From a woodworking/finishing aspect, both the 3/16″ and 3/32″ are good for sanding wood. In some instances, you may need to use a lighter touch with the 3/16″
Most random orbital sanders used by DIYers take 5-inch discs, which is the best size for fine sanding without creating any swirl marks or scratches. However, you'll also find sanders that use 6-inch discs.
For general DIYers, a good place to start is with a basic random-orbit sander—a square 1/4-sheet sander or round model. If you do a lot of furniture work, adding a detail random-orbit sander with a pointed, contoured head might be a good second tool to own.
Choosing the right sander for the job
If you're looking to sand wooden joists or beams, you'll need a belt sander; this is the most powerful sander available and is your best option for heavy-duty tasks. If you plan to sand any curved surfaces you should look for an orbital sander.
Firstly, a final hand sand before finishing will always give a better finish than ending with a power sander as, no matter how fine a grit you use, there will always be scratch marks left by the power tool. You can also fine tune spots that may need extra care, which could be too small for a power sander.
A: Yes, random orbital sanders can be a worthwhile investment. They're precise and leave a smooth sanded surface behind while also being powerful enough to remove a lot of material in a short period of time with little strain on behalf of the one using it.
This “random” motion results in a smoother finish, without the swirl pattern that can come from standard orbital sanders that only move in a circular motion. Random orbital sanders are extremely efficient for large projects.
If you are only going to buy ONE sander, I would say the random orbital is your best option since it goes from course to fine sanding easily. If you are doing a lot of fine finishing work and want to save some money (and not have to lift such a heavy sander) then a finishing sander is worth the small investment.
Don't press down on the sander very hard at all; only press down hard enough so that it stays flat on the surface. Pressing down too hard can cause those dreaded swirl marks, as well as cause unevenness in the wood.
Besides operating at no less than 90 PSI of air pressure, random orbital sanders should run with a minimum speed of 10,000 RPM. If you run the sander at a slower speed than this, swirl marks MAY also appear. But if you drop below 90 PSI at any time during your orbital sanding process, you WILL get swirl marks.
Anything in the region of 80 to 100 is considered “medium” and suited to final shaping or removing planing or saw marks. Fine sandpaper is 120-220 grit, and is good for a final sanding before applying a finish, while 440 grit and above is for the finest finishes or sanding between coats of paint.
Random orbital sanders have two major things in common with rotary sanders: (1) they use a circular pad, and (2) disk moves in rapid circles. But the 'random' part of the name tells you the major thing that sets it apart: random orbital sanders vibrate.
Each grain of sand on the sandpaper moves in a small circle on your workspace to remove material and smooth uneven surfaces. Orbital sanders come in a range of shapes and sizes. A detail sander is a type of orbital sander that has a pointed, triangular base suited for sanding into corners and tight spaces.
We recommend you purchase a random-orbit sander as your first power sander. Random-orbit sanders can handle nearly any DIY task. Sure, they won't smooth gnarly wood as quickly as a belt sander or sand details like an oscillating multitool, but they can do just about anything when paired with the right sandpaper grit.
The biggest disadvantage of random-orbit sanders is their round sanding surface, which makes it impossible to get in corners. Also, they can remove too much material if held in place too long.
Dust Clogging
If your random orbital sander doesn't have an effective dust collector built in, the sandpaper can get clogged up and impede the performance of the machine. Not only will you have to sand a lot longer to get the same results, but clogged sandpaper builds up heat and goes dull more quickly.
Disc sanders are best if used for more abrasive, rougher work where a lot of material needs to be scraped away in order to provide a finer or smoother surface. A disc sander can easily strip paint or remove old varnish with ease, and it will save you a lot of time compared to trying to do these tasks manually.
Best For Small Jobs: BLACK+DECKER Random Orbit Sander
Even though it's not quite as powerful as other sanders, it still includes a built-in dust collection bag and a lock-on paddle switch to easily power it on and off.
Safety Rules
Don't wear loose clothing or gloves, keep long hair tied back. • Never adjust Sander or setup while Sander is running. • Never remove guard unless authorized by Technician or WRL Manager • Setups requiring anything other than the standard sander equipment must be approved by supervisor.
It's best to use a backing pad when wet sanding to achieve a uniform finish. Instead of using small circles as you would with dry sanding, wet sand in a straight line, first horizontally and then vertically.
Wet sanding is a sanding process that uses water or another liquid as lubrication to wash away grit particles. Without the liquid, the sandpaper can build up with material, causing scratches that ruin the finish. In general, the best liquid to use for most materials is water with a little bit of detergent in it.