Metric Harrison 190 cutting imperial thread

I have a friend you wants to cut an imperial thread on a Metric Harrison 190, he has required gear train but he can't find the gear position or the setting for box.

can any one help

Thanks

Stew

Hi Stew,
If you can give us a list of all the change gears he has, the pitch of the leadscrew and all the ratios that the gearbox between the leadscrew and the screwcutting gearbox input shaft has then I think many of us will be able to work out how to do it. Also what imperial TPI value (Or values) does he require.

Les.

Is the 190 the same as this

If so that gearbox may be dual purpose as in just dial in whatever pitch thread metric or imperial like newer Harrisons and Colchesters no need to change change wheels. What you really want to know is what the lettering corresponds to on the main 4 levers, lower right would be direction. Assume he has a full set of change wheels, extremely hard to come by.

Whats the chart above on head stock?

Did have the 140 flat top which is same as a mates round top 11" both with Norton gearbox. In this instance its just one change wheel to swap over but dependant upon pitch.

Hi Jon

Thanks for your reply, my friend struggles a bit with forums and has asked me to responds for him:-

This is the email me sent me:-

I see on the model engineering site we have a reply that sounds promising the chap ( Jon ) as sent a photo asking if it is of the same lathe the answer is yes cannot understand is explanation our chart definitely only shows metric pitches no mention any were about English TPI