rotary cutting blades
 

I've used my cutters for the last 20 years. I was wondering what/why there is numbers on them. Are they there to know when to change them exactly or what, I've looked online to no avail.

What brand do you have and where are these numbers?? They may just refer to a production form that is used to make a part of the cutter.

I think it is from Fiskars . The lines & numbers are along the edge of blade, like a pizza crust. Tried taking a picture but they don't show. Also they have lines in between the numbers like a ruler. I will look on fiskars site

I found an example from google rotary blades images, what do you think?

l just buy replacements by size, eg. 45mm, 65 mm. l have found most blade makes interchangeable.

I've seen those lines but never really thought about it!

The numbers are on Olfa Blades. Here's the explanation from the olfa site,
https://www.olfa.com/faqs-olfa.html

08. What do the numbers around the perimeter of the rotary blades mean?The original rotary blade was designed to fit a safety cutter that positioned each section of the rotary blade in a fixed position to be used upon the dulling of the previous section. The numbers represented each of those sections. When OLFA introduced the original rotary cutter in 1979, the numbers became irrelevant, but have been maintained as a sort of historical feature representing the original rotary blade.

Thanks, Paper Princess ! That's good to know, I suppose...

Thanks for asking! I've wondered about that, too and no-one had an answer! Now we both know! Thanks PaperPrincess!