What's the finest grit sandpaper you use on plane soles?

[Mike Dowell]

Hey all, I still haven't decided on what my new plane purchase will be (reference a 2 page thread I started a few days ago), but last night, I was watching a youtube video where a guy from Lie Nielsen was setting up a brand new chisel. He said that their stuff comes really flat, but almost always needs a little tuning, and he mentioned that planes are no exception.

For fun today, I took my LV Apron plane and ran it across a 1200g diamond stone a couple dozen times. I discovered that it was not totally flat! I took it to some 320 grit paper on a granite block to get it flat, but then realized I had opened up the question well. How shiny/polished should the bottom of a plane be?

Also, I know the preferred method is to use a granite block with sandpaper, but one thing I noticed is that the paper does not sit perfectly flat on the granite. Because of this, as you move the plane around on the paper, it creates almost a ripple in the paper which leads the plane. What I notice is that the bottom is flat, except for the very outer 1/16" of the sole's circumference. That area is beveled up a slight bit. Normal?

[Patrick Chase]

Hey all, I still haven't decided on what my new plane purchase will be (reference a 2 page thread I started a few days ago), but last night, I was watching a youtube video where a guy from Lie Nielsen was setting up a brand new chisel. He said that their stuff comes really flat, but almost always needs a little tuning, and he mentioned that planes are no exception.

For fun today, I took my LV Apron plane and ran it across a 1200g diamond stone a couple dozen times. I discovered that it was not totally flat! I took it to some 320 grit paper on a granite block to get it flat, but then realized I had opened up the question well. How shiny/polished should the bottom of a plane be?

Are you sure your diamond stone is flat? Most of those are manufactured to about the same tolerance as LV's plane soles (on the order of a couple mils), so IMO it's a coin toss which one is "right".

Also, I suspect that you're fixing something that isn't really broken. A mil or two is not going to make any difference to a block plane.

Also, I know the preferred method is to use a granite block with sandpaper, but one thing I noticed is that the paper does not sit perfectly flat on the granite. Because of this, as you move the plane around on the paper, it creates almost a ripple in the paper which leads the plane. What I notice is that the bottom is flat, except for the very outer 1/16" of the sole's circumference. That area is beveled up a slight bit. Normal?

Typical, but not ideal. That's why a lot of people use loose SiC grit or glue down their sandpaper. As noted above I'd urge you to leave well enough alone. Those planes come more than flat enough, and if you don't have a fair bit of practice then you're likely to cause more trouble than you fix.

[Dan Barr]

I go from 240 thru 1400 or 1600. Anything after that is past the point of diminishing returns. Not saying I didnt put my norris and Spiers of Ayr smoothers on leather with flexcut (i just kinda got in the zone thinking about pursuing perfection). 1400 plus wax and the plane will almost run away. 😝

[Robert Hazelwood]

For flattening the sandpaper really needs to be stuck down firmly to the granite to prevent the dubbing you are describing. You can use spray adhesive or buy PSA (pressure sensitive adhesive) sandpaper. Even then, you can still get a small amount of dubbing due to the compressibility of the paper and grit- most noticeable on coarser grits. A small amount of dubbing is not a problem for most things but 1/16" seems excessive. The plane should still work fine but it will effectively function as though it is 1/8" shorter and narrower. A bevel on the front side of the sole can also tend to ride over any debris on the board you're planing and keep the blade from cutting.

As for what grit to finish on, I don't think it's terribly important except I don't trust the thicker sandpaper in lower grits to give a very flat result. For example, if I take a plane sole and flatten on 80 grit paper until it has a perfectly even scratch pattern, I can count on being surprised when I switch to 150 grit by remaining high spots. It seems the heavier grits can reach up into low spots a bit and scratch them evenly along with the rest. To be clear, the coarser grits will still make the sole flatter, but tend to mislead into thinking you're done prematurely. 80 grit does this and 150 does it somewhat less. By 220 grit things are pretty settled, and from there on it's just refining the scratch pattern. So I guess I'm saying I'd take it up to at least 220 grit for flatness sake, and I'd probably be tired of lapping by that point so 220 is where it would stay. Going to 400 or 600 may look nicer, but I don't think you'll notice a reduction in friction, and in either case the sole will get countless little scratches from use, which will only be more noticeable on the finely lapped sole.

[Jim Koepke]

As Patrick said, you are likely to do more damage than good with most planes.

As for an answer to your question, 360 grit is good enough for me.

My fortune was good a few years ago in being able to pick up a four foot hunk of granite from a monument maker (tombstone carver) for $25.

Granite on Horse.jpg

To keep the paper from bubbling or wrinkling it is helpful to use roll stock abrasives with a pressure sensitive adhesive backing.

The abrasive sheet is cleaned often with a large magnet wrapped in paper.

jtk

[Mike Dowell]

Well, I definitely did not do any harm. How would I harm it anyway? I guess the argument could be made if I took it to my 6" edge sander or something. I finished by rubbing the plane on an 800 grit diamond plate (because it's a small plane I could do this). After that, I sharpened up the blade. I noticed that although the blade is supposed to be 25 degrees, it was not. At least not according to my Veritas MKII honing rig. Anyway, I got it set up and it shaves like a dream. Good to know in the future, that a sole which is not perfectly flat is not really a problem.

By the way, I do have some PSA 3M stuff, but after a long process of scraping it off the granite the first time, I never used it again. Is there a trick to removing the paper? Additionally, I've never heard of cleaning the paper with a magnet. It seemed like I could dull the paper very quickly with metal, which to me is normal behavior.

[Ray Selinger]

On the UK woodworking forum a scientist posted that wood fiber size was 360 grit, so finer than that. Just passing that on.

[Robert Hazelwood]

Good to know in the future, that a sole which is not perfectly flat is not really a problem.

That is a little broad. It depends on particularly way in which a plane is not flat and how fine/accurate the plane is required to be. A finish smoother with a .002 concavity along its length would be a problem, for example. My comment was only referring to minor dubbing around the perimeter of the sole.

By the way, I do have some PSA 3M stuff, but after a long process of scraping it off the granite the first time, I never used it again. Is there a trick to removing the paper? Additionally, I've never heard of cleaning the paper with a magnet. It seemed like I could dull the paper very quickly with metal, which to me is normal behavior.

The only trick I know of is lots of acetone and a razorblade followed by scotchbite. Acetone dissolves the adhesive very quickly. But I agree that the strength of the PSA is a bit ridiculous. Spray adhesives could be better- I have a can of 3M Super 77 but it's close to the PSA in bond strength. They make weaker formulas that could be worth a try.

[Patrick Chase]

By the way, I do have some PSA 3M stuff, but after a long process of scraping it off the granite the first time, I never used it again. Is there a trick to removing the paper?

Which "PSA 3M stuff"? They make an incredible range of abrasives, with multiple varieties of PSA backing.

The 3M Stickit papers (I use the "gold" AlOx and 426U SiC) have low-tack PSA backings that are perfect for float glass and granite lapping plates. I've never had residue problems with those. The Mirka PSA papers have similarly "friendly" backings.

3M microfinishing and lapping films use higher-tack PSA backings that can leave a residue, as do Klingspor PSA papers. The trick to removing those is acetone.

Additionally, I've never heard of cleaning the paper with a magnet. It seemed like I could dull the paper very quickly with metal, which to me is normal behavior.

Note that he suggested a magnet in a paper bag :-).

[steven c newman]

All I've ever used is a very worn, 100 grit sanding belt.......by now it might be around....~ 300grit? Clamp one end down, pull the old belt flat, and then clamp the other end. Since I do wax the soles for each use, I am not really in search of a mirror-like polish that will just get scratched back up on the first swipe. As long as the plane is co-planar in the three main spots, fine to use in my shop. YMMV

[Mike Dowell]

All I've ever used is a very worn, 100 grit sanding belt.......by now it might be around....~ 300grit? Clamp one end down, pull the old belt flat, and then clamp the other end. Since I do wax the soles for each use, I am not really in search of a mirror-like polish that will just get scratched back up on the first swipe. As long as the plane is co-planar in the three main spots, fine to use in my shop. YMMV

"three main spots"?

[steven c newman]

Toe, the mouth area, and the heel.

[Jim Koepke]

Additionally, I've never heard of cleaning the paper with a magnet. It seemed like I could dull the paper very quickly with metal, which to me is normal behavior.

The magnet never touches the abrasive. It will pick up the iron particles from the abrasive sheets from 1/2" away.
The reason for wrapping the magnet in paper is so the iron filings do not stick to the magnet.

It is easy to load up the abrasive with filings, especially in the center of the plane. This can cause the plane to tilt from side to side. Then one can end up with a plane that doesn't cut evenly across its span.

jtk

[Mike Dowell]

The magnet never touches the abrasive. It will pick up the iron particles from the abrasive sheets from 1/2" away.
The reason for wrapping the magnet in paper is so the iron filings do not stick to the magnet.

It is easy to load up the abrasive with filings, especially in the center of the plane. This can cause the plane to tilt from side to side. Then one can end up with a plane that doesn't cut evenly across its span.

jtk

Excellent. So I take it you do not use any liquid on the paper, just dry? Also, how do you get the PSA paper off the granite? I went through hell to get mine off. A whole back I Was trying to sharpen chisels the scary sharp way, and so I got the granite, and some 3M PSA paper. I neatly cut out two different grit papers, and stuck them to the granite, all nice and neat, well aligned, a very good job. Once I started flattening the chisel backs, it seemed like the paper dulled really fast - like 60 seconds fast. Wonder if it was just loaded up with metal dust? Anyway, that is the point at which I took the paper off and thought to myself "I'm not going to apply, remove, and re-apply this paper every minute", and so I gave up on the whole method.

[Phil Mueller]

Mike, establishing a new primary bevel with sandpaper does often result in many paper changes (I don't own a power grinder system). I use an art supply product called spray mount. Sticky enough to hold the paper, but releases relatively easy (putty knife and solvent is sometimes needed also). In either case, it does require replacing paper often and cleaning the granite surface to apply the next sheet.

I've moved away from sandpaper for establishing a primary bevel...just too many paper changes. I do continue to use it for secondary bevel touch up (1000 grit +)...but will likely invest in some higher grit stones for the future.

When rehabbing an old plane sole, I replace paper often, and - as indicated above - just concern myself with the toe, heal, and mouth areas. I might go to 320...no need for a mirror polish IMO.