Cutting splines questions

[markba633csi]

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

 

[Weldingrod1]

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

 

[rabler]

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.

 

[Lo-Fi]

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.

 

[macardoso]

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.

 

[Suzuki4evr]

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.

 

[Suzuki4evr]

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.

 

[Suzuki4evr]

Hi Michael,

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



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.

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.

 

[Suzuki4evr]

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.

 

[macardoso]

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.