# Thread: 'simple' spline calculation help pls

1. ## 'simple' spline calculation help pls

Would someone be kind enough to point me to where I might be able to learn how to specify some simple splines?

Let me expand. I need to create a series of spindles for tap (faucet) cartridges (the ceramic disc types).

These have 'simple' splines. I have found out that they are 90 degs tween splines, triangular shaped (no curves or anything top or bottom).

I need 18, 20, 24 & 28 splines. I can replicate what I find on existing tap (faucet) cartridges but I have no idea how they are derived and I, because I'm like that, need to know - yes I am that sad! I understand there is something about using some theoretical 'pins' and I've seen some reference to that ont tinterweb but but butt...

A 'old moron's guide' would be greatly appreciated

2. Many thanks for those. I had found some not others.

Confession time. I can't make head nor tail of it all. From what I can see, that seems to be for 'proper' splines, splines designed to transmit power properly. Splines with reasonably complex curves rather than the simplistic straight sided things I need.

Unfortunately, I need a translator too as I no speakee formal/proper engineering! Any takers?

3. Knowing the spline angle helps significantly as does having straight sides. You also have an even number of splines in each case which make the measurement over pins much easier.

The pins are machinist's gauge pins. Pick two identical pins that will fit in the 90 degree vee and contact the flat sides of the spline, 180 degrees apart. Measure across the pins and use geometry or trig to describe the vee.

You can also ask your customer how they will be gauging the parts so you can agree on a method of inspection and tolerances.

4. Hi Hudson

Thank you so much.

I have managed to find DIN 5481 which kinda feels right. From further reading I understand one calculates the pin dia as it must touch at some 'magical' point (or the spline fairies get you...) which then gives a 'measurement over pins'.

However, what I cannot find anywhere is the formula for calculating all of this. Apparently DIN 5481 has angles of 45 & 60 but what I need is 90. From looking at things it seems one calculates and that delivers an overall dia and spline count (or have I got that wrong?). What I need is to match things so the calculation somehow has to be transposed and kind of worked backwards...

I see there is software to do this, but it seems complete overkill for 4 splined shafts; plus of course I'd have no idea what I was doing with it anyway

In terms of gauging, this is what this is needed for. The gauge suppliers are, lets just say, less than helpful! Basically don't want to know. If you know of any that are UK based and friendly/helpful then please feel free to let me know - I might get some sleep then .

5. The pin diameter for your 90 degree notch is not terribly important. You just need to know what the diameter is and what the overall measurement is. Pick a diameter that is perhaps just a bit less or the same as the distance between the top edges. You can repeat the measurements with pins just a bit smaller as a double check. The lay them out in a CAD program or on paper at some enlarged size and see what the pattern looks like when you add the balance of the grooves. With no involute shape to worry about it should be a simple geometry problem.