Flattening the sole of a cast steel hand plane?

[John C Cox]

Please do the wobble test that Stephen mentions and check it with a flat 0.002" feeler gage on a surface plate (or a clean fresh sheet of notebook paper) before you ever lap it.... I just checked a brand new Stanley block plane on my surface plate - it's better than 0.002" everywhere I could check... There is no need to lap it - and you are likely to cause more problems than you will solve.... (The iron is a different story - but that's not what this thread is about. )

It is useful to lightly "stone" the bottom of a plane with a good flat fine sharpening stone in a figure 8 pattern to knock down burrs that arise before they track up your work...

Be careful about sanding before checking. I have run into quite a few issues with PSA backed sandpaper where it rides up proud a bit on the edges... And can leave you a bit convex... You are better off using wider sheets glued down - and stay away from the edges... Check your progress often against a ground straight edge or surface plate with feeler gages.... Just because an area is not ground by sandpaper doesn't mean it's not flat.. And just because an area is ground by sandpaper doesn't mean it is....

[Jim Koepke]

OK, I'm kind of intrigued and baffled by all this sole flattening.

I'm intrigued, because the level of accuracy people are striving for seems to be far greater than anything needed in normal woodworking. I could see maybe having one or two smoothers capable of shaving a couple thou in thickness as a final pass, but a jack plane or jointer? no way, those planes are for taking off material quick. You don't need to have a sole flat to 0.003 to do that. The whole measuring your shaving with a micrometer thing seems like it started around the time of the internet. . . . .

I'm baffled, because when I read threads and see videos and articles on sole flattening, people are typically using things to both measure and flatten (plain steel or aluminum rules, granite tile from Home Depot, glass on a workbench, table saw wings) that are not nearly as accurate as the accuracy that they are striving for. Not to mention not close to being rigid enough to maintain that flatness with someone pushing a plane across them. To accurately measure a plane sole to a couple thousands, you need an actual surface plate or machinists straight edge, and machinists tools. When you look at lists of woodworkers tools of yore, you don't see surface plates, feeler gauges, 1-2-3 blocks, micrometers, or lapping compound. Why is it that they are suddenly needed now?

So I am truly curious, how flat do folks think their planes need to be (and why)?


And now I am ducking before people start hurling their LA jack planes, high frog smoothers, bronze bodied planes, and thick irons at me

You are correct Andrew. In most normal woodworking taking a shaving less than a thousandth of an inch has little or no advantage. In many cases taking a light shaving can help mitigate tear out.

It is always nice to have one good smoother in the kit. For anything else, it really only needs to work without problems. That is why my suggestion is to always use the plane first before lapping the sole. Don't do the work just because someone, like me, did it on Youtube.

If one is careful and pays attention to what they are doing, one can get to a very flat sole without special equipment. It wouldn't surprise me to learn woodworkers of yore had their ways of ensuring their tools worked as well as their hands. If they could smooth the top of a piece of cabinetry, they surely could smooth the bottom of a plane.

jtk

[Andrew Seemann]

Sometimes I wonder if the improvement from "sole flattening" is actually just from polishing the sole, taking off the rust from an old plane or gunk & oxidation that may have accumulated on a regularly used plane. That would definitely improve performance.

Don't get me wrong, when I tune up a new-to-me plane, I check to see how flat it is by setting it on a reference surface flat enough for woodworking, usually my cast iron table saw and make sure it doesn't rock or have a bow. If it passes that test, I then rub it on my stationary belt sander (not running) to see if it has a relatively even scratch pattern and if it does, that's it for flatness. If it doesn't, I'll flatten it until it is good enough (which has been rarely needed for most planes). I clean off the rust on the sole, wax it up, and I'm done with the bottom.

If I did run into a plane not flat enough for normal use with minor work, chances are I would put it on the shelf for parts, or just use it as a beater.

[Warren Lake]

wanting to look at this a bit more did another test with three number five planes. First on 3M 220 grit. Im on a shaper table and its flat. I did a number of swipes on the planes then checked the outside edge of the paper and its flat. no issues with the paper edges being up. I think this is more accurate than some sort of adhesive spray application could be inconsistent. The paper itself measures accurate bang on where ever I measured it.

Put my lines on again and put 150 grit on and did one forward pass one on each then turned them end for end and continued on so as the paper wore this would be the most even way to do it rather than one plane at a time. The three planes are number one two and three from the bottom up.

1 is the one with heavy wear long life, 2 had very little use on it, 3 is another one that was used a lot but not as much as 1. They were all different and 2 which was hardly used is clearly not flat as it came which shows at least with that brand you cannot count on the bottom being flat. Its a record the other two are Stanley bailey ones.

I dont know what flatness is needed and they all work well enough. Lots of stuff in a shop is different levels of accurate and it all still works well enough. Originally when I did this I had two sheets side by side so could do an x pattern like body work, that worked well as you could use scratches as a guide coat as well.

Capture.jpg

[Lasse Hilbrandt]

I have a friend who has a milling machine. Would that work ?

[Peter Christensen]

I have a friend who has a milling machine. Would that work ?

If the machine is big enough to hold the plane and your friend knows what he is doing, it will do nicely. You may still need to sand the sole a little to smooth it. A surface grinder is the best choice with the mill a close second.

[Mark Rainey]

Bought a used Stanley jack plane 18 years ago for $30. Just getting started I used it for everything. Decided to flatten the sole & brought it to a machinist. His estimate $20. He called me when it was done & said he put a lot more work into it than he thought it would take & said he had to charge me $50 and still he lost time on the job. And that was 18 years ago.

[Warren Lake]

Plane 2 the middle one is out .0015 on the heel on all those magic marker lines that is how much its out of true. Thats the one that is hardly used so how it came. the bottom and top one seem to be pretty consistent down the middle likely lapped from years of just being used. will have to continue down to see. I wasnt on this to flatten them but to explore some of the info here and get a reading off them.

[John C Cox]

Bought a used Stanley jack plane 18 years ago for $30. Just getting started I used it for everything. Decided to flatten the sole & brought it to a machinist. His estimate $20. He called me when it was done & said he put a lot more work into it than he thought it would take & said he had to charge me $50 and still he lost time on the job. And that was 18 years ago.

That's likely because it took a lot of time for him to figure out how to make jigs/fixtures to hold it flat on his surface grinder... Not because the grinding presented any difficulties... The inside of a plane sole is not really a friendly shape for a surface grinder bed... The manufacturers have specially designed nests that precisely fixture the sole for grinding... These cost many thousands of dollars to make - but it's price is paid back over tens of thousands of units...

[Mark Rainey]

Good information John

[Marinus Loewensteijn]

OK, I'm kind of intrigued and baffled by all this sole flattening.

I'm intrigued, because the level of accuracy people are striving for seems to be far greater than anything needed in normal woodworking. I could see maybe having one or two smoothers capable of shaving a couple thou in thickness as a final pass, but a jack plane or jointer? no way, those planes are for taking off material quick. You don't need to have a sole flat to 0.003 to do that. The whole measuring your shaving with a micrometer thing seems like it started around the time of the internet. . . . .

I'm baffled, because when I read threads and see videos and articles on sole flattening, people are typically using things to both measure and flatten (plain steel or aluminum rules, granite tile from Home Depot, glass on a workbench, table saw wings) that are not nearly as accurate as the accuracy that they are striving for. Not to mention not close to being rigid enough to maintain that flatness with someone pushing a plane across them. To accurately measure a plane sole to a couple thousands, you need an actual surface plate or machinists straight edge, and machinists tools. When you look at lists of woodworkers tools of yore, you don't see surface plates, feeler gauges, 1-2-3 blocks, micrometers, or lapping compound. Why is it that they are suddenly needed now?

So I am truly curious, how flat do folks think their planes need to be (and why)?


And now I am ducking before people start hurling their LA jack planes, high frog smoothers, bronze bodied planes, and thick irons at me

Just compiled a long reply and it disappeared so I'll try again.

I am with Andrew on this for a real need of flattening the sole. The plane itself will twist and change shape when we put pressure on it, not to mention that wood itself is rather flexible and will compress locally when we go over it. Just a long strip of wood will flex in all directions and on a microlevel at the length of a plane it will also change shape.

If I was to flatten a sole I would get a flat steel plate (or a cast iron one) and use the grinding paste that is used in the automotive industry for seating valves. Failing that I would clamp the plane upside down and use a coarse waterstone. I would not use sandpaper as the backing is soft and it will compress and do other things that you do not want. (I ground telescope mirrors over 40 years ago - that is a whole science on its own). The waterstone is a good solution when you have hit a nail and there are some nicks that are protruding.

I suspect that the interest in flattening of soles, bevel up planes , thicker irons, other steels etc all can find their origin in that the knowledge of the old timers no longer is being passed along and that the younger generation is experiencing problems with tearing out, chatter etc. The manufacturers will quickly tell them that they are in need of something better than their "old" bevel down planes and sell them thicker blades, different steel and if that does not work well then you need a bevel up plane and untold different blades all with a bevel ground to a different angle. And your sharpening has not been good enough, you'll need all these diamond and waterstones to the 30000 grit and a translucent Arkansas stone is mandatory too, your workbench is not solid enough, get maple workbench that weighs 2 tonnes and the list goes on.

It was only recently that I found out how to set the chip breaker correctly and I wish I had known this over 40 years ago when I had problems with tear out in mahogany while building boats. No old timer around at that time to teach me properly. For smoothing the chipbreaker needs to be set very closely to the end of the plane iron - any closer and the chip breaker would be acting as the plane iron. Head over to 'wood central' and check out the article on 'setting a cap iron'.

I tried this on some maple that 6 years ago I had problems with. I bought a bevel up jack plane for solving this problem and it did not, grr..... Tightened the mouth, added some blades, ground those blades to the recommendations (15000 grit) and it was still happpening. After reading the recommendation I pulled out my #3, set the chipbreaker as close as I could and.... problem solved! Not to mentioned that the iron on the #3 had been sharpened to #2000, not even a mirror finish. Who knew.

[Jim Koepke]

[edited for brevity]
I am with Andrew on this for a real need of flattening the sole. The plane itself will twist and change shape when we put pressure on it, not to mention that wood itself is rather flexible and will compress locally when we go over it. Just a long strip of wood will flex in all directions and on a microlevel at the length of a plane it will also change shape.

If I was to flatten a sole I would get a flat steel plate (or a cast iron one) and use the grinding paste that is used in the automotive industry for seating valves. Failing that I would clamp the plane upside down and use a coarse waterstone. I would not use sandpaper as the backing is soft and it will compress and do other things that you do not want. (I ground telescope mirrors over 40 years ago - that is a whole science on its own). The waterstone is a good solution when you have hit a nail and there are some nicks that are protruding.

Marinus, you and Andrew are in agreement with a point of mine also presented earlier in this thread. There is no reason to abrade the sole of a plane without evidence of a problem.

My set up does not have any way for me to truly test the flatness of a plane sole other than by eye and result. My tendency is to ignore the eye if the result is sufficient for a particular plane's function.

A jointer doesn't need to make a 0.001" shaving. A jointer does need to be able to take a shaving consistently without pulling in to or out of a cut.

One goal of tuning up any plane is to give a user's hands control of their work instead of its shortcomings controlling how one performs their craft.

jtk

[Allen Read]

....My advice on plane soles is to only lap them if it is really needed, as many times it isn't needed.

If a plane can take a shaving without problems, the sole likely doesn't need to be lapped.

This is the most important consideration.

Second is the thickness of the granite. If it's 2 cm or less, it may be too flexible for flattening. I'm in the stone trade and it's hard for most to understand that thin granite is a bit flexible. Not much, of course, but enough to cause problems with plane sole flattening. You can support it or use a thicker piece of granite. I've found that 3 cm is usually stiff enough, but even this has to be supported.

When flattening, change your grip on the plane every so often. We all have tendencies to apply pressure unevenly so that you can easily sand too much in some spots and not enough in others.

Good luck,
Allen

[Tom Trees]

If lapping a plane, stay away from the edges so the marker ink remains.
If you don't, and lap on a dead flat plate with taut sandpaper, it will create a convex surface.
This will happen no matter how meticulous you are with cleaning the abrasive and repositioning of the plane.
You only use a full width and length abrasive on the final few strokes eliminating your inked edges.
I use a strip of self stick sandpaper and lay my cut strips on top.
I get a pair of abrasive strips from a regular roll of sandpaper, and cut it less than the planes length I'm working on.
It will stay put because 100% of the abrasive is in contact with the plane

Don't trust anyone who doesn't get the feelers out and demonstrate that the sole is flat!
No-one on youtube has demonstrated how to lap a plane to get an acceptable result of a flat surface.

Just remember what I said about creating convex surface, so you realise it before its way out, if you don't believe me.

Tom

[Stewie Simpson]

OK, I'm kind of intrigued and baffled by all this sole flattening.

I'm intrigued, because the level of accuracy people are striving for seems to be far greater than anything needed in normal woodworking. I could see maybe having one or two smoothers capable of shaving a couple thou in thickness as a final pass, but a jack plane or jointer? no way, those planes are for taking off material quick. You don't need to have a sole flat to 0.003 to do that. The whole measuring your shaving with a micrometer thing seems like it started around the time of the internet. . . . .

I'm baffled, because when I read threads and see videos and articles on sole flattening, people are typically using things to both measure and flatten (plain steel or aluminum rules, granite tile from Home Depot, glass on a workbench, table saw wings) that are not nearly as accurate as the accuracy that they are striving for. Not to mention not close to being rigid enough to maintain that flatness with someone pushing a plane across them. To accurately measure a plane sole to a couple thousands, you need an actual surface plate or machinists straight edge, and machinists tools. When you look at lists of woodworkers tools of yore, you don't see surface plates, feeler gauges, 1-2-3 blocks, micrometers, or lapping compound. Why is it that they are suddenly needed now?

So I am truly curious, how flat do folks think their planes need to be (and why)?


And now I am ducking before people start hurling their LA jack planes, high frog smoothers, bronze bodied planes, and thick irons at me

Andrew; you may find the following article of interest; https://www.kinexmeasuring.com/downl...oodworkers.pdf

regards Stewie;