Random Orbital Sander vs Sheet Sander
No matter what the advertising says, hand sanding has not been eliminated and when working with shapes and contours it [hand sanding] is really the only way to get the job done. But there are times when the job is big or the amount of material to be removed so much, that a power tool is required. Question is "What's the best sander to use?"
If its rough work, a lot of material needs to be removed or shaping wood is involved then the belt sander is the tool of choice. But more often than not, what the woodworker, carpenter or handyman needs is to smooth a surface, remove old finish or sand between coats during final finishing. These tasks bring us to two types of hand-held power sanders: The Random Orbital sander and the sheet sander.
The random orbital sander, the past ten years, become one of the most common hand-held power tools in the shop. They've come down in price a bit, they get the job done quickly and leave behind very few sanding marks and advances in technology made them a good choice regardless of skill level.
Technology has not ignored the sheet sander, which has been around for years. Down-sized from a tool that used a half-sheet of sandpaper to a quarter sheet and made more ergonomically designed to fit into the palm of the hand (hence the name "palm sander") they are a very popular addition to the toolbox.
How they work
Sheet sanders are designed to work with partial sheets of standard sandpaper, whereas random orbital sanders require round disks, typically attached to the sander base with either adhesive or hook-and-loop type fasteners. The ability to use standard sandpaper is a major advantage for sheet sanders since the sandpaper can be purchased almost anywhere.
Operation of a sheet sander is pretty straight-forwared. Sandpaper sheets are cut into halves or quarters and are then securely clamped onto the flat base of the sander. The sander uses a motor that moves the sanding pad in a back-and-forth-circular motion at high speed. Big sheet sanders, the half-sheet variety can remove remove material fairly easily and work good on large flat surfaces. Their smaller cousins (1/4 sheet sanders) however do not remove as much material, mainly because the sanding surface is much smaller. But that can be a good thing. It is a great tool for sanding between coats of paint or finish because there is less chance of sanding through the finish.
Sheet sander pads (and the sandpaper on them) are square, so the tool can get into corners.
The motor on a Orbital sander moves the pad in a motion similar to the sheet sander, but in "random" is the operative term. The random orbital sander used an offset drive bearing that causes the pad to also move in an elliptical pattern. These pad movements are used in combination, randomly of course to help reduce the swirls that a non-random sheet sander might leave behind.
Mechanics aside, a mojor difference is in the sanding medium. Most random orbital sanders use sanding disks, typically in a 5-inch diameter. They are attached to the sander's pad using hook & loop connections. The sanding disks have holes in them that match-up with the dust collection holes in the sander's pad. Sanding disks are available in a number of grits, the most commonly available are 60 (coarse) through 220 (very fine). The disks can be expensive and there are times when the supply is limited.
Pros and Cons
|Random Orbital Sander
Excellent at removing material
Changing grits not necessary to get good results
Easy to change hook & loop disks
Superior dust collection
Some units have variable speeds
Less hand fatigue
More expensive to buy and operate
Sanding disks sometimes hard to find
Not for sanding between coats
Aggresive power can ruin a piece in seconds
Hook & Loop on pad can get dirty and fail to hold sanding disk
Sanding pad can become damaged - affects sanding quality
Circular pads prevent working in corners/tight spaces
|Palm Sheet Sander
Sheet Sandpaper in varying grit readily available
Square pad fits into corners
Fits into palm of hand
Sandpaper clamps down - doesn't come loose.
Excellent for sanding between coats
Poor at removing material
Leaves swirls in finish
Hand and wrist pain from use
Hand numbness with extended use
Sheet sandpaper tears
Changing sandpaper is time consuming
Holes have to be punched in sandpaper for dust collection
How to Use a Sheet Sander
Work with the grain as much as possible. Swirl patterns emerge when working against the grain. Keep the sander moving all the time. Sand using progressively finer grits of sandpaper. This is almost a must to eliminate swirl marks left behind by the sanding pad's motion. A follow-up with hand-sanding for the final touch is required for a perfect finish.
How to Use a Random Orbital Sander
When working with a random orbital sander, keep the sander moving with the grain of the material. Leaving the sander in one place may cause an uneven finish.
Because both sanders are light and easy to handle, there is a tendency to round over the edges. Avoid the urge. If an eased edge is desired, sand the sides to create a consistent and distinct chamfer on the edge rather than rounding it over the face of the piece.
What to look for when buying
When shopping around, Compare apples to apples. If you are in the market for a sheet sander, compare models of sheet sanders. Don't compare sheet sanders to random obital sanders. The decision should have been made before you started to shop based largely on need.
Comfort and feel comes first. It should feel balanced comfortable in your hand. It is best if you can turn the sander on and see how much it vibrates and how much noise it makes. A lot can be told about craftsmanship by these two factors. by type. tions. All sanders vibrate, but an excessively vibrating sander can really wear on the operator's hand and wrist when working on large sanding projects.
Look for extra features but don't waste your money on them. Example: Some higher-end random orbital sanders have variable speed controls in woodworking applications, this has little practical use. But a trigger lock, to lock the power on when in use reduces hand fatigue.
Which should you Buy
A serious woodworking enthusiast or professional is more likely to want both a random orbital and sheet sander. Each has its benefits each has it's weaknesses. But combining the two, you can't go wrong.
For beginners that ennvision loads of weekend woodworking projects, furniture refinishing and small remodeling tasks it would be prudent to go with a random orbital sander. The few extra bucks paid are easily off-set by the tool's versatility. Having a sheet sander as the only power sander is probably fine for someone who only occasionally needs a power sander.
And when you get right down to it you just can't beat the finish achieved by hand sanding.