4mm2 twin and earth cable

"OK ebee, fair enough to suggest that a vernier is not really accurate enough, but is accuracy the problem, it more likely to be resolution. Here is a picture of a fairly modern digital micrometer, resolution 1 microm (1/1000 mm). Its accuracy is usually +- 2 or 3 microns."


Hi Dave, microns - often referred to as "mouses tails" .


Yes just to clarify a little yes most of those engineers knew about accuracy and resolution and it was during  the pre calculator era.

They made bits for jet engines and the engineers had instruments, inspection had better ones, quality control had many sets of different usage and calibration in a temperature controlled environment. Monthly all the shop floor instruments were (in rotation) collected one day, left to stabilise temperature next day then tested and returned on day 3. If they passed they got a brand new "METROLOGY" sticker on them. Precision slip gauges and interference bands and all sorts of lovellys. Non were allowed on the shop floor without the current or last months sticker on them - including their own private tools. All traceble back to the NPL (National Physics Lab) I took mine in a few times, it was an old 0 to 1 inch micrometer, my Grandad gave it to me, tested OK but for measuring face up to 2/10 thou over the outer one third of the faces, so OK for flat work but not on round work, Obviously OK for my home use.

There was a laugh one day when they sent a brand new vernier caliper gauge , say 4` or 5` I think it was. They complained it was almost 2 though out on some of its range. Moore and Wright wrote back that this caliper was OK, the accurate part was the last foot of its range and that was only guaranteed to within 5 thou when new. They`d been using them to nearest thou i.e. with half a though presumed accuracy for years - probably shows just how good Moore & Wright and others were back then and how disciplined staff with robust regimes could be in practice much of the time I suspect.


I suppose in our world we might liken some of it to the practice of using a club knife or "stanley knife" etc to slide down the earthwire of a T & E cable without nicking it or the insulation, takes a lot of practice before it becomes second nature, our old R E B used to get this taught at college, I think sucking of teeth might happen nowadays. (Actually it might be one reason that I have an aversion to using a cpc as a cheeswire!)


Of course I might be a little deluded !

"OK ebee, fair enough to suggest that a vernier is not really accurate enough, but is accuracy the problem, it more likely to be resolution. Here is a picture of a fairly modern digital micrometer, resolution 1 microm (1/1000 mm). Its accuracy is usually +- 2 or 3 microns."


Hi Dave, microns - often referred to as "mouses tails" .


Yes just to clarify a little yes most of those engineers knew about accuracy and resolution and it was during  the pre calculator era.

They made bits for jet engines and the engineers had instruments, inspection had better ones, quality control had many sets of different usage and calibration in a temperature controlled environment. Monthly all the shop floor instruments were (in rotation) collected one day, left to stabilise temperature next day then tested and returned on day 3. If they passed they got a brand new "METROLOGY" sticker on them. Precision slip gauges and interference bands and all sorts of lovellys. Non were allowed on the shop floor without the current or last months sticker on them - including their own private tools. All traceble back to the NPL (National Physics Lab) I took mine in a few times, it was an old 0 to 1 inch micrometer, my Grandad gave it to me, tested OK but for measuring face up to 2/10 thou over the outer one third of the faces, so OK for flat work but not on round work, Obviously OK for my home use.

There was a laugh one day when they sent a brand new vernier caliper gauge , say 4` or 5` I think it was. They complained it was almost 2 though out on some of its range. Moore and Wright wrote back that this caliper was OK, the accurate part was the last foot of its range and that was only guaranteed to within 5 thou when new. They`d been using them to nearest thou i.e. with half a though presumed accuracy for years - probably shows just how good Moore & Wright and others were back then and how disciplined staff with robust regimes could be in practice much of the time I suspect.


I suppose in our world we might liken some of it to the practice of using a club knife or "stanley knife" etc to slide down the earthwire of a T & E cable without nicking it or the insulation, takes a lot of practice before it becomes second nature, our old R E B used to get this taught at college, I think sucking of teeth might happen nowadays. (Actually it might be one reason that I have an aversion to using a cpc as a cheeswire!)


Of course I might be a little deluded !