Dimensioning backsaw plate.

[swagman]

IMO. Where length is given a value; depth could be calculated using a predetermined ratio. For example; if a saw plate of a starting blank size of 12 inch in length x 3 inch in depth is deemed an ascetically ideal ratio to work from, this can then be transposed to give us a base value of 4 to 1.

From that; a simple formula can then be applied to determine the ideal depth of saw plate that would comparatively match different lengths of plate size.

Formula: D=L X 0.25.

examples;

8 inch plate; D = 8 X 0.25 ( 2 inches)
10 inch plate; D = 10 X 0.25 ( 2.5 inches)
11 inch plate; D = 11 X 0.25 (2.75 inches)
12 inch plate; D = 12 X 0.25 ( 3 inches)
13 inch plate; D = 13 X 0.25 (3.25 inches)
14 inch plate; D = 14 X 0.25 ( 3.5 inches)
15 inch plate; D = 15 X 0.25 (3.75 inches)
16 inch plate; D = 16 X 0.25 ( 4 inches)

To then work out what gauge of saw plate is needed to suit the depth of plate being used; another general guide could be put together.

examples;

1 1/2 to 2 inch below the spine. (0.015 / 0.018 / 0.020)

2 1/4 to 3 inch below the spine. (0.020 / 0.025)

3 1/4 to 4 inch below the spine. (0.025)

4 1/4 to 5 inch below the spine. (0.032)

Thoughts anyone.

Stewie;

 

[Cheshirechappie]

Might be better to suit blade dimensions to the intended duty of the saw. A dovetail saw intended mostly for drawer sides and small box work doesn't need a deep blade - 1 1/4" might be enough - so could tolerate being at the thinner end of the range. A tenon saw intended for heavy framing work on site would need to long, deep and thicker - say 18" x 5" with a 0.040" blade.

There seems to be a fashion for thinner sawblades in recent years. Comparing the thicknesses you quote above (which correspond with thicknesses commonly quoted by the current quality and bespoke makers) with older saws is interesting - I have a Thomas Turner dovetail saw made about 1900 which has a superbly comfortable handle, 9" long x 2" blade depth, which has a blade of 0.025" thick. It works fine, and it has survived a century of use and abuse without any kinks to the blade.

As with most design work, in the end it's a matter of finding the acceptable compromise between lightness of use, speed of cut and ability to absorb the rough-and-tumble of day-to-day workshop life. The 'bespoke' saws can get away with thinner blades because they can reasonably expect to be cosseted a bit more. A tool made for everyday use would have to be a bit more solid. The designer and maker are also constrained by the available thicknesses of stock spring steel.

Don't think there's a 'right' answer - it's down to the maker, really.

 

[AndyT]

+1 to what CC said.

The m ore I look into tool history the more examples I find to show that the high degree to which woodworking tools were standardised made sense.

There is a handy chart in Holtzapffel, volume 2, page 699 which relates saws to their sizes and uses.

 

[swagman]

Hi Andy and CC. Thankyou for thoughts. I think it would be opportune to point out that what I am attempting to do is supply a general resource guide that can be utilized by forum members who wish to try their hand at making their own backsaw using more modern saw making techniques & materials. A good example is the trend towards slotted versus folded backs. Good discussion has occurred in the past has covered a lot of critical areas of backsaw construction. Albeit little with regards guiding those interested in the knowledge of how to size the saw plate proportionally to achieve a visually balanced outcome. The same can be also be said with regards choosing the right gauge of saw plate to suit the depth of plate in mind. I accept their is a lot to be still learnt from studying early examples of saw makers work, but one should keep in mind that the trend of plate size & gauge being used by these earlier saw makers has changed in modern times to include a movement towards using thinner gauge saw plate. As such each seems reasonable to conclude that the parameters of using such thinner saw plate should be clearly outlined in some form that will enable others to have good access to that knowledge.

regards; Stewie.

 

[swagman]

After discussions with Isaac Smith the following is a revision of my previous recommendations.

Stewie;


IMO. Where length is given a value; depth could be calculated using a predetermined ratio. For example; if a saw plate of a starting blank size of 12 inch in length x 3 inch in depth is deemed an ideal ratio to work from, this can then be transposed to give us a base value of 4 to 1.

Formula: D=L X 0.25.

(pre-spine depth of plate)

8 inch plate; D = 8 X 0.25 ( 2 inches)

10 inch plate; D = 10 X 0.25 ( 2.5 inches)

11 inch plate; D = 11 X 0.25 (2.75 inches)

12 inch plate; D = 12 X 0.25 ( 3 inches)

13 inch plate; D = 13 X 0.25 (3.25 inches)

14 inch plate; D = 14 X 0.25 ( 3.5 inches)

15 inch plate; D = 15 X 0.25 (3.75 inches)

16 inch plate; D = 16 X 0.25 ( 4 inches)


Saw Plate Gauge. (pre-spine depth of plate)

Up to 1 1/2 inch (0.015 / 0.018)

1 1/2 to 2 inch (0.018 / 0.020)

2 1/4 to 3 inch (0.020 / 0.025)

3 1/4 to 4 inch (0.025 / 0.032)

4 1/4 to 5 inch (0.032)