At Bunnings today I bought a H4 treated pine sleeper - 200mm X 50mm - 3m.
Looking at the pile, I noticed they all had chamfered edges on two sides - the staff member that helped me load it onto my trailer said it was done to prevent the wood bowing, but didn't know how.
Neither do I.
Something to do with timber 'physics' when it dries out?
That's a very interesting question. I believe some manufacturers chamfer the timber for ease of handling and to avoid getting cut by the sharp edge of the timber. I've read through forums that it is used to increase their fire resistance. Thin corners of wood are easily ignited, so removing them through chamfering makes it more difficult for the timber to catch on fire.
I would suggest that due to the shortage of timber they are using the timber that is damage on the edges, and would possibly be rejected. looking at the size of the champers may suggest using a lower grade product
Hobbling around Bunnings today - I revisited the stack of sleepers. Maybe a lotta other people asked the same question as there are now numerous billboards in front of them explaining the reason -
It looks like you've solved the mystery, @Noyade! I liked @r23on's theory, but the chamfers are on the wrong set of corners to be cutting off sapwood or where they couldn't mill the entire board out of the log.
I do like the look of the chamfer, though. Something a little different.
Thanks for updating us.