Plane shape (coffin v bailey)

[newt]

Having read several books on hand planes during my forced convalescence there is one aspect that I have not found any satisfactory explanations. During the period when planes were made to a very high quality there emerged to distinct shapes, the parallel sided bailey type plane and the coffin shaped plane (mainly smoothers) made in both steel and wood. Some of the Norris planes are a good example. Other than the reduction in surface area (assuming a similar length) and perhaps balance (centre of gravity over the blade cutting edge), what is the benefit if any for the rather nice coffin shape, could it have been just fashion. I can see on the tote-less wooden planes that the narrow end may be easier to grip, but that would not be the case with totes. It must have been more difficult to manufacture. Just interested.

 

[Philly]

Pete
What about reduced friction?
Personally I reckon it is for looks - the coffin shape is very graceful. And you know how we woodies like the pretty toys..... :lol: :wink:
Hope this helps
Philly

 

[newt]

Philly, yes I think it is for looks. Friction is not directly dependant on area but there may be a small reduction in the suction. I like the shape, however given that they must be more difficult to make, it does surprise me that they are just a fashion statement.

regards pete

 

[pam niedermayer]

There are those who say that the coffin shape, with a high percentage of end grain exposure, is more amenable to satisfactory moisture management.

Pam

 

[jmk89]

There are those who say that the coffin shape, with a high percentage of end grain exposure, is more amenable to satisfactory moisture management.

Pam

Pam

I'm not sure that I understand that comment. If we were comparing a "square" woodie with a coffin shaped woodie, I think I would understand - I may not agree, but I would understand :wink:

But aren't we comparing coffin with Bailley pattern? In which case the only wood involved is any infill and the knobs and totes. Or have I missed something?

Cheers

Jeremy

 

[pam niedermayer]

Yeah, I suppose you were, didn't read carefully enough.

Pam

 

[Paul Kierstead]

But aren't we comparing coffin with Bailley pattern? In which case the only wood involved is any infill and the knobs and totes. Or have I missed something?

If you insist, your comparison may be faulty, since the reasons they are the shape they are may be nothing to do with their utilization. As Pam pointed out, the coffin may be that shape to offset at limitation in woodie design (although infills are also often coffin shaped, why is not clear). Bailey's are almost certainly straight sided as a consequence of manufacturing issues; the reasons for curved sides would have to be extremely compelling to overcome the very significant added manufacturing cost.

In short, you are probably comparing apples and oranges and are trying to draw a comparison which is based on an assumption of an functionality of design which does not, in fact, hold.

 

[newt]

For wooden planes Pam has a point, I see on the LV site, they describe making a wooden straight edge. To minimize wood movement it is suggested that the side opposite the straight edge is curved to expose more end grain. On the basis that wooden planes came first in time, it could be that the steel versions are just copies of the general shape, perhaps because it looks nice.

 

[Wiley Horne]

Newt,

I think you have it exactly right. With respect to coffin-shaped woodies, the received wisdom is what Pam and Paul and you have said: the coffin shape exposes more end grain along the sides of the plane. Here is a detailed analysis of the situation, by Larry Williams and Bill Clark:

"There's another thing happening with bench planes. The body of a bench plane is divided into three sections. The toe and heel sections are solid wood and the escapement has only air and thin sides or cheeks that have a triangular shape. These thin cheeks absorb or lose moisture faster than the solid thick sections. As they expand and contract more than the adjacent solid sides, they force the planes of the soles of the heel and toe out of alignment. This is taken care of on the traditional smooth plane by the coffin shape which exposes the end grain of the sides. The sides of the heel and toe thus are able to maintain a similar moisture content as the cheeks." Ref: www.planemaker.com/articles_tuning.html

Then the question arises, why was the coffin shape carried forward into infills, given the greater difficulty of manufacture? I would not argue with the idea that the infill makers went with tradition and aesthetics in manufacturing the coffin shape. However, if one picks up a parallel sided A6 and then compares with a coffin-sided A5, it will be seen--to me at least!-- that the A5 has a little better balance in the hand. The coffin shape removes weight from the toe of the plane, so there is less weight cantilevered beyond the user's handhold on the tote. The difference is noticeable as it affects balance of the plane.

With respect to Bailey shape, surely Paul (and maybe others?) have it right--manufacturing efficiency governed.

Wiley

 

[David C]

Wiley,

What a splendid answer,

thank you,

David