For sanding and polishing a gloss coat, is a quality random orbital sander as effective as a rotary sander/polisher? Since, as I understand, you really don’t want to generate any real heat in this process, does a random orbital produce as good a finish? I have both, but was just wondering what people that have more experience than I have think. This is just for amateur work, not production work.
Most guys go thru the process with a 7" sander/polisher. (Rotary). Depends on how good the gloss coat that you put down over a sanded hotcoat that has no swirls. Then go thru the grits with no swirls in a sanded gloss. Then you are ready to polish with #2 polish. Where an orbital comes into play is when you are having trouble leaving swirls. One of the reason to go over the board after each grit by hand with water. The swirls show better. An Orbital can get rid of problem swirls and works well for polishing. I don’t use compound unless I got some issue in my sanded Gloss.
If you sand your blank flat and lam tight a good random orbital is only tool you need.
Even many pro move to modern orbital or roto orbital sanders, like those used in many other industries for long time. Plus you can collect sanding particules by connected a shop vac on sander.
As my old Ethics professor used to say, “that depends”.
First off, heat buildup has a lot to do with how sharp your sandpaper is. Sharp paper cuts quickly* and doesn’t make anywhere near the heat (through friction) that dull, worn out paper does. And paper is cheap, compared to redoing things.
Next, is it the right paper/abrasive? Some common discs are made of a grit material that is really fine for sanding softwood, woodworking hobbyist grade. Resin is harder stuff and it’ll dull the junk paper fast, overpower the adhesive that holds said grit material to the discs and you wind up with paper that has no grit in spots and just gets hot. And again, the good stuff cuts fast* and efficiently.
Likewise polish. The right stuff is fast* and efficient, the wrong stuff does indeed get hot and just works badly.
Essentially, if you’re getting heat buildup, your abrasive is wrong. Change it.
Now, you’ll notice I wrote ‘fast*’ in several places. That’s because fast is good for production. But you can do a lot of damage fast too unless you’re pretty comfortable with the tools, good with them and very attentive.
Doing production work? The big variable speed Milwaukee sander/grinder with one of several backing pads was and is my friend, but I first spent months grinding boats over the years, with it and other lesser disc sander/grinders, wore out a few. When you fuc# up with one on a boat you can just fill with Bondo and paint over it. Surfboard gloss? Not so much. You can go through gloss, and hotcoat, and glass and be into the foam before you know it, a moment’s inattention.
Guess how I figured that one out.
Doing production ding repairs for fun and profit. Yeah, I used it. I had the thing, I was good with it and I was focussed. But there was also a place for the random orbit sander, or the plain old half sheet or quarter sheet orbital sander, doing finer work. Or, and yes for gloss work, wet and dry paper and a lot of water and by hand, no sanding blocks or power.
Doing a gloss, for yourself? Just a lot of sandpaper, several flavors, hand work and patience. Relax. Enjoy the work.
It’s supposed to be fun, after all. Not fast. Otherwise, you’d go out and buy a board somebody else made.
hope that’s of use
doc…
Here’s a tip for anyone who will listen; Use Indasa sandpaper. Takes 2-3 sheets of 3M to do what it takes one sheet of Indasa to do in the same grit. They make all the same products in abrasives. circular Velcro, seven inch peel & stick, wet & dry etc. no matter what sander, you will have better results. Most suppliers carry it or can get it. South Shore has the Orbital Velcro disks.
!,
You’ll need a rotary sander/polisher to buff a high gloss finish, not going to happen with a random orbit or even a combo like the Festool; the rpm isn’t there. Matte finishes are OK using an RO, but considering a max disk size of 6", mid’s and LB’s are a problem. RO’s are safer and easier on all rails especially if foam backed. It takes a lot of experience to use a heavy rotary sander on non-flat surfaces so I would advise using a rotary on the flats and RO on rails and bottom contours. There are some that really like the old 1/2-sheet sanders instead of RO on rails and they get very good results. But as Doc says it’s all about matching the paper to the work.
Takes a little effort to get used to a rotary sander, but one can be had for as little as $40 at Harbor Freight. Flex Pad about $35. Throw in a wool bonnet, a can of 3M77 and some Indasa sand paper . For less than $100 you’re good to go.