12-09-2016, 07:36 PM
This is from the Logan lathe website FAQ. It should provide some insight:
4.1. How can I cut metric threads on a Logan lathe?
4.1.. Logan lathes came with gears for inch threads and an inch leadscrew. The stock Logan lathe can’t cut precisely accurate metric threads without replacing gears.
Some metric threads are close to inch threads. Slight inaccuracy can be accepted in some cases. In those cases, try the nearest inch thread. For example, if you need a metric pitch of 1.0 (1.0 thread per millimeter) you want 25.4 threads per inch. The Logan gearbox can cut 26 threads per inch. That may be accurate enough for a short bolt.
To cut precise metric threads, you need to have a 127 (or multiple of 127) tooth gear in the geartrain. Logan sells a 127 tooth gear for this purpose, but it is expensive. You can cut metric threads that are within 0.02% accuracy using more economical 37 and 47 tooth gears. These are also available from Logan and much more economical.
Here's a chart comparing TPI to Metric thread pitches:
http://www.newmantools.com/tech/pitchconversions.htm
4.1. How can I cut metric threads on a Logan lathe?
4.1.. Logan lathes came with gears for inch threads and an inch leadscrew. The stock Logan lathe can’t cut precisely accurate metric threads without replacing gears.
Some metric threads are close to inch threads. Slight inaccuracy can be accepted in some cases. In those cases, try the nearest inch thread. For example, if you need a metric pitch of 1.0 (1.0 thread per millimeter) you want 25.4 threads per inch. The Logan gearbox can cut 26 threads per inch. That may be accurate enough for a short bolt.
To cut precise metric threads, you need to have a 127 (or multiple of 127) tooth gear in the geartrain. Logan sells a 127 tooth gear for this purpose, but it is expensive. You can cut metric threads that are within 0.02% accuracy using more economical 37 and 47 tooth gears. These are also available from Logan and much more economical.
Here's a chart comparing TPI to Metric thread pitches:
http://www.newmantools.com/tech/pitchconversions.htm
Logan 200, Index 40H Mill, Boyer-Shultz 612 Surface Grinder, HF 4x6 Bandsaw, a shear with no name, ...
the nobucks boutique etsy shop | the nobucks boutique
the nobucks boutique etsy shop | the nobucks boutique