Random Orbitals No More for Me - Here's why (see pictures)

[Nick Sorenson]

I've been ok with the Dynabrade Silver Supreme DA for a while as an acceptable finish sander. After this I don't think I'll touch it to a painted surface again. Check out this comparison in sanding quality.

The Dynabrade had a Sia Air 1000 Grit Foam after the finish was leveled with the National detroit and wet/dry papers. The only swirls/pigtails are from the Sia Air 1000 Grit foam pad that was used in the last step. Following this would be buff/polishing but I wanted to compare before I did that. As you can see there's a huge difference in finish quality.

The right side was sanded with 1200 foam on the National Detroit 600 inline sander pictured. Quite a difference. Much more than I figured there'd be. To be fair, the DA had 1000 grit while the National Detroit had 1200. But also to be fair, there is not much difference in finish quality appearance between the 1000 and the 1500 I have used on the Dynabrade. It's hardly noticeable. It seems like the real difference is with the inline scratch vs the random orbital scratch.

Also for background information on the test, the Dynabrade is the finest orbit (finishing sander for paint) at 3/32".

No more orbitals touching paint sanding for me. Also interesting, the N.D. inline sucks about 1/3 the air of the DA based on the time the tool can run full throttle before the compressor kicks in.

[Chris Fournier]

Once I get to the place that you are in the pictures, I'm always sanding in a linear fashion with the grain. I have found that the difference between 1000, 1200, 1500 and 2000 is readily discernable as I can see in your photos. I am not a big fan of power finishers on lacquered instruments most likely because I am not that proficient at the technique but to my eye (and ego) I tell myself that I can see the difference. With the small numbers that I have built at one time, I have stuck to hand work once I have this many hours into an instrument - chicken? Well yes...

[Scott Holmes]

One other comment... If you are using a 1000 grit vs a 1200P you are not comparing grits that are even close to each other; the "P's" and much finer than the CAMI grits.

Now if the papers are both P or both CAMI and the same grit, I'd say your orbit/pressure was too aggressive. I too usually will do this type of work by hand; it can be done by machine but there is a very fine line between the right touch and a mess or worse yet a burn through.

[Nick Sorenson]

One other comment... If you are using a 1000 grit vs a 1200P you are not comparing grits that are even close to each other; the "P's" and much finer than the CAMI grits.

Now if the papers are both P or both CAMI and the same grit, I'd say your orbit/pressure was too aggressive. I too usually will do this type of work by hand; it can be done by machine but there is a very fine line between the right touch and a mess or worse yet a burn through.

Scott, you are right on the P and CAMI scales differences. I'd have to check but I think these are both P rated. I know for almost certain the Red Foam pad on the orbital is a P scale grit at P1000. I believe what we are seeing though is what is making the scratch (i.e. the pattern that the tool leaves). A better test would be using the same exact product on both machines. BUT, I'd bet GOOD money (at least 50 cents) if I were a betting man that the result would be exactly the same if not very close.

Random orbitals almost leave a fuzzy look to their scratch. I don't find it to be very appealing. I always hand sand wood as a final measure to get this fuzzy look out.

Forgot to mention it in my first reply but to add it in in the edit, but to answer your assumption on the orbitals orbit being too aggressive, this is the smallest orbit made for auto finish sanding (3/32"). The usual orbits are 3/8 (Aggressive), 3/16" (usual medium duty) and what I have which is 3/32" (fine orbit for finish sanding). Also, with the foam pad the right pressure is easy. It's hard to give too much pressure since the foam has give. But pressure wise, I let the weight of the tool supply the pressure.