Rick Christopherson said:
The reason why pad breaks were developed for electric sanders is for this very reason. Due to the mass of the motor rotor, the sanders do start up fairly slow and can leave erratic marks on the wood. Once the sander is in contact with the wood, the pad break is actually a detriment to finish quality. So if starting them up on the workpiece was a good thing to do, then pad breaks wouldn't be necessary.
For somebody who has the reputation of being an authority on Festool, it is a shame to see how misinformed you are on this subject.
Sanding pad brakes were absolutely NOT developed for that very reason you mention, and they certainly aren't detrimental to finish quality either.
Of course you nor anybody else here is going to take my word for it, going against the know and respected authority here, so I'll just take the liberty of quoting a
US patent site.
In its preferred embodiment, the preferred brake system disclosed in the present application prevents rotation of pad 22 when the motor is running and the pad is unconstrained by a workpiece surface but permits the random orbit sanding motion when the pad comes in contact with the workpiece surface. The objective of a brake for use in connection with random orbit sanders is to prevent the spin up of the pad to essentially motor speed when the pad is unconstrained by a workpiece. If the pad is allowed to reach motor speed such as in a free-spinning configuration, a user may gouge or scratch the workpiece when placing the spinning pad down on the workpiece. On the other hand, if the sanding pad can be constrained from spin up prior to the time that it is placed on the workpiece, this undesirable gouging or scratching or the like can be eliminated. Furthermore, such a brake eliminates the necessity for inexperienced users to remember to place the sanding pad onto the workpiece before starting the motor in order to avoid this problem, such as in prior art sanders without a brake. In addition, the present braking system eliminates the potential for a sanding disc or the like to be flung dangerously off of a free-spinning pad, eliminates the danger of personal injury from a free-spinning pad.
I don't need to remember people here how strict and precise patent applications have to be worded in order to have any chance at being accepted.
Rick Christopherson said:
You won't find pad breaks on pneumatic sanders because their rotors are lighter and they spin up to full rpm very rapidly.
The reason they don't have brakes is not the spinning up factor, but in the spinning down factor. You do are right about the fact that the weight of the rotor is important in this matter.
The differences between a pneumatic sander and an electric are basically twofold:
1) the electric sander has a big and heavy rotor as compared to the pneumatic sander,
2) the electric sander has a stationary switch that switches between the on and off positions and STAYS there when you don't touch it, while the pneumatic sander has a switch that opens when you press it and closes when you release it. As a consequence, you constantly have to hold the pneumatic switch for the machine to work while you can let go of the electric switch.
So now we can take a look at how people actually work in general with their sanders, and look at how those 2 differences mentioned above work out in practice. You see, people have the constant habit of taking the sander off their work to see what they're doing and checking the result. Now, with a pneumatic sander, you let go of the switch and due to the low weight of the rotor, the pad stops spinning almost immediately, no more than 1 to 3 seconds. With the electric sander on the other hand, spinning down can take A LOT longer, 15 to 20 seconds. AND you have to reach for the switch again to turn it off. As a result, when people work with electric sanders, they tend to let the machine running while they take it off the workpiece, while as with the pneumatic sander, they let it stop. Just waiting 20 seconds for a machine to spin down is too much time lost, while waiting just 3 seconds with the pneumatic is acceptable.
Now, as I mentioned in my first post, and as is mentioned in the patent application, once the pad is off the workpiece, the pad will spin up to a high speed, which is so high because the friction with the workpiece is gone. The motor is designed to have a workable power when the pad is on the workpiece, so when that friction is gone, all that power is put into the free spinning disc which as a result spins up to an undesirably high speed, basically turning it from a sander into a grinder.
To prevent this from happening, one bright mind eventually came up with the idea to install the pad brake, which is nothing more than a thin ring around the pad, adding extra friction to prevent the pad from spinning up.
Rick Christopherson said:
Once the sander is in contact with the wood, the pad break is actually a detriment to finish quality.
No, sorry, but once the sander is on the wood the pad break
completely loses it's functionality. And it is certainly not detrimental to the finish quality either, as the pad brake isn't that old of an invention and people, including me, still got very fine results working with machines that had no pad brake at all in the pre-pad brake era.
Btw, I am used to working with both pneumatic and electric sanders since I was 8 years old, we had plenty in the family body shop. That means almost 30 years now for me.
