So I have the task of printing these images to a set size 300dpi and 5cm x 3.5cm pretty simple really, I've adjusted the images in photoshop and saved them as a jpeg, when I print them off through photoshop sometimes they come out 5x3.5 others times they are 4.7 x 3.3 cm it's the exact same image used each time and I can't work out if it is photoshop or the printer anyone have any suggestions?
In your printer dialog, check that the scaling is set to none, or 100%.
Just in case, also check the image dimensions are the same each time in Photoshop.
To print at 300dpi at those sizes, the dimensions should be as follows
5cm = 1.9685" x 300 = 590px
3.5cm = 1.37795" x 300 = 413px
By the way, I know the world has gone metric, but for the sake of calculations with dpi (dots per inch) - you need to use inches!