Machine Surface Planing Does Perfection Exist?

[hennebury]

I'm using a precision engineers square to check a planed board for flat and square. I've laboriously set the knives in the cutter head, checked tables are parallel, etc, etc.
When using the square should there be..... no visible light..... at all, how square is square, does perfection exist?

I'm an aspiring woodworker..... not a metal working engineer.... machining tolerances.

Using the square, is very close too, good enough or does it need to be..... exactly, exactly precise?
Thanks.
Surface planing example,
The piece of timber I was checking for square I was given and checked for square when I got it and seemed preety close to that. I faced it and then edged it, repeating several times then checked.
I'm using a new Empire combination square set to measure 5.5 inches, the Empire combination square has a reputation for accuracy. I also checked using a SOBA precision tools engineering square 6 inch one, BS standard 939 grade B Accuracies less than 0.001" deviation per inch over the entire length of blade.
The board is 22 inch long x 5 inch wide. Across the face of the the board I can see a very fine slither of light towards the center of the board. I can pass a 0.1mm feeler through this gap. Towards the edges of the face no feeler gauge will fit.
Checking the edge itself, which is only about an 1/2 inch thick. Along parts of the edge, just on the right hand side of the edge, I can just about pass a 0.5mm feeler gauge but not a 1.0mm feeler gauge.
I checked the timber on the iron table of the table saw, couldn't detect any rocking movement whatsoever.
Thanks.

Its a Zen thing.

You believe that perfection is not attainable, but you must believe that it is to pursue it.

Good enough is never good enough, it is poison to the soul , it is the excuse for less than your best.

The relentless pursuit of perfection is what built all of the great things that create awe in those that see them. It is that alone that motivates us to be the best that we can be, to go further , higher, faster. The great Cathedrals, the temples, the pyramids, Taj Mahal, the things that inspire humans to be better. Take a look at the incredible Japanese joinery and handplane competitions.

Don't trust, verify.

Don't rely on measuring tools; learn to check,reference and verify. learn to understand flat, straight and square; Learn to use your eyesight and light; Learn to expand the scale, to flip to double the visible error.

Never settle. Always strive for better.

Don't let anyone tell you that it is not necessary; Nothing is necessary, but you can make it count.

https://youtu.be/eaClhzlpc_0

 

[pollys13]

If you push a piece of wood through on the left side of the thicknesser is it the same as thicknessing on the right hand side? - this would show up any error if the blades are installed quite right.
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Have you checked the fence is square when you surface it ?Yes, though it does seem to vary when checking on both ends of outfeed table. By that I mean a, really,really miniscule amount. Regarding the Oak I ran the test on, after facing I edged and checked that with square. I think face and edge are almost perfect,within tolerance.

I used a piece of Oak planed and finished by a craftsman. 58cm x 16cm I faced front and back using one pass.
A & B are both ends of board. On left side of table, A started at 19.93mm after one pass = 19.25mm B started as 19.58mm ended as 18.73mm.
Fliped timber over, positioning on right of table. A started as 19.25mm after 19.09mm
B started as 18.73mm ended as 18.04mm.