Just read tghis whole thread. Topic veered into Lee Valley vesus
Lei-Nielson verus Chinese planes versus Anant planes from India. I
suggests looking at the planes from Steve Knight at
http://www.knight-toolworks.com/ .

Regarding the original question: "is there significance in flatness or
speed of work between the three. Given that the different planes are
made, there must be a reason why.......".. I thinks it's just a matter
of accuracy. My feeling is that there's a significant difference
between a #6 and #7 but much less between a #7 and #8.

For readers who might have an engineering abckground, these planes
operate like low pass filters. If the length of the plane is L, then
the plane has (approximately) a low pass response which is a sinc
function whose first null is at 1/L.

So we compare 1/18 versus 1/22 versus 1/24: 0.0555 versus 0.04545
versus 0.04166. If you plotted the responses, you'd see the smaller
number means more "dc" rejection. To a first order, we can directly
compare these numbers:
the 24" is about 9% better than the 22".
the 22" is about 22% better than the 18".

Hope I did the arithmetic correctly....





"Sam the Cat" wrote in message ...
Hey all

Looking to into jointing a board with a hand plane and trying to select
the appropriate type planes.

I can understand that the long the plane the less likely the plane is to
"follow the curve" but given that I can get a #6 at 18", a #7 at 22" and a
#8 at 24" is there significance in flatness or speed of work between the
three. Given that the different planes are made, there must be a reason
why.......

Cheers
Eric (a normite in neander territory)