What's new
What's new

Help with Spline Cutting

adammil1

Titanium
Joined
Mar 12, 2001
Location
New Haven, CT
I need to make a splined shaft with matching splined parts in a limited machine shop;

The internal cutter seems rather easy to make. I will just create a broach holding tool roughly as follows, with a square key in the red zone and a slot for the broach at 60deg.
internal cutter.png
The male shaft is the one that I am scratching my head thinking of how best to do. I have an indexing head and via endmills I could carve out the teeth roughly as seen in the image below. But that leaves me with a flat portion. Where does the part rest on a spline, is the contact supposed to be solely on the keys, or on surface I will mill away? I doubt there's a cutter for doing this job is there? Is there any simple way for shop with out gear cutting equipment to make these?

The plans I have, tell you to mill a slot and silver solder in keystock. I am starting to think this maybe the best way to make these parts.
Male Shaft.png
 
If you mill the 0.33 wide slot with the end of an end mill, then you will get a flat bottom.
Ideally you need a form cutter, where you use the side of the cutter.
It is quite normal to grind a single point cutter out of a piece of HSS or a broken center drill or similar and use that as a fly cutter. Grind a tool to fit your profile with all the necessary clearance angles and rake, and make a simple arbor to put the tool in. Cut the splines one at a time using your dividing head.
Good learning exercise.
This link will help you.
Good luck,
Bob
 
If you cut both sides of the standing key with say an 1/8" endmill, you can make many passes rotatimg slightly between each pass and generate a cylindrical minor diameter.

Some straight splines are major diameter fits, some are minor diameter fits. Major dia fit must have a cylindrical major, and vise versa for minor diameter fit. If you are making both members take your pick.
 
If you cut both sides of the standing key with say an 1/8" endmill, you can make many passes rotatimg slightly between each pass and generate a cylindrical minor diameter.

Some straight splines are major diameter fits, some are minor diameter fits. Major dia fit must have a cylindrical major, and vise versa for minor diameter fit. If you are making both members take your pick.
That's an interesting thought on doing it with many passes on a 1/8" endmill.

As far as major vs minor dia fit you saw my picture of the tool I plan to use on the bore, basically a modified/custom broach bushing. If we're using the major diameter it would all be in contact with flat surfaces which would be unconventional but I think it would work. I will certainly play a little with some practice sets before I work on the real parts.
How

How limited is the question.
We're pretty much limited to the best 1975 had to offer with DROs. I have a nice lathe, mill, surface grinder, bench grinders. A CNC Prototrak type knee mill will be online and running later this year.

No gear cutting WEDM or anything fancy to make my own tooling. I wonder though if this is to be done with a fly cutter, how much would it cost to get something WEDM'ed up to do this perfectly?
 
If you mill the 0.33 wide slot with the end of an end mill, then you will get a flat bottom.
Ideally you need a form cutter, where you use the side of the cutter.
It is quite normal to grind a single point cutter out of a piece of HSS or a broken center drill or similar and use that as a fly cutter. Grind a tool to fit your profile with all the necessary clearance angles and rake, and make a simple arbor to put the tool in. Cut the splines one at a time using your dividing head.
Good learning exercise.
This link will help you.
Good luck,
Bob

I followed that link and it looks like the guy essentially made a dovetail cutter how does that get us to the profile of a spline such as the one shown in my image? I guess if I take a lot of little passes it may work. Maybe the more I think about it, just taking one of my dovetail cutters and going back and forth several times maybe enough. I only need one shaft with several matching gears running down the spline.
 
With the gear you have you could rough the shaft with a mill and then dress a surface grinder wheel to the correct profile and grind it. You ca also dress the wheel to grind a form cutter
 
When I needed a splined shaft, I had a local gear-making machine shop make it. No way would I have been able to create splines of acceptable quality.
 
I went through this whole process with a clients CY lathe which is a good quality Chinese lathe. Someone turned the shaft into a pretzel, they must have fed into the chuck with a super high federate. Eventually called them and asked if they could make it. They said no problem and then found a replacement in the store $100. When I received it the fit was perfect. I couldn’t do it for that. As a learning experience if you have the time and money this is a good job. If you’re trying to make money get the specialists to cut it.
 
The idea is to grind a tool that fits the profile of the spline. So the end of the tool needs to be 0.33" wide, with the corners not square, but at same angle as the side of the spline groove. The the end of the tool is not square, but has a curved profile that fits the root of the spline groove. You should be able to do this on a bench grinder by hand.
Mount this tool bit in an arbor - a piece of round bar with the appropriate hole and a grub screw to secure it.
The key then is the setup so that the tool bit is on the centerline of the job. Cut one spline at a time, index the required degrees, and do it again. Do a test sample to get your set up correct, and go for it.
This a way to do this job, if you are prepared to put the time and effort in.
This is the traditional way to make a spline or even a spur gear, the difference here is that you make your own tool rather than buying one.
Bob
 
I've done shafts like this with a woodruff cutter, same idea as the 1/8" endmill but cheaper and less "breaky".
 
Why the 1/8 end mill? Each side of the spline could be cut with any diameter desired. The cutter clears the spline below it. Then you need a cutter who's diameter will clear the next spline when the part is indexed 30 degrees, as you only need to clear the minor diameter 1/2 way away from the side of the spline, get the other half from the other side. But practically, once you cut each side of each spline, and then rotate the part 30 degrees and make a tangent cut between the splines I expect the amount of metal left can be removed by barbering much faster than machining.

You don't say how long of spline you need. The part could be shaped by stroking with a quill tool if you have a rotary table, as long as the spline part isn't over about 1" long. For a long part you could put a degree wheel on a lathe spindle and broach it with the carriage.
 
Last edited:
Where does the part rest on a spline, is the contact supposed to be solely on the keys, or on surface I will mill away?
Straight-sided splines like these have three classes of fit - major diameter, minor diameter and (rare) side fit. Major diameter is the most common. Those will usually be in an even inch dimensions, such as 1", 1.25", 1.5" and so on. Usually but not always you can tell if it's minor diameter fit because the roots will be ground. Almost always the od is ground.

Watch the corners, that's where you run into interference so make sure that one part or the other is relieved so they fit on the parts you want to fit, not hanging up on the corners.

I doubt there's a cutter for doing this job is there? Is there any simple way for shop with out gear cutting equipment to make these?
Ash gear has cutters for most of the normal types. Your print has everything except what you need to know, good work :) OD counts, minor diameter counts, spline width counts. That's all that matters. It's worth buying one if it's a standard size. Almost always it will be. They aren't very expensive.

You can also make your own if it's only a few parts, using a piece of high speed as a flycutter.

For the id spline, you're stuck stroking it in the mill or with a shaper or slotter or you can buy a push broach and have a tool grinder arc the teeth and make yourself an indexing bushing. That won't be as pretty but works okay for a few parts.
 
It looks like I can buy this shaft and machine it down, then I can counterbore and pin it onto my existing shaft rather effectively.

Then the only question becomes what to do on the bore side. I have a lot of gears that will run on this shaft to make. I can't find any premade push broaches for this size readily available but it looks like an indexing bushing and a 6mm broach will work. I am thinking so long as I can locate on the minor diameter I won't need to arc the teeth. Am I wrong?

Anyone know where to get a broach for this?


spline shaft.JPG
 
I am thinking so long as I can locate on the minor diameter I won't need to arc the teeth. Am I wrong?
It's hard to know from here how much runout you can tolerate or how the original parts were set up ... you'll have to determine that yourself but in theory, it can work.

Anyone know where to get a broach for this?
You want to arc on the major if possible ... it looks pretty hokey the other way. I have taken a regular push broach and just ground an arc on the outer face. Didn't even have top rake, just flat and parallel to the back side. Most of the teeth don't show any arc, it's just the last few. Looked ugly but worked pretty well.

Another thing to try is, there are broaching services. In California Pioneer Broach is nice and helpful and cheap and they have a ton of standard broaches. Once you start running a push broach through a part twelve times (six splines, thru once then add the shim then push again, six times per part) a few dollars for a broaching service will seem very reasonable :)
 
For the shaft, call Ash gear for a space cutter- if you want to make a flycutter, the formulas for the angles are in Machinery handbook under straight sided splines. For the internal, keyseater with an index attachment, slotter or handbroach with a keyed bushing. No the major diameter does not need to have a radius but......... call some broaching houses - you will be much happier and the job probably won't cost you as much as buying a keyway broach.
 
I need to make a splined shaft with matching splined parts in a limited machine shop;

The internal cutter seems rather easy to make. I will just create a broach holding tool roughly as follows, with a square key in the red zone and a slot for the broach at 60deg.
View attachment 426625
The male shaft is the one that I am scratching my head thinking of how best to do. I have an indexing head and via endmills I could carve out the teeth roughly as seen in the image below. But that leaves me with a flat portion. Where does the part rest on a spline, is the contact supposed to be solely on the keys, or on surface I will mill away? I doubt there's a cutter for doing this job is there? Is there any simple way for shop with out gear cutting equipment to make these?

The plans I have, tell you to mill a slot and silver solder in keystock. I am starting to think this maybe the best way to make these parts.
View attachment 426626
If you look in the Machinery's Handbook there are SAE straight sided splines listed. There are 3 fits, A, B, C. These are all major diameter fits so the minor diameter just needs to be smaller than the minor diameter of the fit. When we make custom replacement shafts for high torque applications we mill the sides with the largest end mill that won’t touch the other side, then take out the center for clearance in the sleeve. We design for the C fit as it has the smallest minor diameter on the internal spline.
If you just need a shaft, Hub City sells some sizes.
 








 
Back
Top