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# JIS D 2001 (1959) : 260x33x7.5

## JIS D 2001 (1959) : 260x33x7.5

(OP)
Hello All,

I'm looking to obtain internal spline data to match a certain external spec I've been given. Currently here are my know values;

JIS D 2001
260 Nominal
33 Teeth
7.5 Module
H9 / f10
Coefficient of Profile Shifting = +0.633
Pressure Angle = 20°
Basic Pitch Circle Diameter = 247.5
Class = b
Pin Diameter = 13.5
Measurement over pins = 274.717 / 274.564
Base Tangent Length @ 5 Teeth = 106.345 / 106.262
Major Shaft Diameter = 258.5
Minor Hole Diameter = 245

The internal values I'm after are;

Base Circle Diameter
Circular Thickness
Dimension between pins (13.5)

Any help would be greatly appreciated!! I've been trying to calculate these for awhile but the cant seem to make it match up.

### RE: JIS D 2001 (1959) : 260x33x7.5

I've never seen that standard, so I can only guess based on some other standards with a similar approach:
Base circle diameter: 232.574
Circular gap thickness: 15.237-15.280
Minor dia.: 245
Major dia.: 262.25
Dimension between pins Dk=13.5=236.030-236.140 (these pins need to be flattened .7 min.)
Dimension between pins Dk=15=230.162-230.288

### RE: JIS D 2001 (1959) : 260x33x7.5

(OP)

Question: I'm unfamiliar with the term "flattened" when describing a pin?

When determining the dimension between pins, are you using the valve a1? The equation I found is: inv * a1 = (sg - V ) / dg

I could not solve that equation to then plug and chug on the diameter between pins value.

Hopefully that makes sense! Thanks again Spigor, your replay has directed me in the right direction.

### RE: JIS D 2001 (1959) : 260x33x7.5

a flat is ground on wires to clear from interference at the root diameter of a spline.
if the wires bottom out (interferes) with the root diameter a false Measurement will be the results.

the base diameter is a simple calculation.
the knowns are
Number of teeth
diametral pitch or module
Pressure angle.

tons of free information out there to google.

the spline could be a special modification slightly off from the specification.

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