Sandpaper girts

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Forum topic by Beginningwoodworker posted 09-10-2010 11:04 PM 1296 views 0 times favorited 15 replies Add to Favorites Watch
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13347 posts in 3092 days

09-10-2010 11:04 PM

Topic tags/keywords: sanding finishing sander question

I am wondering what grit of sandpaper do I need? My shop teacher taught me that I use 80 grit as my only sandpaper, he said by keep using it. It becomes a finder girt of paper. Is their any truth to this? I as though that you more than one girt till to get to 220.

15 replies so far

View PurpLev's profile


8523 posts in 3068 days

#1 posted 09-10-2010 11:11 PM

80 grit paper will ALWAYS stay 80 grit paper. the scratch marks will always stay LARGE, although as it gets used – it won’t make AS MANY scratch marks as NEW , but they will still be large marks.

I have 80 (for really rough work), 100, 150, 220, and 400.

Since I started working with scrapers and hand planes I never used sand paper except in 2 cases:

1. sharpening blades
2. finishing (using 220 for prep, and 400 between coats)

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View docholladay's profile


1287 posts in 2478 days

#2 posted 09-10-2010 11:17 PM

Sounds to me like your shop teacher didn’t have any budget to buy sandpaper so that was his explanation. Can’t say that I have heard that one before. There is probably a small amount of truth, but I don’t think that 80 grit paper will ever become 220 grit. It will completely wear out and disintegrate long before the abrasive would ever break down that far. Besides, before the abrasive would break down to that fine, it would actually simply fall off of the paper. You eventually would be rubbing your project with plain paper. I actually have heard of people using the brown paper like used for paper grocery bags for rubbing out a finish to create a satin finish. Can’t say that I have ever tried it though. I would agree with your shop teacher that you probably do not need to have, nor go through ever individual grit of abrasive. Personally, I usually follow the following steps. I usually start with 100 grit (unless I need to be very agressive, then I might go as far as 60 grit). Then I go to 150 or 180 grit. Next I will go with 220 grit. For most projects, I would stop there. For some items or if I want a polished finish, I then would go to 400 grit followed by a very fine woven abrasive pad (I don’t like steel wool because it often leaves steel fibers on the project that can create finish problems later). If I want to polish even further at that point, I will use a polishing wheel loaded with a polishing compound.

-- Hey, woodworking ain't brain surgery. Just do something and keep trying till you get it. Doc

View docholladay's profile


1287 posts in 2478 days

#3 posted 09-10-2010 11:20 PM

Like Purplev said, you can eliminate use of a lot of sandpaper with scrapers for cabinet projects, however, it is so easy to sand your lathe projects right on the lathe, I usually prefer to sand my turning projects. I have to admit that my turning technique is not good enough that some amount of sanding is going to be required.

-- Hey, woodworking ain't brain surgery. Just do something and keep trying till you get it. Doc

View Beginningwoodworker's profile


13347 posts in 3092 days

#4 posted 09-10-2010 11:21 PM

I have a DeWalt ROS Sander so I like to use it.

View Catspaw's profile


236 posts in 3235 days

#5 posted 09-11-2010 12:00 AM

80 grit will remove some material. 120 will smooth the 80 grit marks (if you have the time you might go to 100 grit before the 120.) Beyond that you really don’t need any finer grit (like if you’re applying urethane.) Maybe, just, maybe, I suppose you might use 150 or 220. But, the build you get with more than one coat of urethane is far thicker than the surface 120 leaves behind.

If you want a real smooth finish on wood you do it in the finish not the wood. On the occasion I paint something, I like to prime it, sand with 220, then paint.

If you’re going natural, then you’d use the finer grits. A protective finish such as an natural oil or something doesn’t neccessarily build like a polymer so it’s not going to fill anything.

Also, most people use their sand paper way too long. You may think it’s still working because it feels rough, but, it probably isn’t. Change to a fresh peice to see the difference. If it’s noticable, throw the old peice out.

-- arborial reconfiguration specialist

View MOJOE's profile


548 posts in 2688 days

#6 posted 09-11-2010 04:45 PM

As I understand it, the grit deals with the number of particles per square inch of surface…, even though 80 girt paper will wear down, there will still be 80 partilcles embedded on the paper, so they will still be larger particles with a certain amount of space between. Since the square inch reference stays the same, the only way to fit more particles (180, 220, 400, etc.) is to make the particles finer. In doing so, the free space between particles is lessened and therefore, the scratch marks are finer. The next finer grit will remove the previous scratches and so on until the material is smooth (to the human eye and touch) as there will always be scratches, after a certain point, we just can’t notice them.

-- Measuring twice and cutting once only works if you read the tape correctly!

View Greedo's profile


470 posts in 2380 days

#7 posted 09-11-2010 07:51 PM

i do think there is a limited truth to this, used 80 grit paper will sand like 120 grit paper, only less effective since even though the 80 grit particles end up reaching the size of the 120 grit ones, there are less of them and the sharp edges have worn down so it won’t go as fast. you can’t say 80 grit stays 80 grit, on quality paper the particles wear down and become smaller. otherwise you could use sandpaper indefenately if you keep it clean.

btw i saw 20 grit sandpaper once, it’s basically rocks glued to paper

View Steven H's profile

Steven H

1117 posts in 2480 days

#8 posted 09-11-2010 08:55 PM

I think hes trying to say is that the more you use it, the more grit it will lose. Therefore it will become finer and worned out.

View rwyoung's profile


383 posts in 2891 days

#9 posted 09-12-2010 02:04 AM

Your shop teacher was either an “old timer” or learned from “old timers” that only had access to garnet sand paper. That stuff fractures down smaller and smaller as it wears out. So there is a tiny bit of truth to the use worn out 80 grit as 220 grid urban legend.

But modern AO and zirconium papers don’t do that. They will load up and stop cutting but they don’t fracture. Sterated papers will load up less quickly.

And to be quite honest, I sand as little as possible these days. If I can plane it or scrape it I’ll do that before I ever reach for the ROS and heven forbid the belt sander. I’d be willing to bet I’ve paid for a couple of my $25 rehabilitated smothing planes in unpurchased disks for the ROS. :) And my lungs feel a whole lot better without all that dust in the air.

-- Don't sweat the petty things and don't pet the sweaty things.

View Dark_Lightning's profile


2619 posts in 2528 days

#10 posted 09-12-2010 02:19 AM

80 grit only as a sanding technique is nonsense. As you can see, there is a fair amount of disagreement in the woodworking field on the usage and grits of sandpaper used. It all depends on what it is you want to do, and the sort of finish you want in the end. No matter how much you use 80 grit, there will still be one “hill” left somewhere on the sheet, digging gouges.

Generally speaking, 220 is as fine as you will need to go.

That said, I personally have sanded as fine as 400 grit, depending on the project.

I seem to agree with Jarrod right up to the burnishing part. I’m not sure I understand what you’re talking about there, Jarrod.

-- Random Orbital Nailer

View kosta's profile


946 posts in 2774 days

#11 posted 09-12-2010 04:30 AM

I usually use 120 grit then 150 grit then 220 grit and that works pretty good. After I have stained and finished a project I use steel wool to smooth out the finish

-- kosta Virginia Beach, VA

View Beginningwoodworker's profile


13347 posts in 3092 days

#12 posted 09-12-2010 06:11 AM

Yes my shop teacher was old school.

View Gator's profile


379 posts in 3095 days

#13 posted 09-12-2010 03:40 PM

I am by no means an expert, but have read a lot of articles and taken a few finishing courses to try and learn more about this, and the common message from all the professional finishers I have received ( and read about ) is NEVER go up in grit more than two stages on a project. If you are using 80 grit, your next grit should be 120, but never be more than 150, to a max of 220, and always use 180 before the 220. Anything higher than this is for polished finishes, or wet sanding between coats. Not following this guideline will result in more sanding to eliminate the sanding marks left behind from the smaller/ heavier grit paper, and they will almost always be visible after you apply the finish.

If your shop teacher only builds swing sets and barn doors, then he is correct, 80 grit is all you need, but for anything else, take the advice of all the other people that posted replies, there is a pile of knowledge here.


-- Master designer of precision sawdust and one of a kind slivers.

View Beginningwoodworker's profile


13347 posts in 3092 days

#14 posted 09-12-2010 08:52 PM

I may go back to a hand plane finish.

View Roz's profile


1693 posts in 3206 days

#15 posted 09-14-2010 06:36 PM

That is definitely a myth. I start with 80 grit being careful not to hit any details or corners with it. Then move to a 120 or 150 grit and finish with 220 grit unless refinishing a floor. For floors, I use 40, 80, and 100 to 150. The surface needs to be a little more course to insure adhesion of the finish. I prefer an orbital sander. I use a fixed disk sander with 100 grit and the belt with 80 grit.

-- Terry Roswell, L.A. (Lower Alabama) "Life is what happens to you when you are making other plans."

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