Thread Dial

[Kpar]

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

 

[HMEL]

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.

 

[methuselah1]

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

 

[HCNZ]

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.

 

[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.

Thanks for that. Will do some experimenting when I get some free time
Kpar