Screw thread sizes - antique French barrel clock

[MikeEll]

Hi all.  I'm working on an antique French barrel clock movement at the moment.  It has a mangled thread for the shoulder screw that holds the click in place.  I can replace the screw fairly simply but I need to try and clean up the thread in the plate.  Hopefully there's enough material to hold the screw once I've run a tap through it.  Any idea what type of threads these old French clocks would have used, please?

[oldhippy]

They are a french size thread so unless you make a tap or have one made you will need English size. 

[RichardHarris123]

Do you mean re-tap to an English size?  Are modern clocks made with metric threads? 

[Dell]

Depending upon when it was manufactured it could be Thury, Löwenherz, BA, Metric or even made with a thread plate as oldhippy said best re tap and make a new screw with the head to match any other screws , my suggestion would be either BA or Metric and as both threads are very similar with BA being based upon the metric measurement no one would know apart from you.

just my suggestion Dell

[MikeEll]

Thanks guys.  I have a few spare screws from a similar French clock on the way.  Was hoping to identify the thread on those if possible.  Will try some thread gauges on it and see if I can find a metric or BA tap with similar diam/pitch