27 February 2011

Hollow and round planes - 4

Contrary to my expectations and 40 days late (or later) the second package with the six planes finally arrived.  The package was battered but the planes were all in good condition.
The set completed,  3 pairs and 4 singles, the bottom row before cleanup.

The blades still in their original "The irons all need cleaning as there is some rust. A worthwhile project." state

The round 6, shortened,  the only damaged part of the set.  Seen after a first cleanup on my cheap oil-stone (I think it is made of concrete),  that I keep dry.  The tip shows some dip, so  I could have used the ruler trick,  but I finished it by lightly polishing it on a hard felt wheel with some Veritas green rouge.

 This morning I spotted on ebay four planes of unspecified size, I thought it was a pair of 8 and a round 12 and 14,  three of the four I am missing to have matched pairs.  Made a half hearted attempt with a  21 £ bid and lost from a late(r) sniper. Anyway for now it's more important to use them.

26 February 2011

Hollow and round planes - 3

Working with Sketchup I look further how to sharpen with sandpaper or rouge set on a profile cut with an hollow plane.  Due to the relief angle the bevel of a hollow does not fit its cutted profile, as setting the bevel in contact with the profile covered with an abrasive creates a deeper profile.  To solve this I look at the effect of two variations with the help of sketchup drawings: the ruler trick and sharpening on a different profile.

Using the ruler trick is unorthodox as it is a not done with profiled planes and once used there is no easy way back. On the other hand the used plane blades I have the top is worn out at the edge and are good candidates for using th trick.

To test the effect of the ruler trick set on an angle of 5°.  That's more than the 1 to 3° I expect in real life. So I drew a blade with a relief angle of 15° and cut of the top on 5° and looked at the end profile compared to the original.  Well there is a shadow of a change, but most probably it would be difficult to measure the difference in real life.

 The drawing shows that even after the ruler trick the original profile is unchanged.  I changed the end result from hollow to round, and when I join the two I get a near perfect fit, ... my word.

Another idea is to use a larger profile (covered with an abrasive) to sharpen the bevel to compensate for the difference in profile.  So I looked in Sketchup what profile fits a 10 bevel and found that a 14 is close.

The drawing shows from right to left the plane and its profile.  The profile change when it is set flat to the bevel when the relief is 15°.  And as first the nearly perfect fit of a 10 bevel on a 14 profile.

12 February 2011

Hollow and round planes - 2

Still nothing about my 6 missing hollow and round planes.  This more or less ends my current perspectives to experiment with profile planes.  Let's go virtual.
I finally did what I intended,  trying Sketchup out as a way to look at problems when sharpening a blade on sandpaper on a profile set with the plane.

- I drew an arc 10 wide with radius 10.  I discovered I could do that by entering 10 and 10R to set the arc.  I already downloaded a arc: center and 2 points plugin to emulate compass work.  That's the frustrating part of Sketchup,  it is good but far away of descriptive geometry techniques. Where is my Sketchup divider compass?
- Made a surface of it and extruded it to volume and made it again a surface by deleting the bottom surface.
- Intersected it with two planes at 45° and 30°.  Checking literature I found that a relief angle must be between 10 (11) and 15°.  Seeing that the edge of the blade shows depressions and cracks in the corner for hollows,  a low relief angle is better for the edge.  But with an extreme relief of say 0°, the blade would not dig into the wood and shavings caught between blade and workpiece could slide along unharmed.
- By selecting the two surfaces I could let Sketchup create the intersection line. After that I grabbed the two intersected planes and flipped them on top of each other.
The result are two different ellipses. Ellipses? I should have remembered my trigonometry and put, at last, my sin() and cos() functions to good use.

The result shows there is a difference,  and for hollows it is a problem as the sides of the plane will dig in. A first solution is to sharpen on a bigger profile, a 10 on a 12 profile etc.  The next idea that comes to my mind is the ruler trick.  Applying the ruler trick to a hollow would thin out the sides and make them less deep.  So it would weaken the sides of the blade (that's bad), but also make the curve shallower (that's good if you already messed up the depth).

I need to model the ruler trick with a profiled blade.  Another aspect I need to look at is sandpaper thickness. Certainly for smaller planes  the thickness of the sandpaper influences the geometry.