Referring to the picture below the mounting hole will, (hopefuly), be directly in line with either a rib or a gap.
If you name that rib or gap which is inline with the mounting hole 'Number1', then count round anticlockwise until you get to the places I've marked could you let me know how many you counted, either rib or gap?
Hope that made sense
Plus, the mounting holes. what size screw are they made for?
And, could you measure how far from the top or bottom the 7mm internal mounting flange sits?
Wouldn't it be great if we can actually recreate this thing over the internet with just pictures and fag packet drawings?
OK, Sorry for the delay.
My posh Mitutoyo vernier doesn't work either - I think I've got some spare batteries but it's finding the little buggers.
Centre of the screw hole lines up exactly with the edge of a rib, so going anti-clockwise there are five full ribs before the switch recess.
I hope the photo helps somewhat.
Mount screw holes seem to be 3mm and the bottom edge of the plastic ring sits 7mm below the bottom face of the metal case.
There is also the two stage cut out section on the hidden side of each ring - applogies for not mentioning it before.
It starts about 3 ribs befor the switch recess, and carries on for 11 ribs on the other side.
Now the good news.
I've now rescued the tacho ring from a friend who reckons he knows how to strip paint from plastic - he doesn't.
The tacho ring is an exact mirror image of the speedo one - it makes things so much simpler.
Hi again Grewth
Thanks for those pictures.
Hopefully this will be the last.
Refering to the picture below, the red line intersects the centres of the mounting holes, does that look to be in the right place to you, or could it go left or right a bit?
The holes are set at 3.4mm at the moment but that can be adjusted.
Refering to the second picture, can you get me a couple of good pictures directly edge on where I have arrowed so I can see the shape of the cut out profile?
If the profile is rounded could you find something that fits nicely, maybe a Sharpie pen or the shank of a drill bit?
Also could you take some measurements at the three places where I've marked with double arrows?
And finally the mounting lugs, I've set them 7mm down from the top in my cad picture, is that correct, or do they need to be 7mm up from the workplane?
Unfortunately I've been taken hostage by my 94 year old mother at the moment, she is trying to kill me by forcing me to eat trifle until I burst!
I'll get straight onto the plastic rings as soon as I get home this evening.
I've finally got an accurate digital caliper that works.
The position of the mount lugs looks about right to me, dificult to judge without those cut outs included.
In the second picture the depths are from the left 20mm, 23mm, 27mm.
Those lug holes are 3.7mm ID with 70mm between hole centres.
Lugs are 24mm wide where they join the ring.
Tomorrow I'll try and get an accurate offset angle for the switch recess in relation to the mount lugs.
I hope that helps