does the type of sander make a difference?

I am refinishing stained and I think varnished cabinets. Read FHB article “Refinish Your Cabinets”, very informative.I am sanding the doors and was concerened that the sander I am using may be the wrong one. It is a rectangular shape. Should I be using a circular shape? Any difference in the finished product?
Replies
No difference, but random orbit may be the best type, the choice of sandpaper and not skipping grits is most important.
Mark is absolutely correct in his advice to work through the grits properly.
Here's my 2 cents on sanders. I have found sanders come in three types: In line (like belt sanders and rectangular pad sanders), random orbital (most common detail sander), and circular (like floor edgers). Some combine functions of circular and random orbital like the Festool Rotex sanders.
The basic thing to remember is that sandpaper is abrating or scratching the surface.Course grits are nice to take material off quickly, but you pay a price for this effeciency in the final finish--if you don't work through the grits. Each abrasion is a gouge or scratch in the wood fibers; the courser the grit, the deeper the gouge. Gouges are hard to work out if you skip grit because the finer papers won't reach into the deep valleys of prior courser grit scratches; particularly when the sander is working across the wood grain.
This is most apparent in the final product if you use pigmented wiping stains (like common Minwax). These are probably the most common type stains. They have pigmented particals that are suspended in a vechilce (like mineral spirits in the case of Minwax), acetone, water, etc. The stain's dark pigment particals lodge in the deeper scratches and wipe off on the smooth top surface. It can give a really foul the look of an othewise beatifully grained wood. TSometimes you will see (in the case of random orbital sanders work that is not done properly) what some people call "pig tails" all over the surface. They are evidence of the deep orbital scratches spiraling away as the sander is moved across the surface. they were never worked out before staining and sealing.
Problem is sometimes you cannot see the microscopic scratches until you apply the stain; particularly on light colored hardwoods. This is why some people like to rough out with a random orbital and then work through the finer grits with an in-line sander (like the LS130) or even a cabinet sraper, always moving with the grain. It's a art. My advice is experiment with a scrap of the same wood (or one of the backsides of your cabinet doors) until you're satisfed your entire process (strip, rough, sand, seal) works well. Then stick to it for the rest of the job.
BTW, sanding sealers or wood stain conditioners really help on most hardwoods and softwoods. I recommend experimenting with them. I've done some custom stain matching jobs that would not have been successful without this step.
Good luck!
Isn't there a fourth type, the oscillating type? I have the Fein multi tool and the only thing it does is oscillate. For detail work I have never seen anything as efficient.
I stand corrected
I believe you're correct. We definitley should add that to the list.
I have the Fein multi-master as well... and agree that it works great; although you can still get 'pigtails' as you move the sander around the worked surface. Working through the grits is still prudent here as well. I would say that the best way eliminate the risk of pigtailing is to use sanders that work strictly with the grain. Every time you cross grain, whether it be by a rotary, orbiting or oscillation stroke, you risk a nasty guoge in the grain that is harder to work out for a fine, stain-grade finish.
BTW, the Festool RO90, fitted with the delta head, provides a similar efficiency to the Multimaster in detail work . In fact with the rotary action activated, I find I can remove more material, quicker. Then I switch to random orbit and get similar results to the oscillaiting Fein tool. The other plus to the RO90 is the better assortment of stock sanding papers available.
The rectangular sander you have is likely a "finishing sander" and should be a pretty good choice for your work, as it can get into corners pretty well and is not so aggressive as to mess things up if you slip a bit.
Generally these are "orbital", meaning the sandpaper is moved slightly down then left then up then right in a sort of circle. Some such sanders have a setting (a lever on the side) that changes from "orbital" to just up/down, so you can use that setting for the last few passes and not leave sanding marks (if you take care to sand with the grain). Such a sander is pretty good for furniture finishing.
The downside is that such sanders are not good for taking off a lot of material (if you need to remove an existing finish, eg), and they aren't as good of a choice for finishes without a grain.
You need to discern the movement pattern of the sander. That is what is important. The shape of the base doesn't mean squat in terms of how the wood is smoothed. The shape only affects how close to an inside corner it will fit.
If what you have is an older model sander, perhaps scored at a garage sale for a buck, then throw it away. The newer random orbit sanders that are now available are vastly superior. As for most tools, you get what you pay for.
Another consideration... If your sander does not have efficient dust management then throw it away. Belive me, life's too short to be breathing or be coated in all that fine dust.
more than the movement pattern
Not only should you discern the movement , but if it is a radom orbit or osillating type of sander, you should consider the speed and stroke of that sander. Some of the Festool sanders range from 5/64" to 3/16" stroke and range from 3,000 opm to 14,000 opm. The slower and longer the stroke across the grain, the more work it will take to work that scratch out.
Sanding and scraping is a labor intensive job. Seems today's tool manufacturer's have honed in on this fact and present every option under the sun to help overcome that labor in a special way. No longer can we say that a sander... is a sander...is a sander.