No 7 Jointer - How flat is flat?

[Graham Orm]

I'm still not comfy with the idea. Whilst it cuts down on lapping, and probably friction whilst planing, there will be a period on every stroke where the blade will cut deeper until the un-filed rear of the sole reaches the work, then it will lift the blade a couple of thou and you will get a ridge forming.....surely?

It works. I use the method on the English wooden planes that I have - two hollows along the length of the Plane. In the correct places. Of course I can just use a Cabinet scraper rather than a file.

Along the length maybe, but the image shows the metal removed across the width.

 

[MIGNAL]

Yes, right across the width. A scalloped area (roughly) starting 1/2" from the front edge of the Plane (toe) to 1/2" in front of the blade. Same kind of thing in the area behind the mouth to the heel of the Plane. Like a child's drawing of the wavy sea.
3 (or 4) points of contact along the full length of the plane but all aligned (coplanar?).

 

[Corneel]

That's also how Japanese planes are prepared, also their jointers.

I think it works kind of like this: When flattening, use a plane appropriate to the length of wood. You press down on the front until the plane is mostly on the surface, then you start to move your pressure to the back. I don't think you will be able to detect a ridge if you happen to drop down the plane a bit too early, the further the plane is on the wood, the less the effect. This smoothes out any uneveness during the cut.

 

[Sheffield Tony]

According to school physics, friction doesn't depend on surface area, just the force and surface properties. Sort of figures because reducing the contact area increases the pressure on the remaining surface. SO ... what were corrugated soles all about ?

I suspect school physics is ... incomplete. I note that formula 1 cars have tyres whose size and lack of tread appears
explicitly designed to maximise contact area.

I'm sure you are right, school physics (or indeed any physics) is only "true" in so far as that it is a sufficient model. The school physics model of friction assumes that the surface texture is very much smaller than the contact area, and does not consider heating or wear - all of these favour the larger tyre on an F1 car, but don't much impact on the sole of a hand plane.

Coming back to planes - my favorite Record #5 (was my dads spare) has a bit of a belly (who am I to criticize :lol, and I prefer it that way. It slightly counters the normal tendency to plane slightly convex surfaces.

 

[Dissolve]

Hi,

Using my straight edge and holding the straight edge right against the sole, it seems to sit flush against the sole towards the back of the plane then towards the toe of the plane I can measure around 3-4 thou gap in the last couple of inches from the edge.

I'm not sure if this is going to cause issues or not. My new stones should arrive this week and I'll set up the blade/cap iron before testing.

Worst case scenario.. I'll use my cast iron bandsaw table to lap the sole, any tips/advice for lapping the sole? What sort of grit would you usually begin with?

Thanks

 

[bugbear]

Worst case scenario.. I'll use my cast iron bandsaw table to lap the sole, any tips/advice for lapping the sole? What sort of grit would you usually begin with?

Thanks

I would not even attempt to lap a #7 that way.

BugBear

 

[Dissolve]

Worst case scenario.. I'll use my cast iron bandsaw table to lap the sole, any tips/advice for lapping the sole? What sort of grit would you usually begin with?

Thanks

I would not even attempt to lap a #7 that way.

BugBear

Can you please elaborate? Why?

I'll wait until I have my stones and sharpen it up. Otherwise I'll have to seek a replacement.

 

[Peter Sefton]

We do no 7's using our PSA 80 micron industrial Scary sharp, works well but it will take sometime if it's in a bad shape.
Peter

 

[MMUK]

SO ... what were corrugated soles all about ?

Weren't they designed for use on sappy wood? Less chance of the sole sticking to the goo?

 

[bugbear]

Worst case scenario.. I'll use my cast iron bandsaw table to lap the sole, any tips/advice for lapping the sole? What sort of grit would you usually begin with?

Thanks

I would not even attempt to lap a #7 that way.

BugBear

Can you please elaborate? Why?

1) Your reference surface needs to be much more accurate than the accuracy you want on your plane. It also needs to allow a working stroke of around twice the tool length. I very much doubt your bandsaw meets this requirment.

2) (woodworkers' ) Lapping has a distinct tendancy to dub the ends. Whilst rubbing a tool on a flat, uniformly abrasive surface cannot make the tool hollow, it can easily make it convex, just as a flat plane can make a wooden workpiece convex.

3) Abrasive sheets tend to wear more in the middle, leading to (more!) dubbing at the sides and ends.

Here, from my long defunct webpage, is my description of how best to flatten your plane, should you want to:

Here's my orginal;

http://web.archive.org/web/200905291005 ... atten.html

Here's my "shiny and new"

http://web.archive.org/web/200901141057 ... heory.html
http://web.archive.org/web/200901141455 ... ctice.html

BugBear

 

[MMUK]

You use sandpaper, BugBear? :shock: Shouldn't that be wet and dry for a metal sole?

 

[bugbear]

You use sandpaper, BugBear? :shock: Shouldn't that be wet and dry for a metal sole?

I actually prefer AlZi over SiC, SiC works OK, AloX will also cut.

BugBear

 

[MMUK]

You use sandpaper, BugBear? :shock: Shouldn't that be wet and dry for a metal sole?

I actually prefer AlZi over SiC, SiC works OK, AloX will also cut.

BugBear

Fair enough. :mrgreen:

 

[Corneel]

That's in fact not much different from the method I mentioned above, with one big difference. You were trying to get all of the sole within your flatness specification. I am only concerned about the three important areas, that makes the whole procedure a lot easier and faster. You can even forget about blueprinting on the surface plate and just use a calibrated straightedge.

One other not unmportant thing, don't stress about the flatness of the sole too much. If the plane works fine without inspecting the sole, then don't flatten it! Only when you have troubles using the plane, closer attention to the sole is neccessary.

 

[bugbear]

That's in fact not much different from the method I mentioned above, with one big difference. You were trying to get all of the sole within your flatness specification. I am only concerned about the three important areas, that makes the whole procedure a lot easier and faster. You can even forget about blueprinting on the surface plate and just use a calibrated straightedge.

Yes, but the resulting plane has its wear concentrated on the resulting small areas, which will increase the rate of wear. It's all a compromise.

One other not unmportant thing, don't stress about the flatness of the sole too much. If the plane works fine without inspecting the sole, then don't flatten it! Only when you have troubles using the plane, closer attention to the sole is neccessary.

Yes - there are caveats to this effect on my pages.

BugBear

 

[Corneel]

Yes, but the resulting plane has its wear concentrated on the resulting small areas, which will increase the rate of wear. It's all a compromise.

Sure.

That's one thing you don't hear much about: wear of the sole. It may go slowly on a metal plane, but it does happen. Especially the area in front of the mouth likes to wear a hollow. Planing lots of edges will wear a path down the length of your plane.

 

[bugbear]

Yes, but the resulting plane has its wear concentrated on the resulting small areas, which will increase the rate of wear. It's all a compromise.

Sure.

That's one thing you don't hear much about: wear of the sole. It may go slowly on a metal plane, but it does happen. Especially the area in front of the mouth likes to wear a hollow. Planing lots of edges will wear a path down the length of your plane.

It's something you become very aware of when you flatten an old pane "my way". The hollow in front of the mouth is shown very clearly.

BugBear

 

[MMUK]

One other not unmportant thing, don't stress about the flatness of the sole too much. If the plane works fine without inspecting the sole, then don't flatten it! Only when you have troubles using the plane, closer attention to the sole is neccessary.

Whilst I agree with your statement, I enjoy spending time flattening and polishing the soles of my planes to a mirror finish. I find it very theraputic and much better than spending the day sat in front of the PC 8)

 

[Dissolve]

Looks like I have a decision to make..

I need to decide if I can live with the Discrepancy.

If not do I work on it or send it back? Haha

 

[Trafalgar]

Hi,

I just purchased a damaged No 7 Jointer plane from Rutlands, It had a scuff at the end of the sole which was quickly removed with a very light file and touch with some 1000 grit wet and dry.. That has no bearing on what I'm questioning.

I'm using my bevel edge straight edge (This is straight, it's been checked recently against a very reliable surface plate) to check the sole and it seems to have a bit of a belly near the center of the sole. It's only very slight, but I would much rather have a slight hollow to lap than a bump, how much is acceptable? The plane was labelled as being brand new aside from the scuff on the toe, so if I measure it with feeler gauges and it turns out to be unacceptable I dare say I'll have a delightful exchange with them next week!

What would you guys consider an acceptable tolerance?

A bump is easy to work out on a No. 7. Put medium grit sandpaper in some sort of holder and just sand on top of the bump. This is much easier than removing metal at toe and heel equally to bring down to a swale in the center. This implies lapping the entire sole. I'd much rather just remove a local bump by sanding, again, just the bump. 'Til it's gone or almost gone. Don't fret over the whole thing too much and it will all work out just fine.