Jointer flatness . . . did I go far enough ?

[mikey78]

Hello guys ,

I'm in the middle of an exhausting process : flattening my jointer plane (Stanley n°7 plane) ...
But . . . wait a second, before I die for the fatigue : How far should I go ?

This is my set-up :
I've a marble strip, 4 feet long, that I use with sandpaper attached for flattening.
I've checked the marble strip with my straight edge and there is no light passing in between the marble and straight edge, so I'm assuming that my trueing/lapping surface Isn't that bad
The Straight edge is a Veritas one, a 36" long and ground flat over the entire length
to within 0.0015"/0,03 mm (Sorry I'm Italian we use metric system).
I've also a feeler gauge, its smallest blade is 0,0019"/0,05mm thick,
for the purpose of this measurement I've managed to find something that is thinner than the feeler gauge blade ... I've a Borletti digital venier caliper and I've used it to measure first the smaller feeler gauge blade, when I got the 0,05 reading I kept measuring various materials untill I found
some plastic/paper sheet that was thinner than the feeler gauge blade and I've found something around 0,0007"/0.02mm and 0,0011"/0,03mm . . .
When things get smaller it's difficult to get reliable/reproducible measurements but I would say
that I defenetly found two "blades" that where increasingly smaller than the blade of the feeler gauge.

With this tools I started measuring deviation along the sole of my jointer !!!

 

[AndyT]

Find two pieces of wood, about 2m long, which you might want to glue together along their edges.
Plane them so they fit together well enough for the glue line to disappear.
If you can do that, the plane is fine.

If you can't, ask someone else more experienced to plane the wood, with your plane.
If they can do it ok, spend your time practising your planing technique.

 

[mikey78]

After couple of hours spent fiddling with feeler gauge blades ,
I came up with this result :
The Sole is quite flat, there is nowhere I can slide the 0,05 blade
in between the sole and the straight edge, but ...
... but there is a small area in the sole where there is a
barely perceptible depression/concavity :

 

[mikey78]

In the area shown above I can slide "something" under the straight edge #-o ...
As you can see from the last 3 pictures something means:
+/- 0,03 mm behind the mouth,
and +/- 0,02 mm in front of the mouth .

What does this mean in terms of flatness applied to a jointer plane ?

By the way this is my jointer . . . It has a wonderful "patina" !!!

 

[novocaine]

now do it again with the blade out and see what you get. then do it with the body supported differently, then do it with pressure on the nose then on the heal, then move the blade or skew the blade or tighten the blade. or warm the body, cool it down, use it for an hour, use it on a full moon, lick the sole etc. etc. etc.

seriously, use it, you don't need to strive for flatness unless it's all about being able to claim it.

 

[MikeG.]

What conceivable difference do you think a small concavity will make to the performance of the plane, mikey78?

 

[Phil Pascoe]

If it made the slightest difference corrugated bottomed planes wouldn't have been made.

 

[mikey78]

Ok guys hold on !!!
I'm not saying that a jointer must be "this" flat . . .
I'm just presenting to the forum members my results,
and am asking to the same members what they think about .

I know that both veritas and lie nielsen handplanes are ground flat to within 0,0015"/0,0381mm,
having said that can I also think that my jointer is close to that degree of flatness :?: ,
doesn't matter if it is necessary or not to the purposes of a woodworker.

 

[AndyT]

I still think that the best test to answer your question is to find out whether the plane will do the work required of it.

Measurements to a standard are appropriate for a manufacturer of planes. A woodworker need only be concerned about performance.

 

[Cheshirechappie]

The results of checking against a straightedge that you've posted suggest that your plane is as flat as it needs to be, and the best way to be sure is to use it for it's intended purpose. As Andy suggested above, if it'll joint two boards together closely enough for glueing, and it'll true up a board flat and out of wind, it's as flat as any jointer plane needs to be.

 

[novocaine]

ok, so you attempting to flatten it for the sake of it, that's a different story.

unfortunately you are using a sledge hammer to crack an egg.
the equipment you have is far to crude to be able to measure to the degree of accuracy you desire (don't take this the wrong way, it isn't a dig at you or anything).
this old tony on the youtube did a series on flattening a straight edge, I'd suggest you go take a look at what he did as it's pretty close the correct approach. I believe he got to within 0.001" but I haven't watched it for a while so maybe go check.

 

[mikey78]

"the equipment you have is far to crude to be able to measure to the degree of accuracy you desire (don't take this the wrong way, it isn't a dig at you or anything). "

I don't take this the wrong way at all

So novocaine, with my straight edge what degree of flatness I can reach ?
(I would say no more than 0,0015")
What is the smallest feeler gauge blade I need to use to get to that degree of flatness ?
(I would say that smaller than 0,0015" cannot be used with my straight edge)

What's your opinion ? :wink:

 

[custard]

I still think that the best test to answer your question is to find out whether the plane will do the work required of it.

Measurements to a standard are appropriate for a manufacturer of planes. A woodworker need only be concerned about performance.

I guess that's the dilemma for the new hobbyist working alone. They don't have the skill or the confidence to objectively evaluate a tool's practical performance, so all they're left with is anxious, obsessive fettling.

If the OP was in a shared workshop or a classroom things would progress much as you suggested, a practical test followed by remedial work only if necessary. But unfortunately that's not how hobbyist woodworking generally happens today.

 

[custard]

Never mind with the feeler gauges, just put a hatching across the entire sole with a thick black felt pen and keep going until it's removed. Start with a coarse grit (I use 80 grit, some use a bit coarser). Don't switch to a finer grit until the hatching is gone, the bulk of the work is done with the coarsest grit. Only then work down through the grits (I go to 240 grit, some go to 320), don't forget to ease any sharp edges and arrises along the way, finally use a metal polish which will help keep your plane slick on the workpiece.

Don't obsess about this, remember a plane will flex a surprising amount under hand pressure alone.

After that set yourself some practical training projects with a plane, like edge jointing two boards or planing a rough sawn board true and square.

An apprentice planing exercise that originated at the Barnsley Workshops and it now widely used on woodworking courses all around the world is to start with a rough sawn Oak board and make an octagonal breadboard where all dimensions are accurate to within +/- 0.5mm and the two opposite faces are flat and parallel.

If you're fairly new to woodworking you should expect this exercise to take as much as 100 hours. Besides learning about plane craft it's also a useful lesson that hand woodworking to fine tolerances is incredibly S-L-O-W!

 

[Paddy Roxburgh]

Short answer is yes, you have gone far enough, it will be fine. The slight concavity where you marked will not affect the planes performance, a convexity (a hump) could be a problem but the concavity (hollow) won't be. Novacaine's tone might be a little facetious, but he makes a good point, all metal planes, especially long ones will flex slightly in use, probably by more than your concavity.
Paddy

 

[novocaine]

Short answer is yes, you have gone far enough, it will be fine. The slight concavity where you marked will not affect the planes performance, a convexity (a hump) could be a problem but the concavity (hollow) won't be. Novacaine's tone might be a little facetious, but he makes a good point, all metal planes, especially long ones will flex slightly in use, probably by more than your concavity.
Paddy

only a little. must try harder.

as to accuracy using your straight edge. double it. then double it again for all the other errors that can creep in.

custard is correct on the method, only difference being in a machine shop you'd use prusian blue or similar instead of a highlighter.

 

[MikeG.]

.........An apprentice planing exercise that originated at the Barnsley Workshops and it now widely used on woodworking courses all around the world is to start with a rough sawn Oak board and make an octagonal breadboard where all dimensions are accurate to within +/- 0.5mm and the two opposite faces are flat and parallel.





If you're fairly new to woodworking you should expect this exercise to take as much as 100 hours. Besides learning about plane craft it's also a useful lesson that hand woodworking to fine tolerances is incredibly S-L-O-W!

Wow! That's a test. Not one that would take 100 hours, but a test. I'd spend an awful long time marking that out perfectly to start with. There's an annoying little issue with holding the workpiece, too.

 

[mikey78]

Thankyou very much guys for your advice !!!
I had the feeling that my jointer was flat enough
and you confirmed my impression 8) !!!
Now I just need to use it and see how it works :wink:

 

[AndyT]

I'll be interested to see the before and after comparison.

 

[D_W]

The only thing important on a jointer in relative terms is that you don't have the mouth above the heel and toe (as in, if nothing flexed and you placed the plane on a flat surface, the toe and heel would touch, but the mouth would not). That, and a complete lack of twist.

Even 2 thousandths of difference will be a pain in the arse trying to joint long boards. It's true that you can flex the plane, but it's also true that despite that, the plane will plane the ends off of a long joint on a flat edge, and you'll have difficulty creating a sprung joint.

You're past that. I'd use the plane as it is. It could still move more with temperature changes, etc.

I prefer a jointer that's got the toe and heel a couple of thousandths above (convex along its length) the level of the mouth. It's a bias in favor of the user. The other direction is a bias against, and with consequences (inability to actually plane a long surface flat). The favorable condition is easy to achieve. Dead flat is not, but flat within 1 1/2 thousandths isn't too difficult if you have a decent lap and are willing to spot file - the kind of thing I'd save for a presentation type plane like an infill.