Hey that was quick thank you so much do you know what the 4-40 means

If you're still interested, this is how to identify UNC and UNF threads -

The first '4' refers to the diameter and is probably easiest to 'know how big they are' from this formula below, (I've only just found this - usually you get to know the sizes by rote), and the numbers run from 1 to 12, but the common sizes used are 2,4,6,8 and 10, (unified also covers the miniature screw sizes from 0 to 0000 but these are the same as ISO 68).

The following formula is used to calculate the major diameter of a numbered screw greater than or equal to 0: Major diameter = Screw # × 0.013" + 0.060". For example, a number 10 calculates as: #10 × 0.013" + 0.060" = 0.190" major diameter.

... and the '40' just refers to the 'threads per inch' - each 'number has 2 common tpi values, depending on if its a Coarse of Fine thread.


Mark.