I’m real new at all this and was wondering why you would use a random orbital sander versus a half-sheet flat-bed sander? Seems the random orbital sander would be prone to leaving “scallops”; even if very slight. Fixing to buy a sander, so would appreciate advice.
Thanks much,
Tom Brown
Replies
On the contrary, a random orbit sander works with an eliptical bearing. With each pass it basicly covers its own tracks. This is an essential for good sanding particularly if you are just starting out. It takes time to identify cross grain sands and swirls that can be left by quarter sheet sanders. You should absolutely get a random orbit and use a block and progressive grits of sandpaper to get into the corners. Good Luck
Well, FWW had an article about ROS a couple of years back and showed the scratch patterns of various sanders.
For the test, they ran the sanders one pass down a sheet of plexiglass and showed the scratch marks. Some of the sanders, like the Bosch had an incredibly smooth scratch pattern that showed no individual sanding marks. But the idea is to go back and forth and up and down with the sander to eliminate any scratch marks.
While I don't have a flat sheet half sander, I believe that they just go back in forth in one direction and you have to use your arm motion to create the "randomness."
I love my ROS. Although I really love the little curved shavings from my Lie-Nielsen smoothing plane, I'm not proficient enough with it to trust it over a good sander hooked up to a shop vac! The card scraper is really nice too, but if you aren't careful, those seductive little curls will de-flatten your work. Okay... I admit it, I need more practice with hand planes!
My guess is, once you use an ROS you won't look back, if it's a good one. Tips:
jump,
While your looking at sanders, do yourself a favor and make yourself a couple of hand sanders. Just shape out a block of wood on the bandsaw and put some 1/4" cork board on the bottom. I use double stick tape to attach the sand paper to the block. What surprised me about the hand sanding was that in many situations its less work than pushing around the power sanders.
Before there were random orbit sanders, the Rockwell 505 was the standard in a lot of shops. These type of sanders leave little spring shaped marks that are very visible. The RO sanders are a big improvement but they can still leave marks. People love to pull a trigger but you will save a lot of expense and get a better job with just a hand sanding block. In most cases, you'll have to do that anyway, so why bother with a preceding step? I use my RO for paint jobs and I have the right angle PC that I use a polishing bonnet on for auto work but I just go with a hand block for most of my woodworking.
Beat it to fit / Paint it to match
I started out with a flatbed sander and the 1/4 sheet sander. Later switching to a Portercable variable speed ROS. You will get better results in my opinion with a ROS and some degree of dust pickup. I recently purchased the Festool ETS/3 (3mm pattern) and it is incredible picks up dust the best I've ever seen. I have a Portercable Variable Speed ROS with little use getting ready to go into the classifieds if your interested. If you are going to buy new, I'd go festool! Just my two cents worth.
If it moves, tax it. If it keeps moving, regulate it.
And if it stops moving, subsidize it.
I'm not sure I understand why you thing the random-orbital sander will leave "scallops." In any case, as the others have said, a random-orbital sander leaves a surface that is flat and smooth, but with some cross-grain scratches.
If I can get away with it, I will hand-plane a surface, and then, if necessary, hand-sand with P220 paper on a sanding block. If the wood is not amenable to hand planing, I will use the random-orbital sander up to P220, and then once again hand-sand with P220.
The random-orbital sander is especially good at sanding film finishes, since they have no grain.
-Steve
steve and everybody,
some of you may recall an article in our beloved fww which stated that the "swirl" marks left by 1/2 sheet, 1/4 sheet and random orbital sanders was due to an abrasive granule left from a previous lower grit abrasive. the article went on to recommend that one should thoroughly brush or blow off the work and the sander prior to moving up the grit. i have done this religiously since reading the story. i have had little to no trouble with those spring-shaped swirl marks since.
eef
I have also found that when starting a new sheet, if I run the sander over the edge of a piece of scrap, this reduces the incidence of "loose grit" marks as the loosest bits come off almost immediately.
I gave my 1/4 sheet sander to my FIL. If he is smart, he will give it to someone else. :>) I've been through Porter Cable (OK).. Bosch (I hate the dust collector adapter as you basically have to tape the hose to it and the catches for it come loose while sanding if you put any pressure on them) and ended up with the new Milwaukee for $55 which has leaves an excellent pattern and excellent dust pick-up. The Ridgid 5" is not bad either for around the same price.
I also have a Ridgid 6" which is excellent and this model was made for Ridgid by Metabo in Germany. The current one's are made in China even though same design. I cannot say if the motor is the same. And of course the Festool which is very expensive. I do not personally see a difference in the pattern it leaves compared to the others. They say the dust is excellent but I consider the Milwaukee dust collection excellent also and I could buy 3 of those (which I now have two) for the price of the FT which allows me to not have to change paper on a run.
Sarge..
Edited 5/22/2009 9:30 am ET by SARGEgrinder47
ripfence1 is absoluty correct. A good wood worker doesn't even need a half sheet sander in his shop. Takes up too much storage space. ;-)
+1 for doing it by hand unless there's a huge amount of sanding. For the record, recent 1/4 and 1/2 sheet sanders have dust collection through the pad; they come with a plastic gizmo for piercing holes in the paper. I have a 1/4 sheeter I got for doing stairs, and I have to say it does the job no worse than the average ROS, with minimal scratching -- on stairs. I haven't used it on furniture. BTW they're all orbital, just not all random.
Jim
If you value your time, you will find that the random orbit sander will cut a lot faster than the cut sheet sanders, due to a larger motion, but they are not all equal in this respect.
I first saw Norm using the ROS many years ago and thought that he was crazy. How could this gizmo possibly leave a swirl free finish? I was a hand sander then. I finally bought into power sanding around 25 years ago. I still hand sand with the grain for the final pass, but the random orbiters really do a good job.
Now I own both 1/4-sheet and 5" ROS with hook and loop. I find the 5" soooo much nicer to use than the 1/4-sheet. With the 1/4-sheet, you have to tear the paper to fit, fiddle around with the clamping mechanism, then poke holes in the paper for dust collection (if you remember where you put the plastic doohickey that pokes the holes). It's so much faster and convenient to just peel off and stick on a new sanding disk. Sanding isn't much fun anyway, so spend your money/time on a nice ROS. You'll be glad you did.
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