Flattening the sole of my new smoothing plane

[woodfarmer]

Although I've skimmed stuff with the lathe I think in this case I'd prefer to mill it....

.... but do you think perhaps we're going a little OTT?

probably, but I have a suitable metal working lathe here so always think in terms of lathes.. recently been sounding out trying to find a decent horizontal mill primarily for gear cutting. Although that may not be ideal for skimming

 

[Trafalgar]

Nope. You've been reading a very old post of mine on this very forum! :wink: But actually the concept is pretty obvious if one gives it a bit of thought.[/quote]

Probably parallel evolution - that page on my website is 2002, and you didn't join this forum until 2005!

But it is just a varation on classic engineering scraping practice, using coarser metal cutting tools.A real fitter
would "just" file flat, but that's a tricky skill.

BugBear[/quote]

It's no different than flattening the first face of a board -- one identifies and then methodically knocks down high spots with a shorter plane (a jack) then brings all to truth with a few final passes with a jointer. This accomplishes geometric flatness. The No. 4 (4.5 or 3) provides the surface attribute of smoothness if the jointer didn't take care of this step.

 

[bugbear]

Nope. You've been reading a very old post of mine on this very forum! :wink: But actually the concept is pretty obvious if one gives it a bit of thought.

Probably parallel evolution - that page on my website is 2002, and you didn't join this forum until 2005!

But it is just a varation on classic engineering scraping practice, using coarser metal cutting tools.A real fitter
would "just" file flat, but that's a tricky skill.

BugBear

It's no different than flattening the first face of a board -- one identifies and then methodically knocks down high spots with a shorter plane (a jack) then brings all to truth with a few final passes with a jointer.

No it's not; flattening wood with hand techniques doesn't involve a flat reference surface, the action of a plane is quite different, since it will/can ONLY take off high spots, and carries its own reference surface (ironically, the flat sole the OP is trying to create).

The techniques Mignal and I recommend uses tools that are quite capable (if not guided coorrectly) of making low spots lower.

BugBear

 

[Trafalgar]

The point, quite simply, is to find the high spots and reduce them to the lowest low spot on the surface all the while not throwing the surface into twist or some other defect that wasn't present before. It's not easy per se, but it's not rocket science either.

It takes more common sense than anything.

The easiest way to screw it up is assuming if one has a flat reference surface like a granite plate that it is impossible to make the sole of the plane worse.

Find high spot, sand high spot, rinse, repeat, and watch for twist.

If you think a plane can only take off high spots you must have never planed a board longer than your longest plane.

 

[Jacob]

....

If you think a plane can only take off high spots you must have never planed a board longer than your longest plane.

Yep. Wood is bendy. Planes probably are too.
Even if the plane is perfectly flat and the wood perfectly rigid, the protruding blade can cut a hollow (cf. "sagitta" and geometry of a circle). You can also do the opposite if you want to (round the surface from end to end). In fact that is what often happens if you don't pay attention.
Planing is a series of controlled scoops - flatness is achieved as near as possible by eyeballing the results and altering the technique accordingly - you can't rely on the plane to do it for you.
It follows that a slightly convex sole is probably quite OK but concave probably not.

 

[JohnCee]

You can get the back and sides surface ground to British Standard flatness for £25.
Can't understand why anyone would want to undertake this messy, time wasting job by hand.

 

[bugbear]

If you think a plane can only take off high spots you must have never planed a board longer than your longest plane.

It's all relative Charles - if there's a local 1" deep dent in a board, how much surrounding wood would you HAVE to remove
to plane it out? Now compare that answer with removing a 1" high bump.

Planes remove high spots, at least to a good working approximation in the real world. It's why we use them,

BugBear

 

[Trafalgar]

A plane, alone, is not sufficient to impart geometric flatness to a workpiece. Witness the use of winding sticks and straightedges in just about any reputable British woodworking manual you can name and in practical use too of course.

As for local bumps, it depends. Even a relatively long plane can ride up and over a bump/hump depending on how it's wielded and the size of the imperfection.

I tend to work really big bumps down with a short plane first; a long plane can teeter-totter on a big bump. This is essentially scrubbing though it may not take place with a scrubbing plane, per se. I happily whip out a Surform on really nasty boards. Nothing takes down high spots faster and more reliably. You can get right on top of a bump and take it down in a few strokes.

It is also not true that a board can only be made as flat as one's flattest hand plane. A board can be made as flat as one's most accurate straightedge. To do so you actually end up finishing the process with progressively SHORTER planes (down to local scraping if necessary) rather than long ones, all in a process of very fine tweaking in order to mirror the straightedge's accuracy to the surface. Anybody under the impression that they can only get a board as flat as the sole of their No. 7 is mistaken. This is obviously rarely if ever necessary but I think it's important to understand where the theoretical bounds lie.