See attached jpeg showing the thread cut for various configurations on my Hercus 9"
I see on the web that various other lathes have a similar plate.
What I dont understand is the assumptions behind the calculated values.
From what I have read, I currently think that the critical factors are
1. TPI on leadscrew
2. Number of teeth on stud gear
3. Number of teeth on final gear
4. Whether or not a compound gear is involved
5. Gearbox ratio (if you have a gearbox)
The way I see it, its reasonable to assume items 1, 2 and 5 were known by the people who calculated the values on the plate, (different values for item 2 are listed on the table)
They must have assumed something for items 3 and 4 ?
I've set up a spreadsheet for my lathe change gears and gearbox ratios and can calculate the TPI for various configurations and these calcs agree with VernonV's Latheworks program, so I think I understand the basic maths but I don't understand how anybody could print that plate without saying what they had assumed for items 3 and 4.
Any recommended web sites I should visit to help me understand better ?
Havent cut any threads yet - still reading - does the answer become blindingly obvious after I have had a go ?
Bill
I see on the web that various other lathes have a similar plate.
What I dont understand is the assumptions behind the calculated values.
From what I have read, I currently think that the critical factors are
1. TPI on leadscrew
2. Number of teeth on stud gear
3. Number of teeth on final gear
4. Whether or not a compound gear is involved
5. Gearbox ratio (if you have a gearbox)
The way I see it, its reasonable to assume items 1, 2 and 5 were known by the people who calculated the values on the plate, (different values for item 2 are listed on the table)
They must have assumed something for items 3 and 4 ?
I've set up a spreadsheet for my lathe change gears and gearbox ratios and can calculate the TPI for various configurations and these calcs agree with VernonV's Latheworks program, so I think I understand the basic maths but I don't understand how anybody could print that plate without saying what they had assumed for items 3 and 4.
Any recommended web sites I should visit to help me understand better ?
Havent cut any threads yet - still reading - does the answer become blindingly obvious after I have had a go ?
Bill
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