've only seen a few Mirkas on my city's Craigslist and they tend to be priced very high.

The "squirreliness" you refer to could be caused by a few different things, sanding speed certainly being one of them. Another factor is the amount of vacuum suction you're using. If you happen to have a vac (like a Festool) with variable suction, I find turning down suction speed can improve control.

A good resource for learning more about RO sanders is the Festool ETS supplemental manual:https://www.festoolusa.com/-/media/...ownloads/manuals/ets_sanders-supplemental.pdf

Even though it is oriented to Festool products, there's a lot of good wisdom there that applies to any quality RO sander.

Just a couple of other notes that I've found helpful:

* Don't put a lot of force down on the sander when it's operating; let the paper do the work. This will cut down on micro-swirls. It can be tempting to try to get extended life out of your paper, and I've certainly been guilty of this, but if I'm working on a piece that will be stained, I'll be extra careful on applying light pressure.

* Keep your grit jumps to a minimum, within reason. If you try jumping from 80 grit to 320, you'll absolutely have swirl marks. You need to step up with intermediate grits. While it's a bit tedious to keep applying paper, at the end of the day you're saving time. Each grit only needs 1-2 passes, quick work.

Thanks a whole lot! That is great info. I am guilty of a couple of those things. Probably combined have been my problem. I do have a variable suction vac (Mirka vac) that I tend to leave cranked up. I guess I don’t need that much suction to capture light sanding dust. I also tend to push a lot because I am impatient and not let the sander worker.
I will explore that link you shared and see what else I can learn.

 

[CarlsonCarpentry]

I had the Dewalt ROS and switched to a Mirka DEROS. The motor certainly seems to have more torque at lower speeds and applying much pressure it can soon be grabby in my experience. At higher speeds this doesn't seem to be an issue.

I normally run around 7-8000 rpm, let the paper do the work, maybe start with a lower grit so I don't need to put pressure on the sander, then work through the grits fairly quickly once first grit has done the major flattening.

Yes I am experimenting now and finding that low speed plus too much pressure it does grab a lot. By backing off pressure and upping speed it has been much smoother. Thank you!

 

[aloysius]

Congratulations on your purchase.  I'm extremely impressed with Mirka's range too.  In fact, Mirka alternatives have made almost all my other sanders redundant now.  I have a couple of DEROS in 8 & 5 mm orbits, and a small DEOS, plus a delta-head Delmeq (a Dutch badge-engineered Mirka).  Not just effective and efficient, these Mirkas (& their Delmeq, Indasa, Sumaki & Carsystem clones) are extremely lightweight and easily handled, with excellent ergonomics.

The only downside is the need to continuously hold down the on/off/speed variance paddle.  At times, for extended sanding sessions, I've resorted to temporaily taping down the paddle with electrical tape so that I can more easily vary my grip in awkward situations, such as vertical & overhead tasks.  The light weight & (relative) lack of vibes in comparison to the cruder alternatives allow me to continuously sand much longer between spells than with their predecessors.  I'm personally not a huge fan of interchangeable power cables either.  Just as with the Fuss-Tool's Plug-It (bodge-it??) cables, Mirka's may at times provide imprecise connection or display premature wear of the electrical interconnecting terminals.  I'd advise you purchase a spare, just in case.  Mirka's clones have my preferred fixed power cables.

I've sold off both my Festool Duplex linear/moulding sanders, plus my Deltex & RS100 CQ orbitals & Rotex 150 & 90 random orbitals.  The only Festool 'keeper' has been my BS105E big belt sander, which (being a Holz-Her design, with their marvellously effective sanding frame) is better than any other I've ever used.  But the others were just too big, too heavy, too crude and often ineffective for my particular sanding tasks.

I've also retained my Bosch mini-delta GDA 280E & a couple of SXE 400 Metabos as both are infinitely more versatile & useful in inaccessible situations, convex & concave curves than Festool's ineffective RO90DX.  The bigger platens on Mirka's range (or any other's for that matter) prevents fine detail work.  The larger orbits on their orbitals means they're just faster & more effective than the old-fashioned Festools tend to be.

Using 'pad saver' discs & rectangles on your platens will greatly extend the life of velcro covered pads, particularly when using mesh abrasives.  The more ubiquitous availability of said mesh from the likes of Mirka, Sia, Festool, DeWalt (& probably others too) makes for a whole variety of types , qualities & price points for these remarkably effective abrasives.  I find best results with my vac's suction turned down to about 12 o'clock/50% or less.  The dust extraction capabilities of mesh abrasives seems to require quite a bit less suction power than paper-based abrasives.