# Cutting splines questions



## Suzuki4evr (Apr 16, 2021)

Hi guys.
Gears I've made,but now I must machine splines on a shaft for a hydraulic pump. #1.Do you need a spline cutter like a gear cutter?
#2. Or can you make a single point HSS cuuter.
#3.How do you calculate the angle of the spline
#4. How do you calculate depth of cut,does it work the same as gears?







The angle looks about 45degr.


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## Lo-Fi (Apr 16, 2021)

I have to admit to eyeballing it...  Worked out great!


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## machPete99 (Apr 16, 2021)

I have not done it but these are typically cut with a special cutter and a dividing head.
There are at least 2 types of forms: involute and straight.
From the looks yours appears to be involute and would require a special cutter to do properly.

EDIT: TOT has a video on doing straight splines, here:


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## Lo-Fi (Apr 16, 2021)

If I did it now, I'd do on the mill with rotary table and quill as Joe Pie often does. But I didn't have a mill back then!


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## brino (Apr 16, 2021)

Hi Michael,

My only spline project was posted here:
https://www.hobby-machinist.com/threads/my-first-and-second-attempt-at-cutting-splines.83187/



Suzuki4evr said:


> #1.Do you need a spline cutter like a gear cutter?
> #2. Or can you make a single point HSS cuuter.
> #3.How do you calculate the angle of the spline
> #4. How do you calculate depth of cut,does it work the same as gears?



I was lucky, I had printed specs. on the spline I was cutting.
(That meant I could look up a number of things in the Machinery's Handbook.)
Mine required a square 90 degree cutter, and I had one already.

I would think that a single point HSS cutter would work fine....I have seen that method used for gears and it worked there.
Just note that the cutter shape may change with spline size, just as in gears.
If you are copying a spline in the exact same size, then you should be able to grind the cutter to fit the existing one.

As for depth of cut I used the formulas in the Machinery's Handbook to calculate i) what gauge pins to use, and ii) the measurement over those gauge-pins. Obviously, this method requires two gauge pins of the required size, and an "even number" spline in order to have the gauge pins sit 180 degrees from each-other.

I hope you keep posting about your project.
It would help us all improve!

Thanks,
-brino

EDIT: the one thing that I should emphasize from my thread above was just how useful an aluminum test part was _before_ doing the real part.


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## BladesIIB (Apr 16, 2021)

I have cut them on the vertical mill with a dividing head and a single HSS cutter on the side. Looks like you have a good sample to work from. The spline closest to the shaft should have no wear and give you a good reference to fit your tool and measure depth. Depending on the tolerance you need that may work if you can’t find the cutter or get one in time.


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## Lo-Fi (Apr 16, 2021)

Wait, are you trying to cut a new shaft, or internal splines in the gears to fit that shaft?


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## jwmelvin (Apr 16, 2021)

It seems that splines commonly have an involute form and Machinery’s Handbook has 20 pages on the imperial involute splines. It also has this on milling cutters:


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## macardoso (Apr 16, 2021)

Did an internship in a gear/spline shop. Gives me the right to say I know absolutely jack s*** about gear and spline cutting lol.

Splines are typically parallel sided (as shown in the MH except above) or involute (what I am guessing yours are).

Both types are production cut with hobs on a gear hobber or with milling cutters in lesser production runs.

The involute spline *should* be able to be cut using the standard involute gear milling cutters. Trick is identifying the specification to which the original spline was cut. Critical parameters are imperial/metric, Diametral Pitch/Module, pressure angle, and pitch diameter (measurement over wires). There are also lots of modifications to the standard profile such as truncated addendum/dedendum, flat/radius root, truncated crest, corner chamfers, etc.

A parallel sided spline can be cut using a parallel spline milling cutter (again shown in the MH except above) or approximated using endmills and an indexing head.

If you were able to determine the diametral pitch/module (can be calculated from the number of teeth and the size of the shaft) and the pressure angle (trickier, typically 30 degrees) then you can match the cut using measurements over thread wires stuck in the teeth. Even numbered teeth on the shaft are easy, odd numbered needs a bit of trig to calculate the PD.


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## rabler (Apr 16, 2021)

Looking closely at the end of the splines, where the diameter of the shaft increases not the end of the shaft, I would say that is a straight trapezoidal cut.  But I'm certainly just going by what I see ...


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## markba633csi (Apr 16, 2021)

Going by the picture, it looks like at the root of the splines it's so narrow you could effectively consider it flat so it would be fairly easy to grind an HSS tool to a close replica of the spline shape
-Mark


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## Weldingrod1 (Apr 16, 2021)

Hydraulic pump splines are involute. A little surfing should get you the SAE spline type and the dimensions. You should use good steel if you are working it even moderately hard. 4140, 4130, or 4340 commercial heat treat would be a good start. 

CRITICAL: lube your splines!!! You need a 50%+ MoS2 content lube if it's not running in an oil bath!! You WILL be appalled at the cost of what you need for this. If you aren't, you don't have the right stuff ;-) Honda M77 moly paste is easy to get and has enough moly content to be useful.

Sent from my SM-G892A using Tapatalk


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## rabler (Apr 16, 2021)

Weldingrod1 said:


> Hydraulic pump splines are involute.


I'm asking because I'm uncertain, trying to learn:

Are these splines actually part of the fluid pumping component in a gear pump, or are they a male shaft that couples to a female splined component just to transfer rotary power?  Seems to me that a coupling with involute cut splines would be totally unnecessary, all you need for splines is flat mating faces, so why get fancy (KIS)?   I can understand why a gear-pump would need involute gears in the pump.


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## Lo-Fi (Apr 16, 2021)

They're for mechanical coupling. To expand: they're likely hobbed during manufacture, same as gears. Hobbing naturally produces involutes, so they're actually easier to make that way. There are all manner of standards, most of which are not accessible to the hobbyist. Within those there are variations on flank profiles, centering arrangements and all sorts of spline related shenanigans. Went down that rabbit hole myself!! 
Unless it's a high speed application, make your best guess. If you've got the gear, make a broach from tool steel using an involute cutter or just single point it.


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## macardoso (Apr 16, 2021)

rabler said:


> I'm asking because I'm uncertain, trying to learn:
> 
> Are these splines actually part of the fluid pumping component in a gear pump, or are they a male shaft that couples to a female splined component just to transfer rotary power?  Seems to me that a coupling with involute cut splines would be totally unnecessary, all you need for splines is flat mating faces, so why get fancy (KIS)?   I can understand why a gear-pump would need involute gears in the pump.



The involute spline is extremely common in many applications. The benefit is that they are stronger than straight sided splines and are easier to cut and fit. Production of splines is a commercial process which is done typically with a hob. 

So yes, any form of mating M/F spline will work, but the industry has settled on involute and a specific form of the parallel sided spline.


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## Suzuki4evr (Apr 16, 2021)

machPete99 said:


> I have not done it but these are typically cut with a special cutter and a dividing head.
> There are at least 2 types of forms: involute and straight.
> From the looks yours appears to be involute and would require a special cutter to do properly.
> 
> EDIT: TOT has a video on doing straight splines, here:


I seen this video twice I think, but those splines are more PTO size and my part has very fine splines.


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## Suzuki4evr (Apr 16, 2021)

Lo-Fi said:


> If I did it now, I'd do on the mill with rotary table and quill as Joe Pie often does. But I didn't have a mill back then!


I will be doing it with my dividing head on the mill.


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## Suzuki4evr (Apr 16, 2021)

brino said:


> Hi Michael,
> 
> My only spline project was posted here:
> https://www.hobby-machinist.com/threads/my-first-and-second-attempt-at-cutting-splines.83187/
> ...


Hi Brino.
I checked out your post and I too thought of doing a aluminium test piece first. But my first priority is to sort out the cutter. Unfortunately I am not as lucky to have a cutter in my arsenal.


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## Suzuki4evr (Apr 16, 2021)

Lo-Fi said:


> Wait, are you trying to cut a new shaft, or internal splines in the gears to fit that shaft?


I am making a new shaft. Apparently these shafts are not available after market,the client must buy a new pump every time.I will be making a few in future. My client asked me long ago if I able to make them,but back then I did not have a dividing head or any clue to use it. Things changed in the meantime.


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## macardoso (Apr 16, 2021)

Suzuki4evr said:


> I am making a new shaft. Apparently these shafts are not available after market,the client must buy a new pump every time.I will be making a few in future. My client asked me long ago if I able to make them,but back then I did not have a dividing head or any clue to use it. Things changed in the meantime.



In this case, investing in the right cutter for the job will probably pay off.


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## Suzuki4evr (Apr 16, 2021)

jwmelvin said:


> It seems that splines commonly have an involute form and Machinery’s Handbook has 20 pages on the imperial involute splines. It also has this on milling cutters:


Will jump on that on Monday. Thanks.


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## Suzuki4evr (Apr 16, 2021)

macardoso said:


> In this case, investing in the right cutter for the job will probably pay off.


You might have a point. I will do some homework on Monday and surf on eBay. Bought gear cutters there before and they were pretty decent.


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## aliva (Apr 16, 2021)

Keith Rucker has a video


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## Suzuki4evr (Apr 16, 2021)

aliva said:


> Keith Rucker has a video


I will have a look. Thanks


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