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Sanding out scratches made from sander.

6K views 17 replies 14 participants last post by  shoot summ 
#1 · (Edited by Moderator)
I am down to a 180 sandpaper and still see scratches from my 80 grit sandpaper. Am I wasting my time going to a 220 or should I keep sanding with the 180.
 

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#4 ·
Did you sand in between grits like 120? Then 150? Before 180?

If you try to sand 80 scratches with 180 grit, it will take much longer time. Sand with 120 grit until 80 grit scratches are gone. Sand with 150 until 120 scratches are gone. Then use 180 grit. Use block and hand sand lightly with grain before sanding with next grit.

Rules are sand with next grit until former grit scratches are gone and do not skip grits.
 
#9 ·
It sounds like to need to spend more time on the "in-between" grits. Go back to 80 and make sure you've really gotten out all of the scratches from the belt sander. Then go 100, 120, 150,180 then 220. I like to do 220 by hand with the grain. I also sometimes wet the board between grits. It shows up any rogue scratches and makes the grain fuzz stand up so the next grit can get it. Once it's dry, you can continue sanding. Like most people, I don't enjoy sanding, but there are no shortcuts if you want a perfect finish.
 
#10 · (Edited)
To answer your original question, yes, you are wasting your time and a heck of a lot of sandpaper in the process.

I say go back to 80 grit and make sure you got all the 60 grit scratches out. Then climb through the grits as others suggested. You just went through the grits too fast.
What was your surface like when you started that you needed with such a low grit?
 
#12 · (Edited)
Stop and take a deep breath.

First and to solve your problem, call a local cabinet shop. Ask if they know of any one that rents time on a wide belt sander.

My local guy charges $80 per hour with a ½ hour minimum. I've never been able to accumulate enough material that went over the ½ hour. From your description of the problems it sounds as though you are well over the $40 in sandpaper alone. Allow your guy to sand both surfaces as it will make it easier to finish the underside of the table top. Pay the guy in cash. His wife/girl friend will love it when he takes her out for dinner. (The cash goes into his pocket and not into the accounting system.)

When you use the final wide belt it probably be to 120 grit. You could do 180 grit if you are going to stain or 220 grit if just polyurethane. Regardless do some sanding on the end grain to 400 or 600 grit. That way the ends of the table will look the same as the top after staining.

With machined lumber I can not imagine using 80 grit. If the glue up was that uneven that 40 grit was needed, it would have been better to rip the table top apart and start over with some dowel joinery.

One other comment. A 48 inch wide table is HUGE. It will be exceptionally difficult to reach across during use. Even with kiln dried lumber and used indoors, you can expect ½ inch movement due to changes in ambient humidity. You have to allow for this movement, as a minimum and closer to ¾ inch, when attaching the table top to the supporting frame.
 
#16 ·
Go back with the belt sander with 80 and 120 grit before you go to the orbital.
I would use my cabinet/card scraper. Love it, don't use much sand paper anymore.
All outstanding suggestions.

I will add some of mine:

A) Your photo shows the 80 grit RO swirls, so as you stated, 120 grit should be your start point if you are going to resolve this yourself.

B) I’ll also point out that if you go to your local cabinet shop, listen to their advice and their 220 grit will easily resolve your swirls in no time.

C) I’ma big fan of General Finishes’ rub-on penetrating oil-polyurethane finishes, and 220 grit is their max suggestion.

D) As with all of our tools, be careful to let the tool do its work, do not force it. This the cause of your swirls coupled with the previous comments about cross-contamination of abrasives when changing grits. Pressing down on the sander guarantees what you now have, so back way off, let the weight of the tool be all that holds it to the workpiece.

E) You can remove the swirls and move straight to finishing with no more sanding if you use a smoothing plane.
 
#15 ·
Hey Del50man
I began my woodworking life knowing nothing. I used rough cut wood, and tried sanding it with an old Craftsman vibrating 4x6" block sander. I never used a belt sander for years. My first belt sanding project had cross grain scratches and gouges from not learning to float the belt sander. So I know a lot about fixing sanding mistakes,
I assume that maybe you started with unsurfaced wood, as 40 grit belt sander paper is just not something to use on any piece of finished furniture. You will get grooves from the stones used in 40 grit that can only be removed by sanding down to the bottom of the groove the 40 grit size stones leave. It doesn't matter what you do to the surface of the wood until you remove the grooves from the 40 grit. I would go back to a 100 grit belt, and remove the deep scratches. It will take a while - and then go to a 120 belt, and then an 80 grit orbital. I would want to see any grooves gone by the time you switch over to the orbital. I would go next to 100 orbital, and then 150. by that time you should see a markless top. I would then go to 180 for a finish sand. 220 if you really want. All sandpaper makes marks. It's just that when you use really fine paper, the marks seem to disappear, but they are still there.
The beauty of woodworking is you can almost always fix your mistakes. Remember to go with the grain using your beltsander, as going crossgrain will make an even harder mess to fix. Just understand that you may need to spend a few more hours relearning to sand. At this point you need to stay with power, as you will probably have to take off at least a 1/16" to get the deep scratches out. Do not waste time trying to hand sand. I personally love to sand, as it makes my mind quit thinking about everything else but the wood surface. I have spent hours sanding table slabs because I no longer have a 48" 3 drum belt sander.
Good luck, and don't worry about making your table a bit thinner. You will be the only one who knows.
ja
 
#17 ·
That sounds like a big farmhouse table and a lot of work to make it smooth.
Have you thought about just leaving it as it is to give the table a rustic look? It will add character for sure.
Unless it is really out of whack I would take it outside and hit it with some big chain links and rocks to give it some nice markings and then finish it.

If its a personal project, make a mental note of any mistakes made and move on.
If its for business and the customer wants a certain look then you definitely need to drive on.
 
#18 ·
I'll add my opinion.

I don't see as many swirls as I see straight scratches across the grain. Did you run the belt sander with the grain, or across the grain?

40 grit is too coarse, so is 60 unless you are trying to resolve some surface issues.

Go back to the belt sander, running with the grain, 80, 100, then 120 grit.

Use the orbital with the grain 150, 180, 220.

Let the sander float and do its work, don't bear down on it.

They say you should sand 2x as much as you did with the previous grit. I don't really buy into 2x compounding, but I do think you need to be diligent about sanding as much(or a little more) with the subsequent grits as you did with the previous grit.
 

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