Im Working on covering a scanned image of a pcb to a vector file, but the only component that I can use to scale is a Trimpot.
Right now I'm getting the following measurements
4mm pin spacing, and 3mm deep. (An not knowing the range of trimpot pitches I dont know how right that is)
But due to the nature of this type of scaling up, knowing the published board size is often a few mm different to the actual board size!
So what pitch should I be scaling to? 
4mm pin spacing, and 3mm deep
I have a few of these type pots and the dimension that you specify as 4mm seems to be more like 4.5mm on mine.
Don
Some designs of these miniature open pots also have flat tab connectors rather than round pins. The circuit board holes for these are actually small slots.
It is my inderstanding that the use of "trimpot" to describe this component is confusing, since I have always understood trimpots to refer to the multi-turn miniature devices that is invariably built as a blue plastic package
jack
Some designs of these miniature open pots also have flat tab connectors rather than round pins
Mine are like that.
It is my inderstanding that the use of "trimpot" to describe this component is confusing, since I have always understood trimpots to refer to the multi-turn miniature devices that is invariably built as a blue plastic package
The device in question should be called by a generic name such as "trimmer" since the trademarked name "Trimpot" belongs to Bourns. Bourns has the same problem as the owners of "Jeep", "Kleenex", "Frigidaire", etc. have. Sorry - I don't have any UK specific examples.
Don
Looking at the photo I would guess that this is a standard vertical trimmer with a pin spacing of 0.2"x 0.1". Take a look around the RS or Farnell website, there are plenty of datasheets available for these items.
I would simply call it a pot, as a trimmer to me has always implied multi-turn precision adjustable.
Lefty
a trimmer to me has always implied multi-turn precision adjustable.
I think the "real" difference is in the number of times that you are supposed to change te setting. A "trimpot" is something that you're supposed to adjust "few" time, and then leave there, while a pot used as a volume control (for example) should be designed to be turned up an down thousands of times. (somewhere in the datasheets area specs for such things...)
Well I was thinking in terms of actually being able to precisely adjust to a specific value. A typical 20 turn pot give one the ability to make critical adjustments, say balance trim control on a instrumentation op-amp that has significant gain. Those single turn 'trimmers' shown in picture are not usable in many cases because of the friction, backlash and limited mechanical travel, while a 20 turn pot gives a 20:1 advantage at least, thus great for 'trimming' applications. The cost difference between the two kinds (single turn Vs muliturn) says much about their intended application.
As one who worked in field service for years I can sure tell you which kind of pots were suitable for 'trimming' adjustments and which were not. 
Lefty
trimming is any adjustment to compensate for variation in component values, irrespective of whether it's high-precision 20 turn cermet or a carbon preset.
I'd suggest that this pot is 0.2" by something that might or might not be 0.1"