[HELP] Possible Lathe Threads

[Hopefuldave]

(04-29-2017, 05:02 PM)EdK Wrote:

(04-29-2017, 04:31 PM)Vinny Wrote: Here's the formula for the tpi of your gears.    

From your pic, I'm going to number (letter) your gears.  

A: 32
B: 64
C: 42
D: 91
E: 86
F: 21
X: 0.94545
Y: LS TPI (8 in your case)

(B/A) * (D/C) * (F/E) * Y * X = TPI.

A word about X.  X is the Kludge factor since the 32 tooth gear isn't spinning at the same speed as the spindle.  X is actually 32/S with S being the number of teeth on the spindle's gear.

I haven't looked at the XLS that Dallen posted, but one thing you need to take into consideration is the distance between the lead screw gear and the 32 tooth stud gear - it could be that they don't mesh or they don't fit.

I'm pretty sure I have my math right, you'll wanna double check it.

Vinny,

The 86 tooth gear is used for metric threads only and the 91 tooth is for imperial threads only. As drawn in the image, just the 91 tooth gear is engaged with other gears. It's kind of hard to see that in the image since the gears are so close in diameter. The 86 tooth gear is just along for the ride since the two form a compound gear.

Also, doesn't the gearing in the gear box have to be included in the formula somehow? The 21 tooth gear would be driving the gears in the gear box which in turn drive the lead screw.

Ed

Simple way to remember the calculation, product of driven gears divided by product of driving gears then multiply by the leadscrew tpi - if Ed's lathe has the 32 on the spindle, then the gearbox has to be 1:1 as described and set for 8 tpi/

(64 x 21 x 91) / (32 x 42 x 91) x 8 tpi - 8 tpi

For metric, it's the opposite, drivers over driven times leadscrew pitch in mm gives you thread pitch in mm

Dave H. (the other one)