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Hobby Engineering · Machining · Planner
Dividing head indexing planner
Work out direct, simple, and compound indexing setups from your dividing-head ratio and indexing plates, then see when an awkward division count needs an approximation or a more advanced differential setup.
What this page is for
- Find out whether a division count can be done by direct indexing, plain simple indexing, or compound motion across two circles.
- See multiple exact setups instead of stopping at the first chart entry.
- Judge approximation quality by spindle-angle closure error instead of guessing from a crank fraction.
- Spot jobs that are really asking for differential indexing or a different machine.
Required movement
Exact indexing options
Best approximation if exact indexing fails
Practical notes
Indexing methods in plain English
- Direct indexing locks straight into a hole plate on the spindle. It is quick, but only supports counts that divide that plate.
- Simple indexing turns the crank by whole turns plus a hole count on one circle.
- Compound indexing combines movements from two circles when one circle alone cannot hit the fraction exactly.
- Differential indexing moves the plate while you crank. Use it when the page says no exact direct/simple/compound answer exists.
Typical hobby-engineering jobs
- Gear tooth counts that do not sit on the obvious divisors of 40.
- Bolt circles, spoked wheels, evenly fluted cutters, and polygon work on manual mills.
- Checking whether a tempting near miss is actually safe over a full revolution.
- Understanding whether your current plates are the limiting factor before buying more tooling.
Common questions
What if my dividing head cannot cut the exact number of divisions I need?
The planner shows when direct, simple, or compound indexing is exact and when you are only getting an approximation, so you can decide whether the error is acceptable before cutting metal.
What is the difference between simple and compound indexing?
Simple indexing uses one hole circle for the crank movement. Compound indexing combines two circle movements to hit counts that one circle alone cannot represent exactly.
Can this help with bolt circles as well as gears?
Yes. Any job that needs equal divisions around a full turn can use the same indexing logic, including bolt circles, flutes, splines, and regular flats.