Permanent magnet based magnetiser

A magnetiser comprising a housing, a passage arranged inside the housing, and a permanent magnet assembly arranged outside the passage to provide a magnetic field passing through the passage, said housing comprising an inlet to the passage and an outlet from the passage such that an object to be magnetised can be inserted into the passage via the inlet in the housing and removed via the outlet in the housing, wherein the passage includes:

• a. a uniform portion where opposing surfaces of the permanent magnet assembly are arranged a uniform distance apart along the length of the uniform portion;
• and
• b. a diverging portion arranged between one end of the uniform portion of the passage and the outlet of the housing where opposing surfaces of the permanent magnet assembly diverge such that the distance between opposing surfaces of the diverging portion nearest the uniform portion is less than the distance between opposing surfaces of the diverging portion nearest the outlet;
• c. wherein the average angle (B) of the normal vector of the opposing surfaces of the diverging portion to a longitudinal centre axis of the passage is greater than 45 degrees.