Mike Pung originally posted this note in the Google group.
Crank Handle Indexing.
There are quite a few times that we need an index count that we may not
own. This is not a problem, all you have to do is look at the pitches
that you are capable of. Then go with what you know.
1. Every crank of the handle is going to send the carriage down the
rails 1/4"
2. When you are on a set pitch you will need "X" number of turns to
make the wood stock rotate once.
Lets see what this will do for us
1" pitch = 4 turns to rotate once
4" pitch = 16 turns to rotate once
6" pitch = 24 turns to rotate once
See what is happening?
One crank on a 6" pitch will rotate the stock 1/24th of an inch. If
you
rotate once and cut 24 times you will have a perfect 24 indexed flute or
bead.
2 will be 1/12th rotation 3 will be 1/8th rotation
Just use your gear sets
that you have and apply the math.
Here is a fun one
2X gear on a 15 pitch = 60 rotations
or 60 indexes
If you would turn 1/2 turn and run the router it would be a 120 indexed
project
need 40 indexes? 60 divided by 40 = 1.5 That's right turn 1 and
a half
cranks and run the cut.
Well hopefully I have yammered on long enough to get you thinking.
Mike
I spent some time exploring this option, and here's a summary of the results using the standard gear set that I have found.
| Number of Indexes Per Handle Turn | |||||||
|---|---|---|---|---|---|---|---|
| Gear | Pitch | 1/4 Crank | 1/2 Crank | 1 Crank | 2 Cranks | 3 Cranks | 4 Cranks |
| A | 2" | 24 | 16 | 8 | 4 | - | 2 |
| B | 3" | 36 | 24 | 12 | 6 | 4 | 3 |
| C | 4" | 48 | 32 | 16 | 8 | - | 4 |
| D | 4.5" | 54 | 36 | 18 | 9 | 6 | - |
| E | 5" | 60 | 40 | 20 | 10 | - | 5 |
| F | 6" | 72 | 48 | 24 | 12 | 8 | 6 |
| G | 7.5" | 90 | 60 | 30 | 15 | - | - |
Total index positions available: 23
2,3,4,5,6,8,9,10,12,15,16,18,20,24,30,32,36,40,48,54,60,72,90
If you own a 2X multiplier gear set will gain you a few more unique indexes.
| Number of Indexes Per Handle Turn | |||||||
|---|---|---|---|---|---|---|---|
| Gear | Pitch | 1/4 Crank | 1/2 Crank | 1 Crank | 2 Cranks | 3 Cranks | 4 Cranks |
| C | 8" | 96 | 64 | 32 | 16 | - | 8 |
| D | 9" | 108 | 72 | 36 | 18 | 12 | 9 |
| E | 10" | 120 | 80 | 40 | 20 | - | - |
| F | 12" | 144 | 96 | 48 | 24 | 16 | 12 |
| G | 15" | 180 | 120 | 60 | 30 | 20 | 15 |
Total additional unique indexes: 7
64,80,96,108,120,144,180
The .25 reduction gear set yields no further unique index positions.
These numbers are easily calculated.
No. of Cranks = Pitch / .25
Degrees = 360 / Cranks
Divide the travel of each gear by the pitch of the lead screw. In our case, The "A" gear travels 2". Our lead screw pitch is .25. So, 2 / .25 = 8 cranks to turn the spindle one time. 360º divided by the number of cranks calculates the incremental degrees for each crank. So, 360 / 8 = 45º. Here's a simple chart of the results.
| Gear | Pitch | No. of Cranks | Degree | ||||
|---|---|---|---|---|---|---|---|
| A | 2" | 8 | 45 | ||||
| B | 3" | 12 | 30 | ||||
| C | 4" | 16 | 22.5 | ||||
| D | 4.5" | 18 | 20 | ||||
| E | 5" | 20 | 18 | ||||
| F | 6" | 24 | 15 | ||||
| G | 7.5" | 30 | 12 | ||||
Working the numbers backwards, it's possible to take the desired degree and determine the cranks needed. I will leave that up to you.
Mike's system is ingenuous. A little imagination and math goes a long ways. The number of indexes listed by no means cover all of the possibilities. It's intended to be a quick reference. By altering the crank rotations many index locations can be accomplished without purchasing any additional index plates.
Mike also brought up the idea of using crank handle indexing with the rotary
table. It is possible, but could be considered time consuming and error prone.
See why in this Crank Handle Indexing
for the Rotary Table article.
Questions or comments, please feel free to contact me - Tim
Updated: 6/27/2010