Hi Galoots,

I recently bought a set of Mathieson plough irons.
They are all in very good condition, marked from 1 to 8, all with the
same stamp at the same location "ALEX. MATHIESON GLASGOW".
This looks like an original set to me and by the look of it, they have
been barely used.
I'm thinking of making a nice box for them, to go with a Mathieson No
4 plough plane I'm restorating right now.

The sizes puzzle me, it looks almost like a metric set, as I can't
make any sense of the imperial sizes.

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?

Will post photos soon.

Chris.
1 AM, Monday here in locked down NZ.

PS: I tried to measure the imperial sizes with a wood/brass stanley
caliper (thank you galootaclaus), but had to resort to my digital
caliper.