Air powered orbital sanders?

[Kelby Van Patten]

My cost is way different than Martin’s.

I use a single phase 5 HP Quincy compressor. Full load is 28 amps at 240 volts. That’s a 5.6 kW load.
I live in California, where electricity is as expensive as anywhere in the country. I pay 32 cents per kWh. So, running full blast, I pay $1.80/hour to run my compressor for my Dynabrade.

I also have a Festool ETS 125. It has a 1.6 amp motor at 120 volts. That’s a .16 kW load. At 32 cents per kWh, that’s 5 cents per hour.

So, it costs $1.75/hour more for electricity to run the Dynabrade than the Festool. (It will be a MUCH smaller difference for those living in other states where power is cheaper.) On the other hand, the Festool will not last as long as a Dynabrade. The value of that depends on how long they each last, but that means that the cost difference of using the Dynabrade is less than $1.75/hour.

The Festool is a great sander, and I typically use it just because I already have my Festool vacuum near my bench, so it’s easy just to plug the sander in and go. But if I have a long sanding session, the Dynabrade is more comfortable to use. The extra buck an hour or so is not a huge factor for me.

Martin, how did you calculate a cost of $.15/min? That seems high to me, even for a 53 CFM compressor.

[Van Huskey]

The Festool is a great sander, and I typically use it just because I already have my Festool vacuum near my bench, so it’s easy just to plug the sander in and go. But if I have a long sanding session, the Dynabrade is more comfortable to use.

Try out a Festool ETS EC 125/150 or a Mirka Deros, they might well change your mind about comfort.

I completely get the hold air sanders have on people, a few short years ago this wasn't even a discussion. The "old" brushed sanders were less powerful, didn't last as long, had relatively high vibration and were very bulky. Then the PC 390(?) came along, ahead of its time, and ushered in a new age, despite dying an ignominious death as few saw its potential and it was only a fair representation of what they could be. Then the Mirka Ceros came out and boom traction started to be found, it helped Mirka had a significant commercial/industrial presence especially in Europe. Now Festool and 3M have adopted brushless sanders. For the commercial and industrial settings, they offer a lot of promise especially when it is time to replace or put in major portions of infrastructure like large compressors. While I may sound like I am proselytizing I don't mean it to come across that way just trying to point out it is a legitimate cost calculation to be made for business and for hobbyists brushless sanders allow them to have upper end quality in a ROS without the need to have a large compressor and the associated infrastructure and maintenance. For many it is hard to believe an electric ROS can be as good as a pneumatic one, I know it was for me until I owned one.

[Mark Bolton]

The 5 hp 3 phase compressor would heat up, because it only would put out 17 cfm, and any other use in the shop would be more than the compressor could handle. The maintenance of a compressor to run a sander was not worth it.

+1 This is the answer without a doubt.

The economics are in no way shape or form murky. They are clear as crystal. When you pick up an air sander you have in your hand a 250$ sander, attached to many dollars of air lines, which should be attached to a high quality filter (more$$), which should be attached to a refrigerated dryer (more$$) which is then attached to a FIVE HORSEPOWER compressor that, unless its a top brand, is going to struggle to keep up. The maintenance and expense of all of that, regardless of the ancillary uses for a compressor in a wood shop, make air sanders a loser. Hence it being mentioned in this thread and every other dynabrade thread that in the commercial world air sanders are going bye bye because large shops quantify the true cost of manufacturing a CFM of clean dry air.

I mean litterally? You need a 5HP Baldor motor to run a tiny little hand sander?

The worst part for us in the new DC brushless world was the discontinuation of the Ceros. That envelope is nearly exactly that of a dynabrade and has dust collection. Its small, compact, light, super smooth. I can see wanting to have a Dynabrade around for tight spots if you are running the Deros like Martin. I have looked at the surfprep and 3M electric options but cant get my hands physically on either to try though surfprep has a dealer in and area we travel to and if I can try one I will go that route when we add more sanders.

Large commercial shops running dynabrades has simpy been because there has been no viable electric alternative. They all knew, and still know, that those sander are profit hogs. The instant the Ceros and now Deros envelopes hit the market the math is crystal clear and they are moving.

[Mark Bolton]

Martin, how did you calculate a cost of $.15/min? That seems high to me, even for a 53 CFM compressor.

Your cost for running the compressor per minute is far more than just the cost of the electricity it consumes. Its the initial cost of the compressor, life span, maintenance program, repair, replacement, and so on. Your math on the electricity alone is a good reason to put the dynabrade in the drawer and only run it in applications where its the only option. By your math alone the electricity costs for the dynabrade are 36 times the cost of an electric not counting investment, maintenance, and replacement. There is simply not a chance in the world the dynabrade performs 36X better than even a mediocre electric sander.

[Kelby Van Patten]

Thanks, Van. I had a Mirka Ceros before they were discontinued. It died the first weekend I owned it. It was nice, but not superior to the Dynabrade, so I returned it for a refund.

[Kelby Van Patten]

Your cost for running the compressor per minute is far more than just the cost of the electricity it consumes. Its the initial cost of the compressor, life span, maintenance program, repair, replacement, and so on. Your math on the electricity alone is a good reason to put the dynabrade in the drawer and only run it in applications where its the only option. By your math alone the electricity costs for the dynabrade are 36 times the cost of an electric not counting investment, maintenance, and replacement. There is simply not a chance in the world the dynabrade performs 36X better than even a mediocre electric sander.

Mark, as far as including the other costs associated with the compressor, that depends on whether you already own and maintain a compressor for other purposes, which I do. Since I own and maintain it for other purposes anyway, the incremental cost associated with sanding is the electricity.

As for making decisions based solely on cost, all of the ROSs we are discussing -- including the Festools and the Mirkas -- are unnecessary luxuries given that you can buy a DeWalt for $70. But like many tools in our shops, cost isn't the only factor. If you like using the tool and it works for you, and if you choose to spend a little extra to have something you enjoy, then that's fine. My only point is that when you're dipping your toes into the higher end ROSs, if you already own a compressor, the actual dollars that it costs to use the Festool/Mirka and the Dynabrade is really not that much in the scheme of things. In fact, given that the Dynabrade is $180 and the brushless Festool is $400 ($220 more), even assuming my $1.75/hour delta (which is only true in CA), one would have to use the sander for 175 hours before the cost of electricity makes up for the price difference. For most of the people on this forum, that's probably years of woodworking before they even reach the breakeven point, let alone start saving money through the Festool. The dollars might be more significant if you are paying three guys to sand full time. But for hobbyists that are spending more than we need to anyway, if you already own and maintain a large compressor, the electricity is not as big of an issue as some here are suggesting.

[Martin Wasner]

Martin, how did you calculate a cost of $.15/min? That seems high to me, even for a 53 CFM compressor.

Methinks my brain locked up, or autocorrect hosed me and I didn't catch it. I bet I know what I was thinking. A 5hp motor costs me about $.01 per minute. I probably brain farted and went 1hp costs me $.01 to run.


15hp compressor is 11.2kw
I'm paying I think almost .16 per kw/hr.
That should be about $1.80 per hour? or $.03 per minute



A while ago I figured a 20hp motor cost me $2.40/hr to operate, or $.04 per minute.

[Mark Bolton]

Kelby, This will not read the way it should but the simpe fact of the matter is whether you own and maintain the compressor on not has no bearing on the math. The maintenance will go up with additional load, the life of the compressor will be reduced by additonal load. That IS an expense. Generating molecules of compressed air is directly accountable. Its not like you arbitrarily produce 30,000CFM of compressed air monthly and if you dont use the 30,000 they go into some AT&T roll over account to be used "for free" later. Any molecule of compresse air you dont have to manufacture is a direct gain for your business (or your families bank acCount).

This is a trap every single individual falls into when this dynabrade conversation come up (search the archives). Someone working in a large plant or factory shop will say "well we make tons of air anyway so we like our dynabrades". I can guarantee you that is not what the accounting department is saying. Quantifying your cost to make air to feed that sander is directly accountable. You made the first step in that accounting by stating quite clearly that your paying 36X in electric costs alone (forget the rest) to run an air sander as compared to an electric (and not a great electric to boot). So only you in your operation can quantify whether paying 36X (without all the other expenses included) to run that sander either equates to optimized output, better faster sanding, or maybe your just willing to pay 36X because it floats your boat to get to run air tools and its something youve dreamed of your whole life. I have no idea... but at the most rudimentary investigation into the cost of operation youve sumized that its 36X more expensive. A very short excel sheet would frank the differences in operating and performance between buying a DC brushless sander every few years and 36X the cost of operation plus additional compressor replacement and maintenance.

I dont need to do that math because I know for a fact I would never strap a 5HP motor to my backpack with a recip or rotary compressor attached to run a sander that fits in the palm of my hand. It only makes sense when there is no alternative option (the days of old when hand electric sanders were huge, slow, and inefficient). Those times are changing which again is why industry on mass is moving away from manufacturing very expensive molecules of compressed air.

Again you state that "if you already own the compressor the cost of operating is not that high". Your direct operating cost is 36X more, your compressor has a life span, you apply more load, the life span is shorter. Thats an additional cost. This is the math the accounting department is doing.

Your statements about things only being true in CA doesnt really make sense either because while energy costs may be less elsewhere they both go down proportionately. So the 1.75 an hour goes down to whatever the rate is in the boondocks of Louisiana, as does the operating cost of the electric. The lower energy cost will be directly proportionate. As more than likely will be the cost of living, the amount you can charge for work, what you will pay for gasoline, hard wood, soft wood, whatever. The loss of income to power the costly tool will be directly proportionate. Its why Europe is as a rule more "advanced" than us. Its not because they are simply smarter.. its because they pay the actual cost of energy and that actual cost is extremely painful, much more painful than we in the US have ever felt, so they optimize to reduce the pain. Try driving to Canada and filling up a 4 door 4 wheel drive dually diesel daily driver that doesnt have a single scratch in the bed because its a glorified car because the individual just "likes" driving it. Its the same thing. If your wealthy enough... have at it. If your into throwing dollar bills in the fire have at it.

These discussions always try to get blurred by the comments of "for most of the people on this forum" which is understandable. A hobbyist who really just gets a rise out of sanding with an air sander that they always dreamed of as a kid, or rotating their tires with an impact wrench because they always wanted one, has no bearing with regards to the economics of the tool. They run it because they want to regardless of cost. But it has no bearing on the math whether you sand for an hour a week or 120 hours a week. The cost of operation is grossly more and the performance does not match that cost other than in very specific circumstances which, yet again, is why industry on-mass is moving away from producing any molecules of compressed air they dont need to.

[johnny means]

And those are brushed, the life expectancy of a brushless sander is much longer.

Obviously, if they are being run in production 8 hours a day no electric will last 15 years one just has to work out the real cost of using air vs electrical, for the hobbyist like me energy costs aren't a big factor and it may give me a good excuse to buy a big compressor but I still prefer brushless electric.

Any shop running an orbital 8 hours a day is doing something really wrong

[johnny means]

Mark, as far as including the other costs associated with the compressor, that depends on whether you already own and maintain a compressor for other purposes, which I do. Since I own and maintain it for other purposes anyway, the incremental cost associated with sanding is the electricity.

As for making decisions based solely on cost, all of the ROSs we are discussing -- including the Festools and the Mirkas -- are unnecessary luxuries given that you can buy a DeWalt for $70.

Not once you understand the science of sanding and the economics of ergonomics.

[Van Huskey]

Any shop running an orbital 8 hours a day is doing something really wrong

A shop running enough doors to have someone doing nothing but finish sanding all day er day is doing something really RIGHT. 'Member production door plants use orbitals for finish sanding too...

[Alex Zeller]

To be fair a larger shop is unlikely to have a piston air compressor. We use rotary compressors which run for years only stopping for routine service. I think they are expected to last 30 to 40 years of continuous use.

[John Sincerbeaux]

I just finished upgrading my air system. Quincy 80 gal 5hp, refrigerated air dryer, Rapidair Max line pipes, Rapidair filter regulators. To date, my biggest air needs were my widebelt sander and spray equipment. I have two Ceros sanders I am happy with. I am in the market for a 3” air rotary buffer.... Really, the only options are air powered buffers/polishers. There are some electric ones but they look huge and impractical.

I seriously doubt Air sanders will ever be replaced in the commercial and industrial sectors. Take a look at the Dynabrade website. There are many many tools for many applications.

[Peter Kelly]

Any shop running an orbital 8 hours a day is doing something really wrong

Any busy solid surface shop will have a few going all day.

Not a real pleasant environment.

[Mark Bolton]

To be fair a larger shop is unlikely to have a piston air compressor. We use rotary compressors which run for years only stopping for routine service. I think they are expected to last 30 to 40 years of continuous use.

And the price per hour when you factor in purchase, maintenance, operating expense, is directly attributable to each and every cfm manufactured. Like Martin, I will guarantee you any large shop will be able to tell you specifically what their cost of manufacturing air is and even with a rotary it's far from cheap or free. Hence large facilities aggressively dealing with leaks and loss because those are buckets of profit flowing directly into the fire.

Our compressor is 50,000 hours. Even having a higher end unit when I need an impact wrench I run an electric unless I need the muscle of the pneumatic. Every drop of air I dont have to make, I dont have to pay to make.