Harrison L5 change gears

[slowcoach]

Hi all, does anyone out there know what changes gears are required on a Harrison L5 to cut a 6tpi thread. I have no gear chart on the lathe to guide me     hence the plea.

 
Rob

[mklotz]

I'm not familiar with the lathe but, assuming it has an Imperial leadscrew, it should be easy to puzzle out the required ratio.

Say the leadscrew has a pitch of N tpi.  One revolution of the LS will move the carriage 1/N inches.  To cut a 6 tpi thread, you need to have it move 1/6 of an inch for each revolution of the spindle.

Thus the spindle to leadscrew ratio needs to be N/6.  Any set of gears that yields this ratio should do the trick.

[Darren]

There are a couple of downloads here http://www.lathes.co.uk/latheparts/page14.html that will serve you better than the original charts ... 

Select the download suitable for your lathe and away you go .... 

[slowcoach]

Thanks guys, I will have a go at that. 

Rob