Replacing the dial face of a modern tachometer with the original

Some years ago I bought a quite expensive Smiths 8000 RPM tachometer, it was excellent but for some reason I bought one with a white dial and I never liked the look of it.

However, I do have plenty of original Spitfire tachometers, both from MKIII/IVs and 1500s so at some point I decided that I could simply swap the dial, needle and glass/bezel for that of a 1500 Spit and I’d have what looked like an original tachometer, but underneath it’d be a modern stepper motor driven unit capable of handling 8000 revs.

I recently did this again to swap the 1500 dial for my original MKIV one for a couple of reasons; firstly, I prefer the look of it and secondly, the 1500 one seemed to have worked loose and occasionally the needle would stick on it.

It’s a fairly easy process.

Step 1 is to dismantle the target tachometer, the bezel should come off by gently teasing the tabs on the back.

Lining up

Careful not to get too many oily fingerprints on the glass

Secondly you’ll need to remove the needle.  This can be delicate, but basically it is just going to pull off.  The easiest way to do this is with a couple of teaspoons.

Thirdly, I marked up where the 0 and 7000 RPM points were on the original scale and removed the original face.

Next, I just lined up the original face with the markings (or as close as you can get) and the center hole – this is important because there stepper motor is very delicate and any friction on the needle will very likely stop it working.

Behind the face is a plastic screen, which I drilled to accept the screws from the original face and then put it all back together.

Here it is before re-installing the glass.