Imperial Thread Cutting on Metric 140

[Brad93]

If I have a 127T gear, and a full set of metric changewheels. What other gears do I need to cut imperial threads?

 

[Brad93]

Bearing in mind the imperial machine I’m borrowing the 127T gear from says this to convert imperial to metric.

 

[Morrisman]

Metric change wheels? Aren't they just gear wheels, and the lead screw is either metric or imperial? Been decades since I did any screw cutting though.

 

[Brad93]

The gears I have are.

25
50
60
80
80
100
120

 

[Brad93]

Metric change wheels? Aren't they just gear wheels, and the lead screw is either metric or imperial? Been decades since I did any screw cutting though.

Yeah I have a metric leadscrew with a norton box. I want to cut English threads.

 

[Pete.]

Converting the other way isn't as simple as that imperial to metric chart. Often uses a 127/135tooth gear.

Best idea is find a pic of the proper chart for metric to imperial and sort it out from there.

 

[Gareth J]

If you plug your details into here (or a similar calculator)

http://bilar.co.uk/cgi-bin/change-gear-calculator.pl

It should tell you exactly what you can achieve and how.

Lots of the combinations will need to be disregarded due to the geometry of the lathe but you might find perfection lurks in the tables.

The 127T gear is the key

Edit; that program is for changewheel only lathes. I'm sure there's one that lets you put in the gearbox ratios too but can't find it.

 

[Fastdruid]

If I have a 127T gear, and a full set of metric changewheels. What other gears do I need to cut imperial threads?

You need a 63t on the 140 not a 127t.

Advice on Lathe purchase

heres a few pics I have collected and the Name plates for a 140. Originally the working out of the changewheels and selectors took me ages and ages.Now as suggested I bought a 127T only to find it dont fit in the train or onto the banjo, probably why harrison supplied lathes with a 63 and the...

www.mig-welding.co.uk

 

[Fastdruid]

Chart here for the settings (but as mentioned you need a 50-63/40-120 changewheel combo).

 

[doubleboost]

This is what I use

 

[Brad93]

You need a 63t on the 140 not a 127t.

Advice on Lathe purchase

heres a few pics I have collected and the Name plates for a 140. Originally the working out of the changewheels and selectors took me ages and ages.Now as suggested I bought a 127T only to find it dont fit in the train or onto the banjo, probably why harrison supplied lathes with a 63 and the...

www.mig-welding.co.uk

127 is better than 63.

 

[Fastdruid]

127 is better than 63.

Except if that post is to be believed it doesn't fit on the 140...

 

[Brad93]

Except if that post is to be believed it doesn't fit on the 140...

It fits on an L5. That’s what I’m taking the gear off.

 

[Brad93]

If the graph is to be believed, that has come off the L5 with a two lever norton box. Then I can go 50, 40-60, 127 and get the majority of pitches.

unless the ratios are vastly different on the norton 3 lever box.

 

[Fastdruid]

It fits on an L5. That’s what I’m taking the gear off.

Yes but the point is that it doesn't fit on the 140. I have an L5 so I can't verify that, I'm just going on what others have said.

If it _does_ fit then I calculate it I think 40-60/50-127 would be about right (settings on the norton box as per the charts above).

 

[Fastdruid]

If the graph is to be believed, that has come off the L5 with a two lever norton box. Then I can go 50, 40-60, 127 and get the majority of pitches.

unless the ratios are vastly different on the norton 3 lever box.

View attachment 277817

Yes it is vastly different. Because the L5 has an imperial leadscrew and the 140 has a metric one.

 

[doubleboost]

The 127 wont fit in the casing
that is why I made the 63
the error is very slight compared to a 127
both are a compromise
I do cut lots of imperial threads with mine

 

[Brad93]

The 127 wont fit in the casing
that is why I made the 63
the error is very slight compared to a 127
both are a compromise
I do cut lots of imperial threads with mine

It fits in the L5 though. The cases are exactly the same.

 

[Brad93]

Yes but the point is that it doesn't fit on the 140. I have an L5 so I can't verify that, I'm just going on what others have said.

If it _does_ fit then I calculate it I think 40-60/50-127 would be about right (settings on the norton box as per the charts above).

A 140 has the same casing as a L5

 

[Matchless]

remember I have a Harrison, 12" swing? not sure,