Machine Surface Planing Does Perfection Exist?

[pollys13]

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.

 

[Lazurus]

Sounds a lot of effort to me, is the board "perfect" enough for the job intended, wood moves anyways so will "perfection" last even if achieved?????

 

[powertools]

My advice would be don't try to bring presision metal working methods into your woodworking you will never be happy with the results.

 

[MattRoberts]

As Lazurus says, any perfection that you achieve would only be temporary due to wood movement anyway.

I feel that accuracy visible to the eye is sufficient - to me, that equates to anything under 0.5mm accuracy, be it a joint or the squareness in your examples

 

[Bigdanny]

Probably Marunaka. If you have the money for a machine it should give you near as damhikt perfection.

 

[sunnybob]

You do know that construction industry standard for wood work is plus or minus a quarter inch?

cabinetry needs a lot more precision, but I think you really are trying too hard.

 

[ColeyS1]

Just put a square on some timber I planed up on Monday.

If at first you don't succeed...order in more timber lol !
If there's no wobble (twist) it's either the fence isn't square or you're not pushing the wood in tight to it.

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[pollys13]

OK thanks, close enough, should be good enough.

 

[ColeyS1]

Have you checked the fence is square when you surface it ?

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[pollys13]

Yep.

 

[ColeyS1]

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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[Cordy]

I use a digital level box to check infeed and outfeed; longitude and latitude

On the fence too
Results are satisfactory

 

[johnnyb]

There's definitely right and wrong. Ie I would never expect a piece of par to be true and four square. I think bits of cup and slightly out of square are less troublesome than long slow bends and out of wind problems.
But I would expect something I'd planed and thicknessed to start and stay reasonably four square.
If it wasn't id suspect your technique or the capabilities of the machine.

 

[Distinterior]

I use the same digital level as Cordy on my Hammer P/T. Its useful for checking & adjusting all manner of machines including table saws, mitre saws, bandsaws and radial arm saws.

 

[Doug71]

I wouldn't worry too much because you can take your nice square, straight piece of 4x3 redwood (for example), cut a large rebate out of it for say a door or window frame and if you don't use it straight away after a few days it has taken on a whole different shape, cupped and twisted beyond recognition (speaking from recent experience). #-o

 

[pollys13]

Coley.
I'll see and let you know and thanks everyone else for input.

 

[ColeyS1]

Coley.
I'll see and let you know and thanks everyone else for input.

Sounds like a plan ! If one side thicknesses at 21.5mm and the other at 20.5mm then that'd explain why even having the fence square to the bed produces an out of square piece of timber. If both sides read the same, the blades are installed correctly and it must have something to do with the fence.

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[pollys13]

OK cheers Coley As I say I'll check it out and get back to you, away Sat/Sun so probably Monday.

 

[rafezetter]

Just put a square on some timber I planed up on Monday.
If at first you don't succeed...order in more timber lol !
If there's no wobble (twist) it's either the fence isn't square or you're not pushing the wood in tight to it.

Now show me the certification that that square is square

OP I fell down that hole myself - but learned that what everyone else is saying is true - if YOU think it's good enough, the customer absolutely will not see it, assuming ofc you don't have an inherantly sloppy "that'll do" mentality which it doesn't seem like you do.

Wood moves, but hardwood is easier to get to tight tolerances when dimensioning - if it moves a tiny bit after that and doesn't affect the project or joints, it REALLY doesn't matter.

 

[custard]

As well as using metal straight edges I make up a few wooden straight edges in different lengths. They're lighter to use plus they're less vulnerable when for example you're checking a glue-up and don't want water or glue all over your precious metal straight edge.

They only last a few years, but I've never had one fail because it's warped, after a while they get dented on the reference edge and after repeated planings become too thin and whippy.

Here's one that's a year or more old now, and it gets used almost every day. When tested against a high quality metal straight edge it's still as true as when it was first made.

Here's the secret. It's all about the wood.

I make these from quarter sawn Cuban or Brazilian Mahogany with arrow straight grain. Furthermore it's timber that I know has been dried properly, and I take it down to final dimensions in small steps over several days. It's pretty much the same methodical approach I use to make piston fit drawer sides, or any other component where dimensional stability is critical.

The right timber allows almost engineering levels of precision. The vast majority of timber, and certainly any timber you'd get from your local DIY shed, probably won't.