On Mon, 30 Aug 2021 at 02:51, Kirk Eppler  wrote:

>
> 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
>
>
Wow, #1, 2, 3 and 4 are a pretty good match! 5, almost, and 8 spot on!

Now why 5/32 and 9/32? a little bit smaller than 3/16 and 5/16? Are these
common thicknesses in the weirdysystemofunit world? :)
3/16 is a little bit smaller than 1/4, and so on...
The "almost matches" metric size was likely just a funny coincidence.


> 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.
>

Definitely, same here.


> 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
>

Interesting, from 1/8 to 9/16. They don't give the list tho :(

Looking at dado and plough iron list that came with the 55, it looks a bit
more organised.


Thanks,
Chris