awake
Titanium
- Joined
- Jan 24, 2006
- Location
- Angier, North Carolina
I have seen mention of some lathes that, in addition to tpi and metric threads, cut diametral pitch and modulus "threads." I'd like to learn more about this, so if anyone can answer some questions, I would be most grateful!
1) I am thinking that these would be used to cut a hob -- yes? No?
2) If I have done the math right (which is a big if!) then these "threads" would need to include a factor of PI. For example, modulus 1 gears have a circular pitch of PI mm (again, assuming my math is correct ...), so I'm thinking that the hob would need to have threads of 3.1415926 mm pitch. If I'm right about question # 1, then lathes that can cut a modulus 1 "thread" would be cutting 3.1415926 mm threads. Yes? No?
3) If I am right about question # 2, then what sort of gear train is used to generate these "threads"? Since PI is not a rational number, it can only be an approximation. 22/7 gives an approximation with an error of a little over .04% but to get much better than that, it looks like you have to go all the way up to 201/64. Is this the sort of gear ratio that is used, or am I missing some really easy way to get PI into the gear train?
Thanks for any help!
Andy
1) I am thinking that these would be used to cut a hob -- yes? No?
2) If I have done the math right (which is a big if!) then these "threads" would need to include a factor of PI. For example, modulus 1 gears have a circular pitch of PI mm (again, assuming my math is correct ...), so I'm thinking that the hob would need to have threads of 3.1415926 mm pitch. If I'm right about question # 1, then lathes that can cut a modulus 1 "thread" would be cutting 3.1415926 mm threads. Yes? No?
3) If I am right about question # 2, then what sort of gear train is used to generate these "threads"? Since PI is not a rational number, it can only be an approximation. 22/7 gives an approximation with an error of a little over .04% but to get much better than that, it looks like you have to go all the way up to 201/64. Is this the sort of gear ratio that is used, or am I missing some really easy way to get PI into the gear train?
Thanks for any help!
Andy