Metal plane sole surfaces finishes.

[Cheshirechappie]

Some months ago, I purchased a new, cheap Bailey-style Number 3 size plane. The sole wasn't flat - no way would it take a fine shaving, so this afternoon I set to with a jury-rigged surface plate, some Engineer's Blue, and a couple of files (8" second cut three-square and 6" smooth three-square) to get it a bit flatter. The process turned out to be quite quick (smear thin film of blue on surface plate, apply plane sole and rub once, lift off and file away the marked bits - the curved faces of the three-square file means you can get at spots in the middle of the sole if you have to) but resulted in a sole that, whilst flat and reasonably smooth, was not polished.

In order to check if a better shaving resulted, I reassembled the plane and tested it. Much better - thin shavings could be produced.

Not being satisfied with the surface finish, I then treated it to a good rubbing with 120, 240 and 400 grit wet-and-dry; the sole went from file-surface smooth to polished smooth. Just to see that all was well, I put the blade back in and tried it again.

To my surprise, the plane cut much better, producing even thinner shavings, and giving a more lustrous finish to the wood. The blade was not resharpened between tests, and the cap-iron remained undisturbed, so there was no influence on results from either. Unsurprisingly, there was far less sole friction, too.

The conclusion is therefore that a smoother finish to a plane sole can help to produce a better surface finish on the wood. It is true that the original filed finish was somewhat rougher than any plane sole would usually be, but the difference in performance between filed and papered finishes on the sole was quite startling.

If anybody has a 1980s or later plane with a sole finished on a linisher, it might be worth a bit of work with some wet-and-dry wrapped round a nice flat block of wood. Polishing the sole might improve the plane's performance noticably.

 

[AndyT]

That's interesting and a bit surprising.
I always scribble on the sole of a metal plane with a bit of candle and find it makes it much easier to push and control. Did you do this on your plane at all?
I'm wondering if the difference is due to the improved speed and smoothness of the forward motion of the polished plane, rather than any effect from the smoothness of the plane itself.

 

[Cheshirechappie]

I did apply a bit of beeswax to the polished sole, but not until after testing without. The wax did improve sole friction quite a bit, but had no effect on quality of cut or finish on the workpiece.

The full sequence was thus:

Plane as bought - thick shaving, rough finish, very poor performance.

Plane sole filed flat, no wax - thinnish shaving, decent finish to workpiece, noticable friction between sole and workpiece.

Plane sole polished with wet-and-dry, no wax - thinner shaving, better finish to workpiece, less friction between sole and workpiece.

Plane sole polished with wet-and-dry, waxed - same thinner shaving, same better finish, much less friction between sole and workpiece.

I rather doubt that the wet-and-dry took off enough metal to modify the sole flatness. I didn't use very coarse grades, and only did enough work to take out the worst of the file scratches and improve surface slickness. I didn't spend long on it. My memories of long ago lapping plane soles on emery fixed to glass are that it takes a long time to shift much metal, even with 60 grit; I didn't do nearly enough work with the abrasives this time to affect flatness.

 

[n0legs]

Great minds and all that CC =D>

Some might remember Wizard giving me a sole and frog a little while back. It's a corrugated sole and over the last few months I've been building it up, I'll do a separate thread on it soon as it's finished.
Anyway this weekend I got down to sorting the sole out, Wizard did say it was flat and fairplay it is.
It didn't need a lot but I got up to 1200 grit and then decided to polish it up with some Farecla G3.
I don't know if it's due too having a corrugated sole or the fact it's polished, but by eck she flies. The blades quite sharp, which helps, but she cuts so well. I'm thinking of giving all my planes this treatment.

If you will indulge me, a few pics.

 

[MIGNAL]

Yes, even 120G struggles to remove much metal on a Planes sole. Visually 180G seems to give the sole a fairly decent finish. Maybe if you used the abrasive in any random direction it would probably appear much worse.
I'm struggling to think why a finer grit would lead to a thinner shaving.
I have a No. 4 that has been finished to 180G. I think I measured a shaving at 0.04 mm's in brittle bubinga (may have been another wood, it was a while ago). I'll take it to 400G and see if it goes a little finer.

 

[sdjp]

I'm struggling to think why a finer grit would lead to a thinner shaving.

Indeed, that's a very interesting question. Here's my best theory:

Firstly, I observe that the planes sole mostly rides on the smoother surface. (Also, taking more than one pass is common. Therefore if the initial wood surface roughness makes a difference, that'll iterate out).

Secondly, the two mating surfaces are both flat, and therefore a matching pair. Thus, as the surface gets smoother there is more contact between the planes sole and the work piece.

Of course, under sufficient magnification, we can see the smooth is 'nearly smooth'. Strictly, we can talk about the level of 'surface roughness' - where a smoother surface has a lower surface roughness. I'll skip try to define this formally. (And the flat is 'nearly flat', but I don't think that is so crucial here).

Final observation is that the thinnest plane shavings have a thickness corresponding to the finer grits: I believe the record thinnest shaving (from those wacky Japanese, unsurprisingly), is 3 microns. Thats about the size of P8000 or so grit. A 'typical' shaving is 250 microns, which is about P70 or so grit; hence we can assume that the finest shaving from a smoothing plane is somewhere between the two.


If we consider what happens when two flat surfaces of similar surface roughnesses pass over each other, taking the lower one to be a fixed reference, then we can see that the upper surface will rumble about, to a degree 'commensurate' to the surface roughness. Assuming the plane blade is infinitely rigidly attached to the sole, then that means that the blade will move by the same amount.

Should the cutting depth fall to 0, then blade stops cutting, at least for a small part of the stroke, and this stops the planing action. Therefore, the smoothness of the plane sole forms an _lower bound_ on the shaving thickness.

To quantify (as best I can without breaking out the silly maths): The surface roughness is, roughly, half the grit size [0]. The top surface moving will experience a deflection of scale around the geometric mean of the two roughnesses - in this case, that's the surface roughness. The plane stops cutting when the maximum of the motion is equal to the shaving thickness.

Therefore, assuming an infinitely sharp blade in an infinitely rigid plane, the limit to shaving thickness for cutting an isotropic material is about half the grit size that the sole was lapped to.

For the one data point: p180 grit is around 80 microns, hence suggesting a 40 micron (0.04 mm) shaving limit. (I wrote all the above before calculating that, honest!). Which is a pretty good outcome for such a back of envelope model [1].

Of course, the surface roughness will be improved by waxing; and looking at the records, there's no point going for 3 micron or better (unless you are actually truing for a world record), which suggest that the finest it's worth lapping the sole to would be about 2000 grit (giving a ~5 micron limit. Even that's excessive, for everyday use).

At P360, this model gives a 20 micron shaving limit; which seems to me to be a good guide as to where to stop. There's so many other factors (blade sharpness; anisotropic material etc), that getting a 20 micron shaving strikes me as pretty damn thin; trying for thinner is going to run into other problems. P400 is probably easier to find, and not much different (18 micron shaving limit). At some point, you'll get other factors dominating the surface roughness (natural roughness of the cast iron; oxidation etc), which would also give a limit.


I have a _really_ cheap and nasty No4 (Clarke). It's so bad, I have swithered about upgrading it to a Silverline or Faithful; or just biting the bullet and getting on with the fettling. At this point, the sole is so unflat (and unsquare), if it were a woodie I'd be starting with an axe! Once I get it flatter, I'll experiment with the lapping the sole, see if I can get it to match predictions of the model. That's likely to be a summer project, however.


[0] I think it's about half for a fixed grit (stone/paper), depending on the grain geometry, and a different fraction for loose grit, more dependant on grain geometry. Perfectly spherical grains will cut when fixed, but not when loose, for example…

[1] Or, to give them the 'proper' physicist name: Spherical cow models.

 

[David C]

I have polished plane soles for many many years. The reason being less friction, so easier to push. Wax rarely used except for sticky timbers.

We do this all the time on my "Tool Tuning Course".

We go to blunt 240 grit wet & dry when flattening or checking.

This is then polished with 0000 wire wool and Autosol.

The finest shavings we get are 0.0005 inch or even slightly less. This is around twelve microns which sounds more impressive !!

David Charlesworth

 

[sdjp]

This is then polished with 0000 wire wool and Autosol.

The finest shavings we get are 0.0005 inch or even slightly less. This is around twelve microns which sounds more impressive !!

Difficult to judge the surface roughness there; as it depends on the duration and exact manner of the buffing process. However, 0000 wire wool has a fibre width of around 25 microns typically … Granted, the surface wire wool leaves is different from sand paper; and the autosol will make some difference, but if that shaving thickness was limited by the sole surface roughness [0], then that's bang on what the model points to. Or is total coincidence, of course - can't rule that out.

[0] Although, that fine a shaving I'm thinking other factors are also in play too...

 

[MIGNAL]

What type of wood? I suspect it's difficult to obtain these fine shavings on a brittle open pored wood compared to a very close grained relatively soft hardwood.
There's a reason why those Japanese planing competitions use a type of Cypress.

 

[David C]

I have heard that the Japanese use a special wood for their competitions.

Mine is Sycamore.

David

 

[Bod]

That's interesting and a bit surprising.
I always scribble on the sole of a metal plane with a bit of candle and find it makes it much easier to push and control. Did you do this on your plane at all?
I'm wondering if the difference is due to the improved speed and smoothness of the forward motion of the polished plane, rather than any effect from the smoothness of the plane itself.

+1
The candle wax once spread, keeps rust at bay.
Its cheap, easy to apply/reapply.
Works on saws as well.

Bod

 

[Cheshirechappie]

What type of wood? I suspect it's difficult to obtain these fine shavings on a brittle open pored wood compared to a very close grained relatively soft hardwood.
There's a reason why those Japanese planing competitions use a type of Cypress.

I used two test-pieces, a nice straight-grained piece of redwood (Scot's pine), and a rather nasty, hard, knotty, interlocked piece of oak. You're quite right that not much could be drawn by way of conclusions from the oak shavings, because they just broke up. but the finished surface did feel slightly nicer with the polished sole. The pine was much more revealing, since definite shavings were made, and the finished surface went from acceptable with the filed sole to lustrous and gleaming with the polished sole.

 

[Cheshirechappie]

I have polished plane soles for many many years. The reason being less friction, so easier to push. Wax rarely used except for sticky timbers.

We do this all the time on my "Tool Tuning Course".

We go to blunt 240 grit wet & dry when flattening or checking.

This is then polished with 0000 wire wool and Autosol.

The finest shavings we get are 0.0005 inch or even slightly less. This is around twelve microns which sounds more impressive !!

David Charlesworth

I suspect the Law of Diminishing Returns applies here. There was a very noticable difference between filed and paper-polished finishes, both in friction, shaving thickness and finished wood surface. The wax did diminish friction a bit, but made no difference otherwise.

I rather suspect that taking a plane with a decent sole finish and polishing it would not affect it's performance significantly; the sole has to be fairly rough (filed, linished, badly scratched) for polishing to improve it to any noticable degree.

 

[Cheshirechappie]

Secondly, the two mating surfaces are both flat, and therefore a matching pair. Thus, as the surface gets smoother there is more contact between the planes sole and the work piece.

I think you're on to something, there. When it's surface is rough, the plane will to a great degree skate over the peaks of metal on it's surface; when those peaks are papered off, the plane's sole will be (very slightly) lower to the work, and that will reflect in what the cutting iron will do.
That will reflect in the friction, too - the peaks on the rough sole will drag more on the wood's surface than will the more polished one.

 

[Phil Pascoe]

Assuming a reasonable finish, the sole surely can't have that much influence, surely, or a solid sole would perform better than a corrugated one?

 

[MIGNAL]

Well, that was a good hour of my life wasted. I went from 180G to 240, 320, 400, 600 then to 800, 1,000, 1200, 1500, finally 2,000G.
I then followed it with Autosol. Then non doped plain Leather, followed by the final supreme polishing on the thighs of a hundred Cuban virgins (that was hard work).
I can now take a shaving of 0.001" instead of 0.0015". Not even those Cuban virgins could help me beat David C.

 

[Racers]

Just squeeze the shavings harder in the micrometer until you get to the required thickness :wink:

Pete

 

[Cheshirechappie]

Assuming a reasonable finish, the sole surely can't have that much influence, surely, or a solid sole would perform better than a corrugated one?

I think you're quite right if the sole finish is reasonable - or at least what most of us would regard as reasonable. The filed (smooth file) finish was rather rougher than I would regard as reasonable, but about comparable with one or two 'new' linished plane soles I've been unfortunate enough to encounter. Giving them a bit of a polish would improve things (assuming acceptable flatness, which can't be taken for granted on any plane a manufacturer has seen fit to send out with a linished finish).

 

[David C]

I do not wish to mislead. My shavings are not full width and 12 feet long.

However, with good sharpening and a slightly cambered blade, it should not be difficult to get 1/2 thou shavings off a Sycamore edge.

We use this as a test for flatness in the vicinity of the throat.

best wishes,
David

 

[whiskywill]

a hundred Cuban virgins (that was hard work).

Finding them or stropping them?