Rotary table project

[Bob Korves]

I would just go with 90 teeth, like on many commercial models. Then you can divide the four degree (240 minutes) revolution of the worm up more easily.

 

[mickri]

I must be missing something because I can't for the life of me see any advantage to using degrees and minutes. How do you mark the handwheel dial? Do you divide it into 240 parts? I think that I will go with a 72 tooth worm gear because using tenths of a degree and 5 degree increments is easier for me than trying to deal with degrees and minutes.

 

[Bob Korves]

I must be missing something because I can't for the life of me see any advantage to using degrees and minutes. How do you mark the handwheel dial? Do you divide it into 240 parts? I think that I will go with a 72 tooth worm gear because using tenths of a degree and 5 degree increments is easier for me than trying to deal with degrees and minutes.

In that case you are starting to talk dividing head rather than rotary table, which is fine, just different. Dividing heads divide evenly, Rotary tables dial in degrees, minutes, and seconds as desired. Some rotary tables are equipped with dividing plates on the worm shaft, which also make them useful for dividing.

 

[mickri]

Dividing a portion of a degree into minutes and seconds is just too easy to make mistakes. You are using what I may wrongfully call a base of 60 for calculations. Much easier to use a base of 10, 100 or 1,000. What I call decimal degrees. It is a term from navigation for boats where you use degrees and decimals of a degree instead of degrees, minutes and seconds. Came about with the use of a gps for navigation. For example 51.456 degrees is the same as 51 degrees 27 minutes 21.6 seconds. Either has the same precision. Decimal degrees is just easier to use for me.

 

[Bob Korves]

Nomenclature is not a big issue. What matters is what it is going to be used for. If you are making a gear that is 41 teeth, you want to divide it evenly, and not chase it inaccurately with a dial and risk making mistakes. Like you said, that can get confusing quickly, regardless of decimal or degree, minute, seconds. And it won't come out even anyway, unless you have a 41 tooth table drive or some multiple thereof. If you are trying to accurately mill an arced slot on a metal plate that needs to have a 78.12 degree included angle, then a dividing system is not really very useful. Dividing and angle measuring tools are for different types of work.

 

[mickri]

Attached is an expanded rough sketch of the table. Hoping to get by a metal supply tomorrow to get some materials for this project and others. My question is how thick should the base be? 1/4", 3/8", 1/2", or ????