Can someone help me wrap my head around all the divisions needed for a diving index?

I have no idea how I made the Dean's list and got awards for being smart....I feel like a kindergartener among you guys! The old saying, "if you don't use it you'll loose it" is for sure true. I couldn't pass a pre-algebra class now. I know that for a fact, I got out my old books because I was trying to figure something out and couldn't remember how to do it. I don't only couldn't do it, I couldn't even do some of the basics. When I was finished up with college and working in the field nobody wanted us to do algebra. They wanted us to draw the stuff and the computer would do the math and determine angles and sine bar heights. So, as it turned out, I only used algebra or trig ONCE in the years I worked in the field and the only reason I did it by hand then was because we didn't have a good piece of CAD software yet. Once we did it never happened again.

I just thought I'd drop that in there. Just because you're pretty sure you're never going to use higher math "in real life" there could very well come a time you wished you had kept up with it and could still use it. Some people just remember all that stuff. One of the first things I learned in engineering was NOT remember stuff that could be looked up. Now I wish I had remembered that stuff.

Wayne
 
G Jones said:
Id like to make a smal precision index that I can use to divide not only common gears, but pretty much any radius I really want. Its for dial indicators and eventually watches, so I'm not going to be sweating over primes, but I have this little itch after doing some quick memopad math, that I should be able to hit just about every degree or whatever up to a reasonably usable number with a minimal amount of drilled rings.
The 1./12 and 1/15 divisions should take care of all the smaller number sets, and then by having a larger clever ring or two, as well as an "offset" to slide between the 30 or 50 pin wheels, I feel like there is a way to make a maximum amount of gear patterns with a minimum number of holes.

I worry that this is actually getting into some pretty heavy theoretical maths, I have no Idea if anyone has figured this out before, and I don't know where I'd look to find papers on the subject anyways.

Its just a neat thought experiment. How can I make the maximum amount of variations with the smallest amount of hole sets. The answer lies in being able to offest the rings by fixed amounts to use them for more than one position. I jsut like thinking about this stuff, and its way cooler than spening a week CAREFULLY marking with dividers, drilling 500 holes, then reaming each one perfectly, only to slip up 90% percent of the way through and contemplate baking my head in the oven. (not serious)

EDIT: my dying stiff miserable keyboard is unreliable so I apologize for the constant egregious typos
EDIT NUMERO DOS; I mistyped radius a bunch as radians. screw radians. I aint got time for that **** and its not applicable to this in any way any how. RADIUS not RADIAN
Click to expand...
the easy is to buy a saw blade for vinyl siding 120 teeth that look like this vvvvv with a spring loaded indexer. no work with measuring or drilling. all it it needs is teeth counting and labeling
 
An additional solution worth looking at is one of the pre-made indexing plates from Alisam Engineering. They're designed to jam between the lathe spindle and chuck of a woodturning lathe. Pretty easy to adapt to a metal lathe - just enlarge the hole as needed, maybe mount to the outboard end of the spindle. They have one ring of 72 holes and another of 20. This will cover a wide range of divisions.

Alisam Engineering Universal Indexing Systems

Model WIS-1.0 and WIS-.75 Complete universal system for indexing on most 7 to 12 inch wood lathes
alisam.com
 
hman said:
hman said:
An additional solution worth looking at is one of the pre-made indexing plates from Alisam Engineering. They're designed to jam between the lathe spindle and chuck of a woodturning lathe. Pretty easy to adapt to a metal lathe - just enlarge the hole as needed, maybe mount to the outboard end of the spindle. They have one ring of 72 holes and another of 20. This will cover a wide range of divisions.

Alisam Engineering Universal Indexing Systems

Model WIS-1.0 and WIS-.75 Complete universal system for indexing on most 7 to 12 inch wood lathes
alisam.com
Click to expand...


the easy is to buy a saw blade for vinyl siding 120 teeth that look like this vvvvv with a spring loaded indexer. no work with measuring or drilling. all it it needs is teeth counting and labeling
An additional solution worth looking at is one of the pre-made indexing plates from Alisam Engineering. They're designed to jam between the lathe spindle and chuck of a woodturning lathe. Pretty easy to adapt to a metal lathe - just enlarge the hole as needed, maybe mount to the outboard end of the spindle. They have one ring of 72 holes and another of 20. This will cover a wide range of divisions.

Alisam Engineering Universal Indexing Systems

Model WIS-1.0 and WIS-.75 Complete universal system for indexing on most 7 to 12 inch wood lathes
alisam.com
Click to expand...
chatter chatter cut cut said:
the easy is to buy a saw blade for vinyl siding 120 teeth that look like this vvvvv with a spring loaded indexer. no work with measuring or drilling. all it it needs is teeth counting and labeling
Click to expand...
 
more on the saw blade for dividing head. made a internal expanding shaft to fit quill, mounted outboard with saw blade attached and spring loaded latch to hold. the different divisions are marked with different colored inkmarker. if you want a pic i will post one or private email.
 
I had a math minor in college, 4 semesters of calc. All long since washed overboard. I still use basic trig. Spread sheets are great for a lot of things.
 
My father was a "book keeper", not to be confused with an accountant. When I was in grammar school struggling with fractions, he taught me to convert to decimals, do the calculations and then grab an answer close to the decimal solution. I didn't learn fractions very well, but got by on the tests. I finally learned fractions on a B&S index head, where decimals wouldn't work. It had to be fractions. Although I never did fractions, I did understand trigonometry, both for electrical and celestial navigation. And used them repeatedly as I aged. If I had gone to high school, I would probably still be confused.

In answer to the original question, a dividing head is the nominal answer. I have a couple of rotary tables that would be small enough for many smaller projects. Nominal size 3 inch table. One has fraction plates so can be used as a dividing head. With a ratio of 72 rather than 40, many odd numbers can be acheived. Excepting primes, as noted above.

A smaller yet version can be, and has been, built using a small worm and wheel. A lot of work but then that's what we specialize at. Making tools to make yet more tools. I have not built a small dividing head but have seen many uTube videos of such being built. One specifically by an amateur watch builder, by the way. If a suitable worm wheel could be found, fraction plates can be easily developed by hand, with sufficient accuracy to be usable the first generation. Second generation plates have sufficient accuracy for any but NBS use. Mr Pete 222 goes into considerable detail on this subject.

EDIT: Added one of many links:

Fraction plates can be developed for most any prime number, again by hand. Although the higher numbers would make the fraction plate so large as to be essentially useless. All that is necessary is basic geometry and primitive drafting equipment. And a lot of time. . .

.
 
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A couple of years ago when I first bought my lathe I also bought a small divider. It has a ratio of 90:1. I didn't know at the time that 40:1 is more common. So I'm not sure how useful the 90:1 will be. Any one know if it's good, bad or doesn't matter?
 
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