Thread: Plane sole flattening, again...

Originally Posted by D.W.

That's given as a tip for bench planes, but it makes little difference. The force of the frog is vertical and not spanning much of a plane.

It's certainly easier to lap a bench plane when it's completely together.

When I get the sole of this plane shiny enough I'll have a look with my 6" optical flat, should be interesting no matter the result.

The start of 9 micron lapping.

start of 9 micron lapping.JPG

High corner at the end of lapping

high corner 9 micron lapping.JPG

Plane mouth interferogram.

10 micron interferogram of plane mouth b.JPG

The high corner interferogram.

10 micron interferogram of high corner.JPG

With the exception of the corner the plane is flat to the limits of the Chekflat 3.

Of course at this point the flatness is well beyond the 0.00025" resolution of this gauge.


9 micron flatness gauge ahead of mouth.jpg9 micron flatness gauge behind mouth.jpg9 micron flatness gauge at heel.jpg

Rob, not sure if I understood the last two pictures, what's a interferogram?

The bright and dark lines are interference fringes. Deviations in their straightness and width indicate deviations in the surface on which they are projected assuming I'm holding the test piece normal to the anvil. The resolution of the instrument with the anvil (grating) I have is 10 microns.

Curioser and curioser.

Plane flattening study 051519a_Page_5.jpg

Now things don't get wacky until I take 8 thou at a pass. Anybody ever notice that their shavings feel a little warm? At 0.008" I could feel a little heat.

The shavings get warm, they always do. They're just usually too thin for you to be able to feel it. If you have your fingers near where the shavings are coming out, you can feel the heat. Especially in brisk smoothing or try plane work.

Not sure if the jack plane shavings get warm, they may be too massive to.

Of course, the amount of work expended must make the shavings, the plane, the surrounding air, my hands and the workpiece warmer. This is the first time I've felt them be so noticeably warm using a block plane though. I suppose that my observation is due to the fact that this is the first time I've tested a block plane in this way.

What about the data?

Am I reading the data correctly by saying that the deviation in the surface increases with shaving thickness? But until you get to a fairly thick shaving, it's pretty consistent at that sole finish?

that's what i'd expect - that coarser shavings are going to start introducing deviation when the cut quality suffers or it gets difficult to keep the plane cutting identically throughout the stroke and from one to the next.

Compare the data for the 60, 30, 15 and 9 micron testing. At 60 everything was ragged no matter the cutting depth. At 30 I could only get consistency with 0.001" cuts, pushing it maybe 0.002". At 15 I could get nice cutting at 0.003". At 9 I get consistency at 0.004" and decent work at 0.006".

Looking closer at the 9 micron data there is a trend of gradually increasing inconsistency going from 0.001" to 0.006" but at 0.008" the three sets of measurements diverge wildly.

Also notable is the fact that the planed surface is now much smoother than it was direct from the the planer (179 cuts/in.) that I used to dimension the test piece, despite the expensive Shelix cutter.

Now on to 6 micron.

I think you're isolating the effect of the sole pretty well with the data. I also think you're probably approaching (actually, you're at) the point where the sole finish is better than the rest of the plane and the limitations of size, etc, will show up due to the inability to plane thicker shavings as cleanly.

Let alone if the wood was tearout prone - you'd find that point earlier.

Nobody likes to hear me talk about the double iron so much, but one of the things i like about it is it's ultimately lower effort and it kind of buries some things like perfect sole surface finish. All of the things people do to single iron planes, you just don't need to do when the plane has a double iron (you can't have a banana sole with the mouth high, etc).

It'd be interesting to see you do this same test with two bench planes - one with a thick single iron at 50 degrees, and one with the double iron set. On my try plane, in cherry, 8 thousandths is still perfectly fine in terms of quality, but it's about the point where the plane starts to stand me still. Much more and I couldn't work through it. In actual panels using glued boards, I can't come close to that with a single iron plane because there would be tearout well before it.

Kees heiden did sort of a similar test years, ago, but not for surface quality - instead he was looking at effort expended. He put into data what I just mentioned above - that when you can control the cut quality and the surface, you'll do less work in all but the roughest of work. Not to mention, what does a good surface at 6 thousandths suggest? I know what it suggests to me - it suggests the final smoothing passes aren't going to take long because there isn't much trouble to remove.

It feeds into my "laziness leads the way" theory for someone working entirely by hand, and then what you find would help people who are working off of machines, but they're often too bullheaded to accept your suggestions because of their own egos. You may end up proving that at least in some cases, spending effort preparing the plane yields more in saved effort in use, and is a net effort reduction. My innate laziness pointed me toward controlling what the plane is doing because as I started dimensioning wood by hand with really good single iron planes, it didn't go that well, and i thought nobody would be stupid enough to work that way in the past if they had other options.

I'm planning to lap the back of the blade next. Right now it's at 60 micron and I imagine the performance will get better. After that I want to look at the blade bed and see if anything can be done there in terms of improving or modifying the degree of support.

The blade performance might get marginally better, but probably not much. If so, likely at the thinner shavings and not much at the thicker (where the wedging and bending force become more of an issue than sharpness and clearance).

Rob; food for thought.

https://paulsellers.com/2012/02/plan...e-mostly-flat/