Gearbox splines internal and external

[Col21Participant @col21]

[Col21Participant @col21]

Hi there

Ive got an external splined shaft that’s stripped the splines. Was thinking to machine a new spline shaft but would it have to be hardened after machining. It’s about 100mm diameter by about 150mm long about 30ish splines. Also the hub splines it locates into has stripped about 5 splines of it. What type of welding rod would one use to build back up to remachine.

[SillyOldDufferModerator @sillyoldduffer]

I don't know! The late, great John Stevenson did this sort of work but it's out of my league. Anyone else into repairing splines?

Dave

[Clive FosterParticipant @clivefoster55965]

Google is probably your friend here.

Did a quick search with building up splines with weld as the text and got a number of useful hits from reliable sites

Only one I looked at was a thread on the MIG Welding Forum titled Spline Repair. Nice thing about MIG Welding Forum is that its UK based and (usually) doesn't call out anything uber hard to get over here.

Start Quote from one reply

You don’t want to use anything too exotic like SuperMissileWeld which is basically just a jumped up nickel rod.

Either 309/312 if you think the original shaft is a hardenable material.
Or just go right ahead and weld it with ER70s2 TIG or 7018 stick

End quote

Clive

Edited By Clive Foster on 08/05/2022 19:48:51

[John ATTLEEParticipant @johnattlee20632]

What machine is it for and do you know what caused it to fail. Is the hardening to resist the wear or to increase the strength? How come only five internal splines are stripped? I would have expected it to be all or none! Is the shaft 150 mm long or is that just the length of the splines? How long are the internal splines? What is the form of the spines?

John

[HopperParticipant @hopper]

Driveshaft for a 10 ton truck? Or agitator drive for a washing machine? Could make a difference with rod choice.

[duncan webster 1Participant @duncanwebster1]

If a new one would have to be hardened after machining, so would a built up one. At least with new material you know what it is, what it's current state is, and how to harden/temper it

[Bill Davies 2Participant @billdavies2]

Col21, since there are a lot of splines, I guess they are vee or involute, probably the latter as these can be hobbed like gears.

So, if you plan to machine one, you might check for curved teeth.

Bill

[Col21Participant @col21]

[Col21Participant @col21]

[Col21Participant @col21]

[Col21Participant @col21]

The spline shaft is about 99mm diameter with 44 teeth. Could I use an involute cutter for this? Never used one before and if so how do I know which one to buy? As in the photos it’s roughly 3.3mm deep, can this be cut in one pass. I’ve got a Bridgeport mill and dividing head so easy enough to calculate the revolutions.

[DC31kParticipant @dc31k]

Posted by Col21 on 10/07/2022 17:45:20:

Could I use an involute cutter for this?

You could use an involute spline cutter if you knew the specification of the spline.

An involute _gear_ cutter would be totally unsuitable.

You will need to research what specifcations of involute spline exist in the world (metric-speaking places are likely to have a different spec. to imperial-speaking). If you are lucky, there may be software that will draw the candidate profile for you so you can print it out at 1:1 scale and compare. Possibly, Gearotic will do it.

[old martParticipant @oldmart]

Its a bit big for a model, smaller splines than that are used on helicopters to transmit thousands of horsepower.

[Pete RimmerParticipant @peterimmer30576]

That's a 2.25 module gear in the picture. Being 6" long I guess you could call it an involute spline but essentially it's a long 2.25MOD involute gear.

It would be quite easy to cut with a gear cutter on a mill but since you say the internal mating part is also damaged you won't be making one of those in the home shop, not easily anyway. That's gear shaper/wire eroder work.

[DC31kParticipant @dc31k]

Posted by Pete Rimmer on 10/07/2022 22:19:45:

That's a 2.25 module gear in the picture. Being 6" long I guess you could call it an involute spline but essentially it's a long 2.25MOD involute gear.

It's a good observation on the relationship between OD, teeth and module, but that does not necessarily mean it can be called a gear nor can we infer that a gear cutter will form the tooth spaces correctly.

Splines have different geometry to gears, specifically the relationship between pitch diameter, addendum and dedendum. In particular, spline teeth are considerably shallower than gear teeth. In a way, they are roughly analogous to a stub tooth gear profile (I think Fellows had one, designated, for example, as 6/8). As for pressure angle used on splines, we would have to do further research.

There is a set of softwate called MITCalc, which offers a spline module for 14 Euros. Even if a person did not want to buy that, the documentation for that module tells you what you have to measure to identify the spline.

[John HinkleyParticipant @johnhinkley26699]

Posted by Col21 on 07/05/2022 18:22:54:

Hi there

Ive got an external splined shaft that’s stripped the splines. Was thinking to machine a new spline shaft but would it have to be hardened after machining. It’s about 100mm diameter by about 150mm long about 30ish splines. Also the hub splines it locates into has stripped about 5 splines of it. What type of welding rod would one use to build back up to remachine.

Can we re-establish the actual dimensions of the piece? In your original post, you state that it is 150mm long, but the piece that you show being held is clearly a lot shorter. Possibly 15mm? Or have you sawn a slice off the end?

I only ask as it will be far easier to machine if it's the shorter length. A picture of the stripped hub splines – if that is what they are – will help to address the other part of your question. I regret I have no solution to you, but as you have seen, there are others better qualified than me who have.

John

[HopperParticipant @hopper]

Splines are not the same as gear teeth, necessarily. There are various standards for splines, separate from gears, including ISO, DIN, SAE and BS. Among those there are then straight-sided splines, serrated splines and involute splines. Then among the latter can be any of a number of pressure angle involutes ranging from 14.5 degrees to 45 degrees.

Some clue as to what this gearbox is out of would be helpful. 10 ton truck? Or washing machine? Made in which country? Made when?

Another way you can do it is weld it up and make a fly cutter to match one of the undamaged splines and use that to recut the same profile on the welded bit. Rods to use depends, once again, on what the application is. How many horsepower will it be transmitting? At how many rpm? For how long and how often?

Cutting the internal splines could be done in a slotter or shaper, depending on the length of the spline required.

[Brian WoodParticipant @brianwood45127]

Be a little careful about re-cutting spines on a shaft. I saved some damaged Landrover 1/2 shafts for stock material where the splines had been stripped off. The damage went well below the surface in the form of fatigue cracking following the spline face angle and I found in the worst case I had to machine off about half the diameter to get down to clean material.

It was safer altogether to cut the splined length off completely to be able to use the bare bar as source material

Regards

Brian

[not done it yetParticipant @notdoneityet]

He’s a bit cute re info – location or finer details.

I might guess – but only a guess – is it is on the JCB he was enquiring about, earlier.

I might guess that it is something on the axle drive – to accommodate articulation or track adjustment maybe?

JCB diggers can come in a wide range of sizes/power.

[HOWARDTParticipant @howardt]

If it is a JCB or similar vehicle you may find it is a rolled spline not a cut one. A big difference in torque capability.

[BazParticipant @baz89810]

Come on Col21 tell us what it is used for or what vehicle it belongs to, if you want help please tell us the full story.

[Pete RimmerParticipant @peterimmer30576]

Posted by DC31k on 11/07/2022 06:26:31:

Posted by Pete Rimmer on 10/07/2022 22:19:45:

That's a 2.25 module gear in the picture. Being 6" long I guess you could call it an involute spline but essentially it's a long 2.25MOD involute gear.

It's a good observation on the relationship between OD, teeth and module, but that does not necessarily mean it can be called a gear nor can we infer that a gear cutter will form the tooth spaces correctly.

Splines have different geometry to gears, specifically the relationship between pitch diameter, addendum and dedendum. In particular, spline teeth are considerably shallower than gear teeth. In a way, they are roughly analogous to a stub tooth gear profile (I think Fellows had one, designated, for example, as 6/8). As for pressure angle used on splines, we would have to do further research.

There is a set of softwate called MITCalc, which offers a spline module for 14 Euros. Even if a person did not want to buy that, the documentation for that module tells you what you have to measure to identify the spline.

It's possible but I would bet my hat that it's a 20PA gear profile just going by the photos. It would take some decent measuring to find out but a simpler method would be to print the profile generated by geardxf and stand the gear on the print. It would be obvious right away.

[BazParticipant @baz89810]

Oh well six days have gone by and Col21 doesn’t seem to want to share with us. I am concerned that unless we get the full story regarding his post we can leave ourselves open to trouble if things go wrong. Where exactly do we stand legally by recommending a material or process. A bloke on the forum said it would be ok etc. Maybe I am overthinking things, maybe when this heat goes away I will be back in workshop and working rather than thinking.

[John ATTLEEParticipant @johnattlee20632]

We are not providing professional advice under a contract. Unless we were grossly negligent, I cannot see how there can be a problem. If one of us did give such bad advice it would only be a few micro seconds before we were shot down by someone else on the forum.

John

[Author]

Posts