On Sun, Aug 29, 2021 at 6:22 AM Christian Gagneraud 
wrote:

>
>
> Here are the figures:
> Number    mm    inch    mm    Error (%)
> 8    15.44    0.607    15    +6.6
> 7    13.05    0.509    13    +0.7
> 6    11.83    0.465    12    -2.0
> 5    9.78    0.385    10    -2.2
> 4    8.21    0.33    8    +1.7
> 3    7.04    0.277    7    +0.3
> 2    4.97    0.198    5    -0.2
> 1    4.00    0.158    4    +0.0
>
> I can't make any sense of the imperial sizes (eg, numbers are not in
> 8th or a 16th of an inch), but the metric sizes almost match, except
> for #8 maybe.
> However this doesn't sound like a convenient set, the size progression
> is really odd: 4, 5, 7, 8, 10, 12, 13, 15+? The #8 is off by 3/16th of
> an inch
> And then if it's metric, why some random numbers instead of the size in mm.
>
> Hum... Anyone seen something like that?


I have a bunch of mismatched irons, and some are marked, and there is no
rhyme or reason to some that I can measure.  Here is a Samuel Newbould set
for example.  (Text only May thrash this)

1 0.158 5/32
2 0.199 3/16
0.283 9/32
4 0.322 5/16
5 0.406 3/8
8 0.661 5/8


On some of mine, it appears the cutting edge is wider than the body, and as
you shorten the blade thru use, it gets narrower.

Of my 38 stray irons, none is a perfect fraction using a digital caliper,
which is not terribly surprising.

Somewhere I saw a table of sizes by number, maybe a Marples catalog.  Will
add it later if I find it, but it did show a logical fractional inch
transition .  Here is a cat cut from 1938, just listing it as sizes in a set

https://archive.org/details/wm-marples-and-sons-1938/page/26/mode/1up


Kirk in Half Moon Bay, CA, about to walk the dogs to avoid the heat and
tourists.

-- 
Sent from my iPad, apologies for the Auto Correct errors. Kirk