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When I purchased my lathe I was told the lathe is made in different factory’s at different times, sometimes they come with a 16mm tool post and sometimes a 12mm tool post, could be a similar thing with the dial. It’s a bit odd though the 20 tooth gear works out a bit better. I modified my table to (I think) suit your lathe, it’ Give you an idea of what threads will work anywhere and which ones won’t. When I get my computer back on the internet I’ll post the spreadsheet if that’s useful.
Yes the spreadsheet would be a great help. That way I can understand your calculations.
Kpar
 
I finally decided to have another crack at single point threading following my past failures.
I have an AL-320G lathe with a metric leadscrew. I changed the gears for a 1.5 pitch on a 16mm rod.
I ran into problems engaging the half nut, then decided to leave it engaged and reverse the lathe.
Finally got the thread I required.
My questions are.-my thread dial has 6 numbers (not 4) and seems to have 2 engaging spots between numbers easy to select the wrong one ?
Also how much end play should be in the leadscrew ?. With the machine turned off & half nut engaged if I move the carriage back & forth
the lead screw moves 1/8" is this normal ?.

Kpar
The four marks are used for an inch thread system based on even or odd thread combinations. A metric thread offers more combinations and requires a chart for the dial. You need the instruction or a chart to select when to put the half nuts in. ON a south bend metric lathe you not only need the chart but you have to select the gear that meshes with the lead screw.

Sorry I cant be more help but when I looked at the operational manual for your lathe it seemed short of some basic information.
 
The four marks are used for an inch thread system based on even or odd thread combinations. A metric thread offers more combinations and requires a chart for the dial. You need the instruction or a chart to select when to put the half nuts in. ON a south bend metric lathe you not only need the chart but you have to select the gear that meshes with the lead screw.

Sorry I cant be more help but when I looked at the operational manual for your lathe it seemed short of some basic information.

Like HMEL wrote, industrial lathes, in my case a Colchester VS2500, have thread indicators with a series of five or six gears which need to be interchanged depending on the pitch to be cut. Metric pitches simply don't lend themselves to a simple indicator.

I spent over 30 years in industry. The lathes I used had reversing clutches (instantaneous reversal) and camlock chuck mountings, so the chucks couldn't unscrew.

I never once saw a turner disengage his halfnuts and use a TDI.

Andrew UK
 
Yes the spreadsheet would be a great help. That way I can understand your calculations.
Kpar
See attached for what I calculated for your lathe based on the information you have given, hopefully it makes sense, have a look and try a few different threads out.
 

Attachments

  • AL320_Thread Chasing Dial 24 tooth dial.xls
    38.5 KB · Views: 7
See attached for what I calculated for your lathe based on the information you have given, hopefully it makes sense, have a look and try a few different threads out.
Thanks for that. Will do some experimenting when I get some free time
Kpar
 

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