How flat????

[Anonymous]

For those of you who think plane sole flatness counts, then read on

Today I had the opportunity to place a LV bench plane on a £100,000 Coordinate measuring machine (CMM) that I have been playing with.

Ran set of measurements over the entire sole. The CMM is accurate to 0.5um (half a millionth of a meter or 1/50th of a thou)



So, how flat is the sole of this LV bench plane?

Max. deviation from dead flat was +19um - that is about 0.8 thou. across the WHOLE of the sole and min deviation was -6um across the whole of the sole :shock: :shock: :shock: :shock:

1 thou is about 25um which is the upper and lower limits of error here

Decided that I don't need to hand-lap on some wet 'n' dry :lol:

Blimey, they're good!!!!

 

[Philly]

That sounds pretty darn flat to me! :shock:
Which plane was it?
Philly :wink:

 

[Alf]

So how did the L-N do then, Tony? :wink: :lol:

Cheers, Alf

 

[Waka]

£100,000 Coordinate measuring machine (CMM) that I have been playing with.

You shouldn't have mentioned the price, now Philly will want one

Its good to see that the manufacturers claim passes the bullitin board test.

 

[Anonymous]

So how did the L-N do then, Tony? :wink: :lol:

Cheers, Alf

Only did the one plane

No point putting a L-N on there, the machine only measures down to 0.5um after all :wink: :lol:

 

[Alf]

So how did the L-N do then, Tony? :wink: :lol:

Cheers, Alf

Only did the one plane

No point putting a L-N on there, the machine only measures down to 0.5um after all :wink: :lol:

Ooo, worried it might not be as good? :lol:

Cheers, Alf

 

[Waka]

Come on Tony you can't just do one, you need to put the LN fraternity's minds at rest.

 

[Chris Knight]

Decided that I don't need to hand-lap on some wet 'n' dry

And I thought you were a precision woodworker!

Seriously, it would be very educational to check the flatness of things like float glass and granite tiles that people use to fettle their planes.

 

[MikeW]

I suspect the LN will be as good or better. But teasing is fun :lol:

The real question for me that I've never seen a study on is, how flat is flat enough? At what point does not-flat begin to affect quality of cut? Not that I feel it needs to be a scientific endeavor.

I know some of my wood planes are no where near as flat as my LN #4 1/2. But they cut better than it does. Why? I suspect it is because "flat" is only one component of all the factors which make a plane work.

Speaking of work...

 

[Anonymous]

I am about to start a 3 week holiday (from work anyway ) and will try a few items such as float glass on the machine when I return - yes even my lovely shiny LN LA Jack

 

[Philly]

Tony
Look forward to that! So you'll be spending some time in the workshop, then?? :wink:
Mike
A question I'd like answered is this-at what point does the compressability of wood take over from having a sole that is "flat enough". Lets face it-wood is not as hard as we assume it is.
Questions, questions....... :wink:
Cheers
Philly

 

[MikeW]

...Snip...
Mike
A question I'd like answered is this-at what point does the compressability of wood take over from having a sole that is "flat enough". Lets face it-wood is not as hard as we assume it is.
Questions, questions....... :wink:
Cheers, Philly

Well, sounds like a good article for the next issue (congrats by the way).

Good question. There's a thread on WC concerning Leonard Lee's statements in his sharpening book about fiber spring back and therefore the necessity of relief angles on plane blades. A related issue, really. Or maybe looking at a different effect of the same issue.

But it (wood compression) does exist, both in exerted pressure placed upon a hand plane as well as at the apex of the cutting blade: from near none on a freshly honed blade to increasing amounts as the edge fails. This one can feel by running the hand over the surface, in particular against the grain.

Too, I suspect wood variety come into play. I did slightly crease a pine board when planing it once. Blade was getting dull and I was pushing down into the cut way too much and noticed the telltale signs of small ridges at the edge of the depressions caused by plane's body. Misted it with water and set it in the sun for several minutes and it pulled back up.

So in realtion to your question, flat may well not be the complete issue some think it is. Another question maybe for Tony...does a new cast plane have any deflection uner load, so to speak? Does a jack or longer deflect more?

Well, lunch is over...Mike

 

[Anonymous]

Tony
Look forward to that! So you'll be spending some time in the workshop, then?? :wink:
Philly

Three weeks of course :roll: :lol: :lol:

Well, except for time my family demands :wink:

 

[bugbear]

Today I had the opportunity to place a LV bench plane on a £100,000 Coordinate measuring machine (CMM) that I have been playing with.

(With apologies for being obsessed)

I would VERY MUCH like to see the results of such a test on a carefully "lapped" plane, e.g. David Charlesworth #5 1/2.

I am of the strong opinion that any such plane will be convex, but I would dearly love to know HOW convex.

I also quote Roger Nixon experience with flat abrasives:

At this stage, the scratch pattern from the sanding belt was covering the whole plane sole but the surface plate was still indicating a hollow down the center of the plane...

This relates (of course) to the question of how flat does a plane need to be.

BugBear

(note to others - plane flex, and wood flex have been quite extensively discussed on OLDTOOLs in the past)

 

[David C]

Bugbear,

Yes, all my planes will be slightly convex, though the effect is more pronounced near the edges. maybe between one to two thou.

Convexity is infinitely preferable to concavity. A plane that is two thou hollow in it's length will not plane a straight edge with a one thou shaving, unless the plane is flexed, (on short components).

Almost all new planes are hollow in length, due to chucking difficulties under the surface grinder.

Relative flatness in the throat area is vital. A bump of two thou behind the throat, (distortion due to frog fixing on Bailey pattern), will prevent a one thou shaving from being taken at all.

Best wishes,

David Charlesworth

 

[Rob Lee]

(snip)

This relates (of course) to the question of how flat does a plane need to be.

BugBear

Hi -

I'd modify that question to be "how flat" AND "where" ...

If the locus of points around the mouth (fore and aft) and substantially around the perimeter of the sole are co-planar (and there's no convexity), then your plane will be able to true a surface as if it were 100% flat...

Think of a Japanese chisel....it is hollow on the back, yet the perimeter is in a single plane - and the chisel cuts true...(assuming your chisel size matches the material!)

Looking at a bench plane, you could drill 1/2" holes all over the sole, without really affecting the performance of the plane...

It's not just a question of flatness - it's a matter of how the two surfaces interact while planing - the locus of contact points is what's important.

Cheers -

Rob

 

[Anonymous]

Rob

the LV plane was dead flat within a micron or two in all important areas and only out by a few microns at either end - not bad for a 22" jointer eh? :wink: 8)