Proxxon UT 400 Bedienungsanleitung Seite 6

5 Index plates
The dividing head comes with 4 interchangeable index
plates, one of which is already pre-mounted:
Each of them has 2 concentric bolt circles with a different
number of holes, which means that the division of the pitch
circles is also different.
Given that each index plate, as mentioned above, has 2 dif-
ferently divided bolt circles, a total of 8 possible divisions
are available. The number of holes is stamped on the front
of the index plates. The following text provides information
on the meaning and correct use of the index plates.
6 Important and useful basics
The division of a circle with this device may seem relatively
complicated at fi rst, but it is not. Important to know:
THE WORM GEAR HAS A REDUCTION RATIO OF 1:40.
In other words: The crank must be turned 40 times until
the fl ange with its mounted clamping device (chuck) makes
exactly one revolution.
The required number of crankshaft revolutions is always
calculated using the following formula:
Gear reduction ratio
= Required crank revolutions
Required divisiong
For us this means:
A full revolution of the crank moves the fl ange by
360°/40=9°. Conversely, this means that in order to turn
the fl ange 1° further, we must turn the crank by a 1/9 revo-
lution.
1. Example
We want to establish a "20" division. "20 division" means
that we want to distribute 20 form elements (e.g. holes)
with exactly the same spacing on a full circle. This of course
requires that one full revolution of the fl ange, or work piece,
is divided into 20 individual steps.
That means: 360° degrees divided by 20 steps equals 18°
per step! Based on the equation presented above, we cal-
culate:
40 = 2 crank revolutions
20
This means that if we make two revolutions of the crank,
the fl ange, or the chuck, will turn further by exactly 18°,
i.e. the required amount: As we have just seen, if the fl ange
rotates 9° per crank revolution, this results in 2 times
9° = 18° for 2 full revolutions, i.e. exactly our "division
step" calculated above.
But it doesn't always work out smoothly, as in this example.
A division of 15 would look like this:
– 10 –
2. Example
We now want to create a "15" division, i.e. fi ll a full circle
with 15 shape elements, e.g. drill holes on a bolt circle.
For a 15 division, one step by which the fl ange contin-
ues to turn further per "machining process" is 360°/15
steps=24°/step.
If we calculate again with the new values and the known
formula, we fi nd that we do not need an integral number of
crank revolutions with the crank ratio of 1:40:
40 = 2,666 crank revolutions
15
Because of the "odd" remainder, we now must choose a
suitable index plate whose number of holes and the result-
ing division can "reproduce" our desired rotation angle.
There is a selection table in the appendix for this purpose,
which helps us to easily fi nd the index plate required for
our division.
The respective columns and lines of the table have the fol-
lowing meaning:
7 Meaning of the values in the selection table
for the index plate
Column a: (required) division to be performed
Column b: corresponding "increment" in degrees (360°
divided by the division)
Column c: required number of "full" crank revolutions
Column d: additional holes required for performing
the required division (with different index
plates).
The various specifi cations from column d are also assigned
to the possible index plates: It is quite possible to achieve
the required crank angle by using different index plates with
different numbers of holes: The required identical angle can
be formed with different divisions of the index plate, each
with a different number of holes.
So in our column a we look for the value for the required
division, i.e. "15". In the corresponding row, the adjacent
column gives us the value of the degree steps, namely 24°
per step. Next to it is "2", which means "2 full revolutions",
plus (also next to it) 18 holes on the 27 disc (18 "additional"
holes divided by 27 holes equals 0.6666, which, according
to the calculation above, is the value we are missing for the
two full revolutions, taking into account the fl ange ratio to
our required step size!)
Or, put another way:
3 holes on the 27 perforated disc correspond to 1/9 turn
of the crank (i.e. one degree of the fl ange, as 40x9=360,
see above). 1/15 division corresponds to 24 degrees
(15x24=360 degrees). So we have to turn the crank 24/9
times. Meaning, 2 full revolutions and 18 holes on the disc
with 27 division.