Any hope for metric threads without change gears

[Shotgun]

3D printed gears work fine.

Not if the teeth of the gears can't reach each other.

 

[JimDawson]

Have you tried 1.5mm? Will 5.5% error be close enough?

No, I haven't that I remember. But in the next few says I'm going to do a M75x2 thread, we'll see how that works out with 2.36 error.

I would just make a test cut and see how that works out.

 

[mickri]

PM sent to Shotgun

 

[whitmore]

Not if the teeth of the gears can't reach each other.

[about 3d printed gears]

I think the spacing of the shafts is one known, and the ratio of the pitch diameters of the gears
is the other known. That ratio being a small-integer ratio with one integer being 127, ideally.
There is a solution to the two values (pitch diameters) that works, it just won't usually
have a tooth size that would mesh with the metal gears' standard teeth. Printed gears don't
need to be designed for standard tool cutters.

To drive the metal gear teeth, a metal gear is pinned alongside (rotates with) the printed gear.

 

[Cyclebuster]

my Walcott is listed in the brochure as being able to cut "other" threads with optional change gears. I have them, but i dont have a clue where to use them or how to calculate the pitch before or after.

 

[Shotgun]

Search for a website called "ride the gear train" to get yourself edumacated about how to mix and match.
Can't help on where to add them to your particular lathe.

 

[Asm109]

Whether a nut with the wrong pitch will work with a given thread depends on two things.
1. Length of engagement ie , how thick is the nut.
2. clearance between flanks of the threads at the pitch diameter.

1.5mm pitch compared to 16 tpi 5.5% error (from table above).
1.5*.055=.0825 mm .
every turn of the nut needs .08 mm of clearance to avoid jamming.
A nut 1 or two turns could be made to work. More than that would require cutting the male threads so deep (thin) that there would be no strength.

 

[phubbman]

What if you just used an off-the-shelf chuck like this and made your own 4” back plate to fit your spindle? It doesn’t answer how to cut metric threads on your lathe, but it gets you where you want to go.

 

[Shotgun]

That's a good option, @phubbman , but not quite where I want to be.