Rupes 15 or 21

[mbkite]

What do you think would finish polish better.
Having read all of the Kevin brown method on larger orbits
I think the 21 is the ticket

But what do you think or know if you have used the rupes
Thanks all..

[Hazcat]

There are a multitude of things that affect the outcome and choosing between Rupes 15 or 21 is so far down on the list I wouldn't even consider it. Used correctly they should give the same finish.

[SR99]

Hi mbkite,
If you think about it, your question amounts to asking whether a smaller orbit (throw) gives a better final finish than a larger throw. The idea that a smaller throw finishes better has some "intuitive appeal" if you believe that finer/smaller motion equates to finer finished results.

The conventional wisdom from random orbital sander marketing (for wood finishing, which preceded the use of random orbital machines for detailing) has been that a smaller throw finishes better. Manufacturers sell smaller throw machines as "finishing sanders." However, that could have just been a marketing ploy dating back decades (capitalizing on the intuitive appeal) to get people to buy additional special-purpose machines. After all, manually using a sanding block (where your "throw" is a huge 6 inches or so) and the right abrasives can produce immaculate finished results in wood...it just takes longer since it's done by hand.

Anyway, that conventional wisdom has been inherited into the random orbital (DA) market for detailing, it seems. However, there are many threads here and on other forums where people have gotten excellent finished results using the Rupes 21 alone, or the Rupes 15 alone. Either one has produced results that rival the other DAs with much smaller throws.

That would all seem to indicate that the throw--in and of itself--has no real bearing on the final finish. They all finish well, in the right hands. The throw of even the smallest throw DA is so large compared to the size of abrasive grains (and those grains are what do the polishing) that it wouldn't seem to make a great deal of sense that the throw enters into the finish quality.

I'm not aware of anyone doing a controlled scientific test of large versus smaller throw relative to surface finish, and it would be a hard test to be sure everything else (amount of abrasive, pad, pressure, angle, arm speed, orbital speed, etc) was constant. So I guess you'll have to make the call based on what you've read.

[SR99]

An additional bit of info on this, in case you've not already seen it:
Rupes LHR 21ES Random Orbital Polisher - Features & Benefits - Machine Polishing & Sanding - Autopia (http://www.autopia.org/forum/topic/128711-rupes-lhr-21es-random-orbital-polisher-features-benefits/)
See the section titled "The Bigfoot can create a dazzling finish" in post #1 from Kevin Brown. BTW, the rest of the thread, while extremely long, is packed with information.