# My first (and second) attempt at cutting splines.........



## brino (Mar 23, 2020)

Hi everyone,

I have a friend that is very heavy into building electric cars.
Several years ago he converted a regular, gas-powered Toyota Echo to electric.
I helped build a new plate to bolt onto the front of the transmission to mount the single big DC motor.
I also built the motor shaft to transmission input shaft coupler.
He added banks of batteries under the hood, and in the back.
He still has that car running, but now he wants to build something better.

The technology is moving along fast.
He has already bought some motors, and a replacement battery pack from a commercial electric car (I forget which one....).
He has them all on his heavy-duty work bench getting ready for testing.
He wants to connect two of these motors "face-to-face" so that he can load one with the other for testing.
That means he needs a double-ended splined shaft.

He has four Yasa P400RS motors. They are liquid cooled, high-efficiency, high-torque, high-voltage, 3-phase DC motors.
https://www.yasa.com/wp-content/uploads/2018/01/YASA_P400_Product_Sheet.pdf

I had never cut a spline before, but once he found the spec. for what he needed and I had a chance to go thru the Machinery Handbook section and run some numbers I decided to give it a try!

First, I made a test spline from aluminum.
Since I needed to turn down some oversize stock on the lathe before moving to the mill, I thought I could use the same chuck on the lathe as on the rotary table on the mill. I did NOT have long piece of aluminum bar the proper diameter, so I drilled, tapped and connected a smaller bar to the end of the large stock to use as a handle. They were assembled with threaded rod and thread-locker. Since I needed to turn down the ID of the larger piece, it should end up concentric anyway.

Here it is with the smaller bar held in the collet chuck on the lathe and the OD being sized:



When that was done, the work-piece was left in the chuck and the entire thing moved over to the mill:



Unfortunately, I did not (at the time) have a proper height tailstock to match the rotary table.
What I used was a centre I turned on the lathe, held in a 5C-collet, in a spindexer, up on 1-2-3 block stilts:


(you cannot see them, but there's also some parallels laying flat between the 1-2-3 blocks and the spindexer)

Here is cutting a spline (or is it a groove between splines.......)



I tried multiple times to upload a video of cutting a spline,
I will try again in a new post...stay tuned.

-brino


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## brino (Mar 23, 2020)

I still cannot get the video to work, even after "smalling it down" a bit.........

Here's some other stuff instead......

Some close-ups of spline #1, the aluminum test spline:






Yes there is some slight surface irregularity, I think I may have a slightly bent feed shaft....but that's a problem for when I retire and have more than a few hours back-to-back to deal with it. Besides the mill is already 104 years old....I'd be complaining too!







I have more to post, but I am expecting the "dinner bell" any minute now.
I will try to post more later today!

-brino


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## Aukai (Mar 23, 2020)

I would like to be able to do 10, 18, and 26 splines. Thanks for posting.


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## Lo-Fi (Mar 23, 2020)

YouTube for uploading the video! Fantastic work and a really cool project that's it's for too.


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## epanzella (Mar 23, 2020)

That looks AWESOME, Brino!


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## Janderso (Mar 23, 2020)

I'm certainly impressed.
Well done sir, especially for a rookie.


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## DavidR8 (Mar 23, 2020)

Wow, that's some darn impressive work!


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## brino (Mar 23, 2020)

Here's a few shots of my rotary table......(but don't look at the work it's holding some shots are from spline #2, the steel one.......)

I need a 32-tooth spline. I have a 90:1 rotary table, and there were multiple plates to get me there.

So 90:1 gives 360/90 = 4 degrees on the output shaft for every full turn of the handle.
And 360/32 = 11.25 degrees per spline.
Since two full turns gives 8 degrees, I still need 11.25-8 = 3.25 degrees.
Given 3.25/4 just multiply top and bottom x 4/4 = 13/16.

I could also have used :
2 full turns and 52 holes on the 64-hole plate, or
2 full turns and 26 holes on the 32-hole plate.

I chose the 16 hole plate, so I need two full turns and 13 holes on the 16-hole plate.
I set the sector arms(checked my counting twice!) to reduce errors.










back with more later.....

-brino


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## Janderso (Mar 23, 2020)

Nice RT.


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## brino (Mar 23, 2020)

I tried again to down-size the video, hopefully the quality doesn't suffer too much.....

There is some extra sound due to pushing some other garage stuff back so far that the mill motor bracket is vibrating on it.
....of course there is also some wear in the vertical head.

-brino

View attachment spline1c.mp4


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## brino (Mar 23, 2020)

Okay, I had a problem with the first spline.....good thing it was just my test piece.......

Measuring for proper depth of cut of a spline is done by holding specific size gauge pins in two opposite grooves and measuring over them; like measuring threads with wires.

My measurements showed is was a little big, and tapered.....more than I had hoped. My target was 1.465"
When I checked my aluminum test part I measured 1.466" at one end and about 1.476 on the other (over the two 0.080" gauge pins).
The splined section is only ~3 inches long.

The bad news is that the small end was towards the "handle end" so it could not even be tested in the motor female spline.
No problem, just whack it off and re-chamfer.
I even stamped the measurements on either end and it became our "spline gauge".







My friend found that it did mate....for about an inch, and then got tight.

This piece was not long enough, or strong enough to be used for the end purpose.
But as a test vehicle, I considered that a success!

-brino


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## Lo-Fi (Mar 23, 2020)

So you need a better way of tramming your rotary table in and you're probably good to go. I'll look forward to the next installment


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## finsruskw (Mar 23, 2020)

AWESOME!!!
I swear, you guys are LIGHT YEARS ahead of me for sure.
And to think my cutting a keyway yesterday was a big deal!!
At least my hat fits better now


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## brino (Mar 23, 2020)

Okay, where did those errors slip in?

1) I measured it coming off the lathe and already had some taper there.
2) I made a mistake in mounting to the mill....but I figured it out and have learned from it......

Here's the mistake:
When I first moved the part from the lathe to the mill, I still needed to bolt-down the rotary table and the tail-stock support.
I finger tightened the rotary table clamps, and lined up the tailstock loosely.
I put an indicator in the spindle and ran it across the front of the part, slowly fixing the angle and tightening down.
I still believe I had the front edge straight with the table and x-axis.
....but then, *I cut the grooves on the backside of the part!*

Because of that existing taper, the backside of the part was NOT aligned with the table x-axis.
That would make the splines tapered too; cut deeper at one end than the other!

I can do better!

-brino


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## brino (Mar 23, 2020)

Okay here's some info/shots of the cutting tool I used.
I do NOT know where I got it....It might have come with the mill tooling, or it might have been from the local new/used tool store.

The cutter is a 90 degrees included angle and is about 2-3/4" diameter. It is HSS with a 1" hole.

I mounted it on an arbour and mounted that into a 1" end-mill holder that matches my mills' #11 B&S taper.










still more to come........

-brino


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## horty (Mar 23, 2020)

Brino, I'd sure like to give you some advice on something, but I have none. 

You Do Great Work..


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## brino (Mar 23, 2020)

Alright! Before starting the real long, steel spline I needed to upgrade a couple things......

1) Since this part is going to be about 12" long (~4.5" of spline at each end) I needed a lathe steady rest to hold it while I added centre holes.
2) I needed a better tail-stock to match my rotary table.

Sure I could build them, but I want to do these other projects more......
For the steady rest I found a used on on ebay, that looked about right. It fit the bed fine, but turned out to be from a 10" lathe so the centre height was a little off. I solved that with some "offset fingers".

I found this tailstock at my local used tool store. It needed a little work:

the centre was cut/drilled and needed to be cleaned up, and 
I had to take about 50thou off the casting to allow the adjustable centre to go just a smidge lower.....




For raw stock, I found some 1.375" steel shaft, that had the perfect starting OD.

The first few grooves go very slow.  I wanted to cut in two passes to full depth. 
Obviously, to get a measurement I need to cut one groove and then crank the handle 45 turns and cut another. 
Only then can you measure it while juggling the two gauge pins and the micrometer.....
I did a few of those to help dial in the depth of cuts.
I found a combination that seemed to measure perfectly (first pass depth 25 thou, second pass depth 38 thou.)








View attachment spline2_front.mp4


















View attachment spline2_back.mp4


















I have one more video I'll try in the next update......

-brino


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## DavidR8 (Mar 23, 2020)

That there is some serious knurling! 


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## Aukai (Mar 23, 2020)

Learning a lot, I guess the key way is not needed, I have an arbor without also.


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## brino (Mar 23, 2020)

Here's a few shots of the long (~4.5 inch) steel spline on the 12" shaft....one end done, now (after test fit) I just gotta do it all again!

The reduced end is for mounting an rpm indicator for bench testing.









Still trying to cut down one more video...it may not be available tonight.

-brino


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## brino (Mar 23, 2020)

Oh, and how did I do on the second one?
Target is 1.465"

right at the end: 1.465"



another groove, and down a bit: 1.464"



That's why I build test parts for new (to me ) operations......

-brino


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## Dhal22 (Mar 24, 2020)

Awesome.


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## Aukai (Mar 24, 2020)

VERY impressive


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## Lo-Fi (Mar 24, 2020)

Loving your work!


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## ACHiPo (Mar 24, 2020)

Great job!


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## brino (Mar 24, 2020)

Thanks for the reads, thumbs, and feedback.

I could share some of the math used to calculate the depth of cut, if there is any interest.

-brino


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## brino (Mar 24, 2020)

Aukai said:


> I would like to be able to do 10, 18, and 26 splines.



You can do it too!
With a rotary table and plates, a proper tooth form cutter, a bit of research and a little bravery to jump in....

Much like gears, there are different "tooth" shapes, so you really need to know what specification to build to, especially if you need to interface with a part that someone else built.

Mine is an ANSI B92.1-1996, Fillet Root Side Fit.
32 teeth, spline pitch 24/48, with a 45 degree pressure angle.

Machinery's Handbook explains a lot, and I used a spreadsheet to help too.

-brino


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## rgray (Mar 24, 2020)

Are you going to case harden? Or are they good enough for what they will be used for?
Good job. They look great!


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## C-Bag (Mar 24, 2020)

I'm in awe Brino. I get you learn a lot when you go to do a project but WOW. 

Thanks for posting.


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## brino (Mar 24, 2020)

rgray said:


> Are you going to case harden? Or are they good enough for what they will be used for?
> Good job. They look great!



Thanks!
Since these are only for bench testing the motors we are hoping that they will prove strong enough without hardening.
Those motors sure have a lot of torque, but it is spread over all the teeth (unlike a gear).
The other part is that he should be in full control of how stressful the testing is, unless his control system starts doing full speed reversals......then we might have a problem.

I have wondered how case hardening would change the shaft.......I am NOT setup for finish grinding.

-brino


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## rgray (Mar 24, 2020)

brino said:


> I have wondered how case hardening would change the shaft.......I am NOT setup for finish grinding.



I also wondered about that. Maybe induction case hardening????
Maybe start with 41xx series prehard?
Splines like that have a large surface area so they are probably more than fine for what he wants to do with them.


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## DavidR8 (Mar 24, 2020)

I’m curious about how the matching splines are made on the input shaft. 
Some sort of V-shaped broach?


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## brino (Mar 24, 2020)

DavidR8 said:


> I’m curious about how the matching splines are made on the input shaft.
> Some sort of V-shaped broach?



Maybe rotary broach?
-brino


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## Lo-Fi (Mar 24, 2020)

If its a blind hole they'd most likely be made with a gear shaper. The tool itself is like a gear, but the teeth are cut with relief and has a few less teeth than the internal teeth you want to cut. It's used in a machine that rotates the work and cutter both geared such that tool and work spin at speeds as though they were meshing. The cutter is moved axially too and works like a rotary shaper tool. It's gradually in-fed radially until the full spline depth is formed. 

I see it done often, I work for an aerospace gear manufacturer. Through hole splines are usually broached, with the broach pulled through the work


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## brino (Mar 24, 2020)

Lo-Fi said:


> If its a blind hole they'd most likely be made with a gear shaper..........
> Through hole splines are usually broached, with the broach pulled through the work



Thanks @Lo-Fi, I have never seen it done in person.

In this case the motor holes are thru-holes.
The motors are actually built to be "stacked" on a long splined shaft, to parallel them.
The motor female spline is missing one gap in order to completely synchronize the stacked motor controllers.
-brino


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## rgray (Mar 24, 2020)

Lo-Fi said:


> The cutter is moved axially too and works like a rotary shaper tool



I've seen these cutters on ebay for next to nothing. Always thought I should get one and try it on my 100+ year old shaper.
I look at the pictures of those gear shapers though and get intimidated. They are huge and very rigid looking.
Plus it would take quite a bit of rigging to mount all that up on an old shaper.


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## Lo-Fi (Mar 24, 2020)

rgray said:


> I've seen these cutters on ebay for next to nothing. Always thought I should get one and try it on my 100+ year old shaper.
> I look at the pictures of those gear shapers though and get intimidated. They are huge and very rigid looking.
> Plus it would take quite a bit of rigging to mount all that up on an old shaper.



The tricky bit is rotating the cutter and the work simultaneously. If cutting involute teeth, it's the rotation of the work and cutter that are important for creating the involute profile, same as a hobb for external teeth. It's a fascinating subject.


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## graham-xrf (Mar 24, 2020)

One cannot help but be impressed. It's all just very, very good!
I even smile at "smalling it down" (the abortive video edit attempt), because you put the phrase in quotes.


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## benmychree (Dec 21, 2022)

My confusion regarding the cutter was due to the fact that it was not stated that you were cutting a SERRATED spline, I envisioned a straight sided (parallel) spline that has a flat root, or an INVOLUTE spline.


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