We were chatting this up over on a different thread on spline count: http://www.pirate4x4.com/forum/showthread.php?s=&threadid=91347

...and it drifted to spline SHAPE. This one has always made me curious...

Not sure what you call straight spline- coarse spline? Involute spline can be up to 35% stronger than coarse spline.
I was talking about spline profile -- involute (hobbed) vs. straight (milled/cut). I recall the 1/3 strength difference (between A and D below) ... what I'm wondering about is the strength of one fit into the other...

a.) Involute spline axle fit into an involute spline differential.
b.) Involute spline axle fit into an straight-cut spline differential.
c.) Straight-cut spline axle fit into an involute spline differential.
d.) Straight-cut spline axle fit into an straight-cut spline differential.

I can't find my SAE handbook to look it up! :emb4:

There's a whole lotta folks running fly-cut axle splines into involute-broached differential side gears (C, above)... how much weaker is it really?

Randii

The involute spline is produced by mill cut or rolled spline, rolled involute spline is the ultimante,the grain of the material is compressed, this process must be prefromed before heat treat.Mill cut involute splines can be done before and after heat treat, up to 64 rockwell scale C. steve differential eng .inc.

Originally posted by steve gerstner
The involute spline is produced by mill cut or rolled spline, rolled involute spline is the ultimante,the grain of the material is compressed, this process must be prefromed before heat treat.Mill cut involute splines came be done before and after heat treat, up to 64 rockwell scale C. steve differential eng .inc.

So to be clear, the strongest of all splines would be rolled involute, when used with a matching female involute.

I guess what I'm wondering about is the specific case of having axles resplined locally, with a fly-cut process. My understanding was that this left 'straight' walls, with no involute curve...

How much weaker is:
* this type of straight spline paired with an involute female spline?
* post-heat treat machining, relative to a rolled spline?

Randii

you can get an involute profile from a single point milled spline, it all depends on how you grind the cutter, whether or not the people doing the resplining actually do this, I dont know, the most common way to form splines is on a hob, shaper or roll them if you have the quantity or equipment, the ultimate spline would be to roll them after heat treat if you have the dies to do it. As far as what shape is strongest with what, I think that for what we do it doesnt really matter, It would be hard to find actual testing data or research for what you are asking, what you are asking is pretty much only used in automotive aftermarket axle manufacturing and I doubt that anyone has a good enough reason to spend the money on testing. Basically what ever method an axle manufacurer is using, they are going to tell you it's the best way.

Originally posted by steve gerstner
t.Mill cut involute splines can be done before and after heat treat, up to 64 rockwell scale C. steve differential eng .inc.

sure but nobody builds a stock tool that would allow you to cut heat treated involute splines. if you built a custom tool who made it and how much was it ? i would be intreasting in getting one.

Originally posted by randii


I guess what I'm wondering about is the specific case of having axles resplined locally, with a fly-cut process. My understanding was that this left 'straight' walls, with no involute curve...

Randii

i don't think you have a choice if you are resplining a axle. nobody i know of has the tooling to cut involute splines in a heat treated part. it is possible to build the tooling but as far as i know all the shops just fly cut the splines. i think the key is to find somebody who does it well.

alot of this is a moot point since the splines are rarley the part of the axle to fail. even when mismatching spline designs and pressure angles.

Originally posted by GOAT1
Basically what ever method an axle manufacurer is using, they are going to tell you it's the best way.
I hate that. I bet you're right, but I still hate that. :(
I see enough of that when everyone with a left-handed flugerbuger says that right-handed flugerbugers suck, and vice-versa. Folks get soooooo attached to whatever it is that they run, and having vendors do the same is human nature, I suppose, but ultimately muddies the water.

Originally posted by camo
alot of this is a moot point since the splines are rarley the part of the axle to fail. even when mismatching spline designs and pressure angles.
But that goes back to the other thread http://www.pirate4x4.com/forum/showthread.php?s=&threadid=92932 and the comment that few folks understand all aspects of the equation. If few folks use a truly optimized axle (from the nitty gritty of alloy composition and heat-treat, to the matching of spline profiles and angles, to torsional-twist-absorbing neck-down)... there's no real advance in technology.

Call me a geek, but there's something pleasing about designing the right part for the task at hand, as opposed to stuffing the biggest freaking part in the space available. I enjoy the sight of a Ford small-block in a Miata, but I groove on watching a stock 60's-vintage Morris Mini clean that Miata's clock through the cones, too.

Randii

Originally posted by randii


Call me a geek, but there's something pleasing about designing the right part for the task at hand, as opposed to stuffing the biggest freaking part in the space available.

AMEN....I have been kicking the idea around about forming my own business when I get out of school to actually engineer this stuff. I think a team of a couple ME's and MET's could come up with some seriouly cool stuff for wheelers.

I hate that. I bet you're right, but I still hate that. I see enough of that when everyone with a left-handed flugerbuger says that right-handed flugerbugers suck, and vice-versa. Folks get soooooo attached to whatever it is that they run, and having vendors do the same is human nature, I suppose, but ultimately muddies the water.


I HEARD that brother! You're a man after my own heart - but you already knew that! I don;t have any help with this topic, but just so you know you're not the only "geek" who cares about such stuff.

Remeber when I started all the fuss about the "neckdown"...theory asys one thing, but there was a lot of "real-world" experience possibly exhibiting something different...and I never felt we really reached much of a conclusion.

Was it lack of data, lack of scientific control of variables, lack of understanding all the variables???

I still wonder whether the 'sport" will ever get "big enough" that this sort of testing and engineering will ever be done with an eye specific to offroad / rockcrawling use...the way F1, SCORE, and even passenger cars (I'm thinking crash testing specifically) where they almost completely understand all the factors and where the weak points are?

I dunno. Sorry for hijacking and ranting!

Originally posted by camo


sure but nobody builds a stock tool that would allow you to cut heat treated involute splines. if you built a custom tool who made it and how much was it ? i would be intreasting in getting one.
Yes your right, i had to make my own tooling.After cutting thousands of axles for 16 years one can develop a wealth of information on cutting inserts.It is no problem to spline a timken bearing race.But for the axles with rolled splines, these slip in to a side gear that is broached, this cuts the grain of the material so what can you do? I have seen them fail both ways. steve differential eng. inc.

Originally posted by randii



But that goes back to the other thread http://www.pirate4x4.com/forum/showthread.php?s=&threadid=92932 and the comment that few folks understand all aspects of the equation. If few folks use a truly optimized axle (from the nitty gritty of alloy composition and heat-treat, to the matching of spline profiles and angles, to torsional-twist-absorbing neck-down)... there's no real advance in technology.

Call me a geek,

Randii

ok your a geek :flipoff2:

as far as my comment about it being a moot point. it is a worthy discussion but the fact is in the real world nobody is actualling resplining axles using a involute spline and only a few even build custom axles with a involute spline. there are lots of folks who understand what we are talking about. and more i am sure are learning from this thread.


let the techno babble continue. :D

Originally posted by steve gerstner

Yes your right, i had to make my own tooling.After cutting thousands of axles for 16 years one can develop a wealth of information on cutting inserts.It is no problem to spline a timken bearing race.But for the axles with rolled splines, these slip in to a side gear that is broached, this cuts the grain of the material so what can you do? I have seen them fail both ways. steve differential eng. inc.

would you be intreasted in building me a tool ? do you think a bridgeport using the stock r8 style collets would be able to hold every thing rigid enuff to get to get the job done right ?

Here you axle guru's go. We have used this spline and it is 80% stronger than a regular splines. http://www.generalpolygon.com/why.htm

A rolled spline has 2 times greater fatigue life (rule of thumb) than a cut spline.

Cut splines can be straight or involute, the difference is in the tooling. Yes you can have it made. Yes it's expensive.

The rolled splines I've dealt with are done pre heat treat. The machine setup is very time consuming and the dies would wear quickly if done post heat treat. The big issue is how the heat treat effects the spline profile and if it can be controlled. The products I've dealt with do not "typically" have a problem.

When an OEM designs a splined joint it's done as a matched set. Involute/involute or straight straight. I couldn't find any data on involte/straight wear or life reduction. The spline pitch will be the same. The difference will be in the profile of the spline itself. Then the spline "fit" will come into play. Loose fit, Close fit, line fit, interference fit. Depends on the useage of the parts.

In a differential they would be between a loose fit and a close fit, depending on the tolerance from the drive hub to the diff side gear and the expected deflection in the housing and tolerance in the bearing setup.

What it will typically come down to is wear. The involute profile will wear slower than a straight cut profile. The stress concentrator where the spline exits the side gear will also decrease the life or stregth of the part.

Hope some of this helps!

Originally posted by BillaVista



Was it lack of data, lack of scientific control of variables, lack of understanding all the variables???

I still wonder whether the 'sport" will ever get "big enough" that this sort of testing and engineering will ever be done with an eye specific to offroad / rockcrawling use...the way F1, SCORE, and even passenger cars (I'm thinking crash testing specifically) where they almost completely understand all the factors and where the weak points are?



I think it's probably the lack of understaning entirly what is going on. The thread where a poll was done to see where the shafts broke a magority were near or at the splines. Rhat means whoever made the shaft did not do their homeworkm wether it be incorrect splines, heat treating, or the wrong axle profile. From what I have learned in school, the profile of the shaft after the spline is VERY important. Proper necking will elminate your stress concentrations that lead to breakage. Another interesting asspect to look at is fatigue life. As it is now we don't have to really worry about fatigue because the shafts aren't lasting long enough, OEM shafts one the other hand have this factored in since a shaft has to last the lifetime of the vehilce.

As I was saying before I would be very interested in getting into the design, testing, anlaysis, and actual R&D type business for the wheeling community but not sure if the demand or money is there. Such a business would also help out in using better and maybe more extensive use of aluminum alloys, steel alloys, and perhaps even composite materials. Look at what they use in CART and F1 racing.

I have a Dream.....:D :D

Originally posted by Weasel



As I was saying before I would be very interested in getting into the design, testing, anlaysis, and actual R&D type business for the wheeling community ..............
I have a Dream.....:D :D

hey fawker thats my job :flipoff2: dream on :flipoff2:

too bad...I thought it first......:flipoff2: :flipoff2:

No time to respond now, but DAMN I'm tickled to see the responses... getting folks to talk about this has been like pulling teeth.

In Kentucky.

At an old folks home.

Get yourself one if these rigs: http://www.colonialtool.com/spline.htm

I've been doing some reading and Mark Williams makes some convincing arguments for the 45* pressure angle on the 24 pitch splines. One of the features I like is that is allows you to have the same bearing surface on the face of the spline, but reduces the intrusion of the base of the spline into the minor diameter by a good bit (about 18% by my thumbnail numbers). I'm not sure how I feel about the extra outward load the 45* pressure angle places on the broached end of the splined connection.

I'd also like to see numbers on shock load reduction due to the elastic responses of tapered shafts over different lengths. I may play with that at lunch today in a spreadsheet. I bet the numbers would be interesting.

on top of that, I wonder what kind of efect you could see on a tapered shaft with spines that fully engage the broached end of the connection. this would be where the splines end and the shaft starts necking doen before it exits the outer face of the carrier. I bet you could eliminate a lot of stress risers in the shaft that way. I wonder if you'd create more risers in the borached end becuase of it. hmmm...


LT1YJ, any thoughts on a FEM? shouldn't be that difficult.

Apologies to Randii for hijacking this thread into general shaft design....

I think one of the chief problems we have, is a lack of complete understanding of what it is we actually want (need) in a shaft.

Do we want to maximize ability to withstand one-time loads, do we want to maximize fatigue life, or most likely, some compromise, and if so in what proportion?

I think, even though most breaks appear to be a one-time overload, fatigue life has to be important, especially since we are likely subjecting our axles to the worst case scenario of loads that cycle from full on to full reverse. By this, I mean imagine the stress, and corresponding strain, experienced between a heavy wheel and tire spinning fast forwards, that suddenly gains a large amount of traction (say in a steep climb). That same axle them may experience stress and strain in the other direction...say you're trying to back out of stuck, tire is bound up in the rocks and you have to romp on it in reverse.

In this scenario (high on-off-opposite strain) the part will eventually grow weaker due to fatigue, and may eventually fail at a load that it could easily have withstood when newer.

I've read a bit about the difference between the appearance of a fatigue failure (visible beach marks, smoother appearance) compared to a sudden one-time overload failure (uniform, grainy texture). One thing I don’t understand is this, how will it appear if the one-time overload failure occurs because of a shaft already weakened by fatigue, as in the case above?

Then of course we have the situation where most people can't or don't care to analyze the broken parts or the circumstances...and it's hard to gather data.

Then of course, we run smack into the AWGAF factor (Awww...who gives a fawk), where most of us get fed up and just smack in the biggest stuff we can and go wheeling!

One thing does seem intuitive - whatever design decisions / compromises the OEMs use, is pretty clearly not optimal for us, and I suspect the same is likely true of drag / racing parts design. Heck, I remember reading one guy saying that oem's intentionally neck down front inner shafts near the yoke intending to weaken them there so that it would shear in the case of a diff seizing, so the wheels wouldn’t lock and cause an accident????

I'd guess we need a shaft with good fatigue life, but with a fairly heavy compromise towards resistance of one-time overloads.....question is, what does that shaft look like?
Crap..I dunno, but I wish I did!

Originally posted by BillaVista
I've read a bit about the difference between the appearance of a fatigue failure (visible beach marks, smoother appearance) compared to a sudden one-time overload failure (uniform, grainy texture). One thing I don’t understand is this, how will it appear if the one-time overload failure occurs because of a shaft already weakened by fatigue, as in the case above?


A shaft "weakened" by fatigue will have a crack. The crack could be macroscopic or microscopic depending on the number of cycles endured. Either way the part will achieve full section failure due to fast application of strain and can be described using fracture mechanics. Take the largest flaw in the highest stress region and then look at the fracture toughness of the material (K1C). Sometimes the heavily heat treated parts will have the lowest fracture toughness. Anyway, the fracture toughness, the size of the flaw, and the crack tip radius all influence how much load the part will be able to handle before it fails.

One interesting thing about torsional fatigue failures is they can take on several failure modes. I've seen quite a few torsional fatigue cracks grow along the axis of the shaft and then fail in a spiral along the shear plane. I've also seen a few torsional fatigue failures that grew from the outside in and never grew along the shear plane at all. It looks almost like the shaft was cut.

For the most part our axle shafts don't see high cycle fatigue. They typically see low cycle fatigue with load applications close to the material yield strength. There is a big difference in the way a part is designed for high or low cycle fatigue but one thing in common is to reduce or eliminate stress concentrators. One way to significantly improve the life and shock load capacity of the shaft is to polish it to a mirror finish. Any nick or flaw in the shaft will decrease the life or could be an initiation site for fast fracture. Another way to improve the life is to use eliptical radii at the yoke end instead of a constant fillet radius. Again ground to a polished finish.

"In my opinion" the material fracture toughness should play a much bigger role in material selection for axle shafts. I have not taken any time to evaluate the materials and don't know if the K1C values are redily available for 4340 or 300M. I think some time with a metalurgist would be appropriate if someone really wanted to minimize axle shaft failure.

Originally posted by Sundowner

LT1YJ, any thoughts on a FEM? shouldn't be that difficult


FEM or FEA? A finite element model would be very easy. It's essentially a 2d mesh extruded the length of the side gear and the length of the splined shaft. There would need to be a reasonable length of axle shaft included to get the wrap and to utilize St. Venant's principle. It would only need #splines/720 degrees of model and run as a symmetry model (1/2 of a single spline profile).

I could build the mesh in a few hours and probably have the model running in a couple of days. Iterations would be very fast because all that would change is the face of the spline.

You also mentioned shock load per unit length of axle shaft, you were looking at a tapered shaft but what about just the shaft length leaving the diameter constant? I've noticed most failures are on the short side shaft where there is much less torsional elasticity. I'm sure the shorter shaft decreases the shock load capacity.

Apologies to Randii for hijacking this thread into general shaft design....
Apology NOT accepted. :flipoff2: This is good tech (even if Camo calls it techno babble -- at my age, it is the only thing 'techno' about me :p ) and I'm wondering about the same things.
Camo has a demigod building his axles -- I know they'll be built right... what I'd like to reconcile is textbook training from long ago with common practices now, and extract some reasons WHY things are done the way they are. The expense of the process has significance, but it simply CAN'T be the only thing to go by. It would be cool to get some strength ratings and identify whether a 35-spline fly-cut, sans-post-heat, non-necked shaft is all that much stronger than a through-hardened rolled-involute 31-spline Dana 44 shaft with textbook taper. Girth is always impressive but if the splines candycane before the shaft body yields, does it matter?

Camo hammered the real reason I'm asking -- very few real-world shops (not the ones local to me) mill with a curved cutter...

Steve Gerstner (a demigod in his own right) had an interesting point: even the sweetest rolled splines generally slip into a broached side gear, and that process shears cross-grain to the metal... I think he was questioning whether their was much advantage to rolled splines. I'll throw one more question on this slippery slope -- once you get the strongest spline, if it worth using a wire-EDM process to tailor-match the female spline to the mail spline (straight, involute, or polygonal)?

Dunno. Would love to see some stats. I don't have the answers -- just trying to facilitate the questions.

Randii

lt1yj said that the chief difference between involute and straight splines is in fatigue life -- and Steve said they both fail, in the end... Something else to think about is slop in the system -- involute can allow a tighter fit. Does it matter for rock-crawling? Not unless we can make splined stretch to lifespans of years in competition-style abuse, instead of months. If I were an axle manufacturer, there;'s would certainly be NO WAY I'd lifetime warranty this sort of application... too many variables.

Sundowner, I've done the math on expanding the base circle/included circumference by diminishing the included angle, but hadn't considered the load displacement. Applied uniformly around the splines, isn't that self-cancelling? Doyou have links to Mark Williams, or is this out of printed material?

These should be pretty simple FEA models, but I'm sure someone has already done the work (where's a grad student when ya need one?). I'm even willing to cart my ass off to a brick-n-mortar library if someone has references. I lost my damn SAE pocket guide in my house somewhere -- bugs me, since I know that some of this is in there... from polishing shafts to ramping diamaters to material properties, at least in overview format.

Fun discussion!

Randii

Originally posted by lt1yj



For the most part our axle shafts don't see high cycle fatigue. They typically see low cycle fatigue with load applications close to the material yield strength. There is a big difference in the way a part is designed for high or low cycle fatigue but one thing in common is to reduce or eliminate stress concentrators.

Yep...what he said.:D :D

I love how you guys can take a very intelligent, college educated person such as myself and make them feel like a total idiot. Thanks guys :flipoff2:

that said i'm following the basic structure of the discussion but my big question is WTF is an involute spline. Oh and i read the really confusing explanation of hobbing splines yesterday, but how are splines "fly-cut"?

Dallas
sorry i'm hi-jacking the thread as well

yeah, a FEM.
I'm curious as to how the shaft would react at the toe of the ramp up from the reduced shaft to the spline's minor axis over a fatigue life. the section properties pick up fast at that point and the elastic response is gonna drop off just as fast. Add to this, you've got a shaft with a given capacity for torque and fatigue life for a given length. a shorter shaft of the same diameter should have a shorter life. My guess would be that we'd have to make it thicker to fight the shock load instead of thinner in order to get a strength on a similar oroder to the longer shaft.

Interesting what you said about fracture mode. Every snap Iv'e seen in the lab on decent steel has been the 45* spiral along the long. axis of the shaft. I've only seen the 90* cut in relatively soft materials. I wonder what effect gun drilling would have on the torsional capacity of the shaft, and the cracks ability to track through the section.

As far as toughness on the shafts is concerened, there's gotta be a point on the graph where the toughness is gonna cross the elastic limit of the material and your gonna lose strength to brittle failures.

Randii, look on MW's site under "in the news" there's some tech articles in there repritned from varioous rags.

I'm out until thursday, that sucks, this thread is starting to get fun :D

Definetly College level!

Randii, as far as EDMing the female part, I think the grain structure would be better than that of a broached part. BUT I still don't think it would be as nice as the rolled male part. What about rolling the internal profile? Or you could use the same technique they use on some firearms and use a carbide die and hammer the material to conform to the profile. This would work better with smaller profiled splines.

Being a machinist, and ultimately the guy that would have to make these, I would just broach it or EDM it depending on the volume of the parts. EDM is a long process, then again I get paid by the hour :D

Great reading...I love to learn. (So Thanks) I have a few questions myself.....but you will have to deal with the under educated farmer mentality when reading.

#1 All personal values and needs aside..given the multitude of ways a wheeling rig can strain an axle, could one material or process of manufacture ever be "perfect"? I once had a custom short side shaft with no neck down and a stock longside combo, when at the dunes I was stuck in a bowl with no way to go but backwards..lots of weight on front axle nose down in a hole. I just "caressed" the gas and SNAP!! When removing the shafts they had both broken..the custom shortside with no neck down snapped in the middle of the shaft (Splintered basically) The stock shaft broke at the neck down before splines. The painted lines on shafts showed the long axle had twisted 3/4 of a turn before breaking...and the shorter shaft had made about a 1/4 of a turn. Now I am no engineer or even capable of speaking in the terms many of you all do.......... but, given the above example wouldn't you need two differant shafts to have the perfect shaft for a off set diff? Reason I asked is not being a quick learner I installed identicle back up shafts and a day latter found myself in a very similar situation...when it broke, it was at identicle failure points as the first set.



NoRM

Norm,

As of now no one knows the ideal alloy or construction. That's what would be fun do find out. And yes I belive with some good research into this you could design a axle shaft to last much, much longer then we are currently seeing.


In the limited info I have learned from classes the short shaft would have been more of a brittle failure while the long shaft had some kind of ductile failure. I'm not expert in failure anlaysis, thats the Met's job.

As far as gun drilling, this is used in some applications and with good sucess I belive. It was discussed at our last baja meeting. As far as I understand it the core doesn't add much strength to the shaft so removing it can reduce the material in which interal cracks could form. I'll see if I can find more info on this.

For the most part our axle shafts don't see high cycle fatigue

Yea, I guess not, at least not relatively speaking, when you consider a bolt that holds a con-rod cap on can see millions of full on-off-on cycles in a matter of hours.

could one material or process of manufacture ever be "perfect"

Nope, that's the rub. All design is a matter of compromise. It's a matter of where you want to compromise!

I installed identicle back up shafts and a day latter found myself in a very similar situation

Do you mean identical each side, or the same as the first set? That kinda makes a huge difference in what your observations say. Great info - I wish more would have that level of detail in break reports - it would help us enormously. Love the painted line trick - cool.

Originally posted by Magoo
What about rolling the internal profile? Or you could use the same technique they use on some firearms and use a carbide die and hammer the material to conform to the profile.

I'd think rolling the internal profile would be very spendy, although very cool. I'm sure it's possible--I believe most nuts are internally thread-rolled, and if you can roll threads, you should be able to roll splines.

EDM would be preferable for one-offs, just 'cause of the lack of upfront tool-building cost, I'd think.

Is there a way to build a "forming" broach (similar to a "forming" tap) that doesn't cut material away? That'd be about as close to rolling internal splines as I think you'd likely get economically.

Realizing full well that it's not a common thing, did anybody else (nobody's commented on it) take a look at Donovan's polygon info? That'd be really cool if it'd take on and run in the 4WD industry--getting into the "why use splines at all" discussion. :)

Randii,

My Machinery's handbook has almost 30 pages on involute splines!

No - I'm not going to type it out for you :flipoff2:

Originally posted by Scott@Rockstomper


Realizing full well that it's not a common thing, did anybody else (nobody's commented on it) take a look at Donovan's polygon info? That'd be really cool if it'd take on and run in the 4WD industry--getting into the "why use splines at all" discussion. :)

Scott thanks for noticing the polygons. I believe that is the best way to build an axle but I have not had time to build one with the polygons yet. I was told by the polygon companies that this will be about 80% strong than a regular type spline. We have made them for Eagle Claw and they work quit well for them.

Randii my brother worked at Mark Williams for serveral years and they seen a lot of Moser shafts break right on the spline before it goes into the spool or side gear. Maybe that is because of the straight spline going into a involute spool/side gear.

Stinkbug, and involute spline looks like a gear tooth in that the sides of the spline is curved like the side of the gear tooth.

Originally posted by BillaVista
Do you mean identical each side, or the same as the first set? That kinda makes a huge difference in what your observations say. Great info - I wish more would have that level of detail in break reports - it would help us enormously. Love the painted line trick - cool.

Sorry yeah that wasn't very well spoken...the 2nd set was broken the exact same way...shattered on short side and a clean shear at neck down on long side. And I could verbally recount lots of dana 44 axle breakage data, I tried my damndest to make that thing live in the front, and I can attest to 27 shafts in one season. Probably 40 total over a period of 2-3 years. * like I said I dunn learn fast* But I will tell ya, I have had more shaft failures than I did joint failures in my rig........I notice about the oppisit in many other rigs.

NoRM

Oh and i read the really confusing explanation of hobbing splines yesterday, but how are splines "fly-cut"?
Geeze. I thought I did a good job with the hobbing explanation. :( Based on my lack of success there, I'll let someone else explain involute and cycloidal tooth forms.

Randii, look on MW's site under "in the news" there's some tech articles in there repritned from varioous rags.
Exxxxxxxxxxxxcellent. Nice find... http://www.markwilliams.com/news/index.html

What about rolling the internal profile?
Gulp... :eek: I thought rolling and hobbing was expensive (compared to broaching), and that EDM was a step further out. I shudder to think what internal rolling would cost, or the machine that would do it! Let's get Camo to do it and find out on his dime. :p

Randii

I would tend to think the internal splined female end of the connection would be intrinsically stronger than the male end due to the fact that the female end really has no minor diameter.

i can't say i have even heard of internaly rolled threads. broaching is inexpensive once you own the tooling. example: a 40 spline broach is $2500 to buy and about 10 bucks to have a shop ram the broach through the hole if you are only doing one part. it is even less if you have several parts.

Question - how are female threads formed in SAE nuts?

I know they're not "cut", because apparently they used to be, but this is no longer permitted?

Dunno if it's relevant, but it might be.

In case it isn't, I'll try and add some tech:

From the Machinery's Handbook:

Splines having straight-sided teeth have been used in many applications , however, the use of splines with teeth of involute profile has steadily increased since 1) involute spline couplings have greater torque-transmitting capacity than any other type; 2) they can be produced by the same techniques and equipment as is used to cut gears; and 3) they have a self-centering action under load even when there is backlash between mating members......The general practice is to form the external splines either by hobbing, rolling, or on a gear shaper, and internal splines either by broaching or on a gear shaper. The internal spline is held to basic dimensions and the external spline is varied to control the fit.

Keep in mind mine is the 24th edition (1992) so may be a bit dated.

So to your initial question Randii I would say that straight splines in an involute female would result in a reduction in torque-transmiting ability, and a loss of self-centering inder load, as well as (obviously) a poorer fit. How much, I dunno.

Question - how are female threads formed in SAE nuts?

I know they're not "cut", because apparently they used to be, but this is no longer permitted?



The thread form isnt cut then it must be formed, and uses a different tap designed to do this. For cutting internal threads, either with a tap or a lathe, the drilled hole will become the minor diameter of the threads. To form internal threads, the hole is bigger than the minor diameter. The tap displaces material to form the "valleys" or major diameter. The displaced material fills in the "peaks", forming the minor diameter of the nut.


this is a great thread!! hehe



Ben

BTT for the discussion in: http://www.pirate4x4.com/forum/showthread.php?s=&postid=1018045