View Full Version : How to respline automotive axles......

02-28-2005, 12:20 AM
Is it possible to respline automotive axles with a vertical mill and an indexing head(s) or is it better to use a horizontal mill with an apprpopriate cutter and indexing head. I have two 35 spline Ford axles I'd like to try and respline but I do not know the process. Any ideas?? I realize that they will need to be heat treated again but I'd like to see how difficult it is. Thanks for any help, emj.

02-28-2005, 01:03 AM
Why would they have to be heat treated again, as long as you don't heat them up, I would think they would be ok. You could grind a toolbit for a fly cutter to the right profile to cut the splines and then use your indexer. The local shop here that shortens and resplines axles uses a broach.

Spin Doctor
02-28-2005, 07:28 AM
A lot will depend on the profile of the spline itself. If it is an involute spline then the original production process most likely utilized a hobbing machine or a rolling operation similiar to the process used to roll threads on screws and threaded rod but held to much tighter tolerances. To cut this type of spline in a vertical or horizontal mill with an index head the cutter tooth profile should be an exact match for the diametral pitch of the spline and the involute profile for that numver of teeth. For the cost of the cutter it might be cheaper to just try and contact a local shop that cuts gears if one is available. For a parallel key spline I have in the past cheated and used woodruff cutters to cut the teeth in a series of three operations where you cut the gullet, top and bottom side of the tooth. But if cut in a mill then the right cutter should really be used again. Re-introducing the cost factor. And if they are parallel key splines then are they top fitting or bottom fitting and what class of spline are they. Press fit, sliding fit or running fit.

[This message has been edited by Spin Doctor (edited 02-28-2005).]

John Stevenson
02-28-2005, 08:02 AM
As Spin says but with one point.
If they are involute splines they will have been hobbed.
I may be wrong but I have never seen single flute cutters for involute splines.
Gear cutters yes as these were out before hobbing but involute splines came in quite late and hobbing is the norm so I can't see who would make single cutters when the manufacturing base ie hobbing was already there.

John S.

02-28-2005, 09:10 AM
I recently purchased a used vertical mill, a used horizontal mill and a used lathe for an upcoming automotive project as well as a vertical/horizontal indexing head and rotary table. I would like to try to shorten and respline the the axles but I do not know the correct way to do the job. Machine shops here will not respline axles due to liability issues. They used to a few years ago but have since stopped. I went to most of the shops listed in the phone book in person with no good luck. I thought I could get a keyway-like cutter that match the splines and use the indexer to rotate the axle then raise the table on the horizontal mill and move the table left or right to cut the splines to length. If you could explain the total process or direct me to a source, it would be greatly appreciated. Thanks for your time, emj.

02-28-2005, 09:53 AM
I used to manufacture output shafts.

The spline is rolled and hardened to about 2" behind the spline.

You can cut them on a horizontal, but they wont be as strong (but should still work). The nature of rolling makes a VERY strong spline. When cutting, you introduce tons of stress into the spline. If you have the ability, you may want to get them shot peened, but I'm not sure how well it will work.

Hardening will be more difficult though. They are induction hardened, reproducing this with a torch or kiln or whatever will be difficult.

I can't remember if the ford 35 is involute or not...even if I could, I probably couldn't release it.


Mike P
02-28-2005, 10:50 AM
Shortening and resplining axles may not be such a sound idea. Many axles have an increased diameter where the splines are cut. This fattening serves to reduce the fatigue on the splines, which are really just giant cracks, waiting to keep going.

Companies like Moser and Strange will make shortened axles for not a terribly large amount, and they're done absolutely right.

Mike P

02-28-2005, 12:03 PM
EMJ , I have had 9" axels re splined by a local machinist beforeI set up my shop, He would use a specially ground cutter similar to a keyset cutter and a dividing head in a bridgeport type mill. No rehardening was neccisary. As for the diamiter of the splined area, this was turned on the lathe prior to cutting the splines, and an the area just outboard was reduced to the root size of the spine and tapered back into the axel od to minimize stress risers.He would always request you 3rd member to match the splines exactly to your carrier. Good luck.

02-28-2005, 06:12 PM
emj, try this and no indexer required. I will leave it up to you to find a cutter with the proper profile. Horizontal would be my preference but either, with the right cutter will do. You will have to anneal the shaft because they are case hardened. That is unless you can get a carbide cutter. Cut the splined end off an existing shaft that matches what you want to do. Cut your new blank shaft 1" longer than the finished shaft and weld in place the splined stub end to end. Try to get it as close as possible in alignment but it is not critical. Clamp this on your mill table and simply rotate for each grove and follow the pattern of the old stub. Start your cutter in the grove of the old stub adjust for fit between the ridges as you cut. Take your time and you will have a perfect matching spline. When you are finished you cut that 1" extra of along with the weld and the old stub. I use to do this to 5 ton truck rear ends when we adapted them for use as tugs at the airport. A note, when you are welding the stub to your blank. make sure the weld is machinable. Rods like 7018 play hell with the cutter and alignment. We use to send our shortened shafts out for heat treating after but we anealed them ourselves with a torch and in tub of silica sand.

02-28-2005, 07:00 PM
I guess what I probably should do is just continue the splines up the axles toward the flanges then cut off the excess. I only need to remove a few inches off of each axle but I really need to find the cutter that will do the job. These 35 spline axles were made by Moser so they do not taper anywhere and have stock-type Ford splines since they slip in a Detroit Locker differential. Anyone know where to find the cutter needed for the job or is it a trial/error proposition?? Thanks for everyones time, emj.

02-28-2005, 08:15 PM
There was a post awhile back were a fellow had used a triangular carbide insert for the cutter.Looked good to me.

Don't worry about it too much,those splines are not that accurate from the factory.They DON NOT make full face contact with the splined bore,at best they are only making %35-40 contact.

As for indexing,Ibew has the solution for that.His fix is using a extra spider gear welded to an angle iron thats bolted to the mill table.In use the axle is dropped in and out of the spider one tooth at a time,when your happy with the fit,cut the axle to length and your done.

03-01-2005, 12:00 AM
It appears that an old spider gear/angle iron with an indexer and horizontal mill may be the easist way to extend the splines up the axle then cut off the excess splines. The splines are not parallel but taper to form a sort of triangular pattern. The big question is, where does one find this spline cutter for a horizontal mill?? Can it be purchased or is it a homemade cutter? Thanks again,emj.

03-03-2005, 01:37 PM
I'm new to the board, and this thread caught my eye because I need to do the same job. I plan to try a flycutter with a handground HSS or cobalt bit. Can anyone tell me if I can get away with cutting the splines without annealing the axle?


03-03-2005, 08:26 PM
I think I'm the guy weirdscience was thinking of. He gave me the clue about using a carbide insert in an MCLN tool holder to do the turning work. Thanks again!

Here's the photos I put out a few months ago when I did my first shaft http://members.tcq.net/jnutter/machineshop/

I spent last weekend doing this job. It's tedious when you start to do multiple shafts...

I use a cutter I bought from a guy on the Pirate4x4.com board LINK (http://www.pirate4x4.com/forum/showthread.php?t=219732). The cutter uses 3 TPG 321 inserts and it cuts 30 degree splines. It is very possible that your Ford 9" 35 spline shaft may have these splines, but some aftermarket manufacturers also made 35 spline shafts for 9"s with a 45 degree spline. You should be able to do some searching and find out. I know I've seen that info posted on the pirate4x4.com board.

I do this job on my horizontal mill, but there's no reason that you couldn't do it on a vertical mill. I think you would want a power feed though. The cut with the TPG 321 inserts is a forming cut, and you only want to feed .002" to .003" per tooth. Plan on running the tool at about 500 rpm, and this works out to a speed that would be painfully slow to hand crank through 35 splines. I make a roughing and a finishing pass, just to punish myself more...

My advice about cutting off is to use a carbide cut off tool and go through the hardened layer, and then finish the job in a band saw.

The idea of welding a side gear to a plate and using it for indexing was GREAT.

03-04-2005, 08:52 PM

Great pics and splines look great! I only need to extend the splines up the axles toward the flange maybe 3" so I will not be working with a bare round axleshaft and resplining per se'. I have a smaller horizontal mill and lathe than you but the vertical mills look about the same so hopefully I will be able to get the same results. My horizontal mill has an arbor and arbor support so I was looking for a round cutter that fit the arbor so that's why I was wondering if some type of keyway cutter would work. I have a small 8" X 29" vertical mill that has a power feed. Maybe I could use it instead of the horizontal mill. Any idea on what kind of endmill to use to cut these splines with? Do they make a kind of dovetail or tapered endmill that might cut the 30 degrees needed? The axles fit a 35 spline Detroit Locker so I would assume Moser cut the splines to a factory dimension, 30 degrees. I really appreciate the photos and insight to what is needed to accomplish this task. If you have any ideas on how to do this in a vertical mill, please reply here. Thanks again, emj.

03-04-2005, 09:44 PM
Thanks. I pursued that project for several years before finally getting set up to do it.

If you are going to cut the shaft hard (sounds like you are), you can pretty much forget high speed steel. The shaft you are working on is most likley 1541H and it is probably hardened to RC 35 or maybe even harder. It is hardened everywhere but the flange. HSS won't touch it.

The included angle is 60 degrees, so you'd be looking for a carbide end mill with a 60 degree included angle and 1/64" radius on the tip to match the fillet at the root of the spline. I wonder if you could get one custom ground? It wouldn't last long, but it might get you through a couple shafts before it needs to be re-sharpened. Or maybe not. I have no experience with that, I'm just speculating. I usually get a couple shafts out of the inserts before I index them, that's my only point of reference.

The easiest thing to do would be to get that same cutter I use and hold it in 3/4" collet in your vertical mill. I'm holding it in a NMTB50 to R-8 adapter with an 3/4" R8 collet in the horizontal. I sold that little Bridgeport and got a Gorton that is much larger and more rigid. I'd just put the cutter in a B&S9 3/4" collet if I ever needed to do the job on that mill.

The carbides are very brittle and they break if you touch them to the shaft while the cutter is not spinning. It seems to be nearly impossible to try to center up a spline in the tip of a carbide without breaking it off. This is going to give you difficulties if you try to index using a carbide insert and the original spline, but you probably could get through it this way and you'd need nothing more than the cutter, V-blocks and hold down stuff.

03-05-2005, 01:32 AM
Ahhhh, now we're getting somewhere. I like the carbide end mill with a 60 degree included angle and 1/64" radius idea. This has the most potential for me. I have an 8" Hartford vertical/horizontal indexer. Add that to the old spider gear axle holder/indexer and I may be in business. My "big" mill is a 3hp Bridgeport clone that I haven't used yet but the small vertical mill with the powerfeed does work so I may use it. I have yet to install the 3 axis DRO kit but now would be a good time to do so. I also bought a big(8,000lb) Lagun cnc vertical mill a year and a half ago but have never seen it because it's too big and heavy to fit in the garage. A friends parents own a fab shop in the next state over so it's been there running everyday. I bought these mills I have now because the Lagun is fully cnc, no manual operation at all. I have played with Mastercam waiting for the day when I can finally use the Lagun. At least now I can do a search for the elusive end mill thanks to your help. I have been trying to find cutter/how to info on this subject for quite awhile but only received where to get axles resplined but not how to do the work. Once again, I thank you for your time and pictures of your setup, emj.

03-05-2005, 02:04 AM
I just finished cutting a spline to adapt a shaft to a transfer case input. I ground the tool by hand, carefully comparing it's profile to the existing shaft, and then flycut the splines on a horizontal mill in a dividing head.

It fits nice. I haven't hardened it yet - we'll see how that turns out, but the point is: flycutting can work.


03-05-2005, 02:07 AM
To add to the last post, and answer a couple questions - the splines were involute, and the shaft definitely required softening.

It did not respond well to turning with carbide, so I knew that HSS would be hopeless.

03-08-2005, 09:57 PM
I found a company that sells carbide chamfer cutters with a 60* included angle and have a .010" tip for vertical mills. With this end mill, you would be milling from the top of the axle. They also sell carbide double angle cutters with 60* included angle but they cut at 1/32" not 1/64". With this cutter, you would be perpendicular to the axle or cutting at the 3 or 9 o'clock position. I may see if they can make a 60* included angle 1/64" tip carbide chamfer cutter, emj.

03-08-2005, 10:14 PM
I'm sure you can make either work, but what happens if it chips or goes dull during the cut? How much are you out? How long does it take to get a replacement?

If those options are real cheap, they might be OK for a one-off job. If you are starting to approach the $150 price of the cutter from DD Machine, or if you plan to do more than just a pair of shafts, buying a cutter that takes comon TPG 321 inserts might be more economical.

03-08-2005, 11:44 PM
The TiCN coated carbide chamfer cutter is $17 and the TiCN coated 60° double angle cutter is $35 so I may try them. I bought 50 TNMA433 inserts awhile back. Will these also do the job or are the TPG 321 inserts the only ones that will work? emj

03-09-2005, 07:43 PM
I'm not sure about the TNMA inserts. The insert needs to be straight up and down when the tip is at the tangent point to the shaft, becuase you are making a forming cut. The included angle will be off if it is tilted. Positive rake inserts have built in clearance and can stand straight up at the tangent point, but a negative rake insert would have to be tilted to create clearance.

Also, I believe the last 3 in the 433 indicates that it has a 3/64" radius.

Let me know how it works with those cutters!

Mtw fdu
06-04-2012, 12:22 PM

I am a new member of this forum and have come across an article about spline cutting which may help you. Click on the link below and it will take you to it.

http://www.rodandcustommagazine.com/techarticles/1207rc_building_a_better_bow_tie_part_iii_the_boun ty_in_the_backyard/index.html

Hope this helps.

Mtw fdu.

06-04-2012, 09:39 PM
He has not been here since 2009.

Davo J
06-05-2012, 12:10 AM
I have never resplined an axle, but all the diffs I have worked on over the years including 9 inch diffs, the axle is held in by the bearing, so if the spline broke it wouldn't fall out.


Mtw fdu
06-05-2012, 07:10 AM
Thanks for that info. I didn't think about checking the date of the last post. :o

Mtw fdu.