Photo misleading; those aren't the same applications.
The left one is a common design for the nut that holds a CV axle shaft in place through the wheel bearings, and it isn't just Kia (and Hyundai by extension), it is very common. What isn't shown is that after installation, you stake the nut in place (over notches in the end of the shaft) to lock it in place.
The right one is how my trailer wheel bearings are. And motorcycle rear axles.
Couple key differences. Left one can be torqued in place and locked in position wherever it ends up. Right one, you are stuck with increments where the holes line up. Left one is usually (in all that I have seen) in designs where the bearing preload is set by the bearing inner races being clamped together. Right one is more suitable for old skool separate tapered roller bearings where you set the preload or clearance manually, which might mean the nut isn't all that tight. In the CV shaft design (left), that nut spins with the wheel. In the trailer-wheel, motorcycle axle, and non-driven wheel designs that use a stationary stub axle and a nut with a cotter pin, the nut and cotter pin are not rotating.
Both are functional, but only if properly tightened.
Less installation labor cost probably for the fancy flanged locknut on the left (although it looks like maybe the thin outer shell will be dented into a keyway on the axle.
Torque and dent.
Material cost of the mundane castellated nut and cotter pin (shown I think on a vintage tapered axle without the wheel hub ) is probably less if a standard thread size.
The old fashioned castellated nut on the right would be more useful for adjusting a wheel hub using bearings that must be "set" for a slight axial clearance.
Out of favor these days for modern non-driven wheels that seem to have swung towards the non adjustable angular contact cartridge with about 100 kmile but maintenance free service life.
I'd label the "KIA" nut as typical in modern times.
If the thread pitch is 20 TPI and the shaft has 2 holes (giving 6 possible angles for the nut) you have increments of 1/120" = 0.0083" axial clearance = approx' 0.001" radial clearance.
Tapered roller bearings are set in axial clearance. The 1-3 thousandths rule applies to every case I have come across with shaft diameters ranging from 1 inch to 12 inches. The axially locating pairs are in the same housing so there is no accommodation for thermal expansion.
I crunched this out for my Dana 60 hubs on another forum recently. I measured 12.3 TPI using a ruler. The locking washer has 16 holes but it's reversible for 32 positions. That gives 0.0025" per position.
On the other hand automotive hubs with brakes tend to have a lot more clearance than that, as expansion of the hub during mountain descents will eat up all the clearance.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
Taper roller bearings have a longer service life and other benefits with the correct pre-load. Lots of applications use a pre-load in the bearings. Machine tool spindles are pre-loaded. Pinion bearings in differentials are pre-loaded. I understand some big highway truck operators are using pre-load in their wheel bearings these days too.
Automotive wheel bearings are often angular-contact ball bearings nowadays, and normally the preload/clearance is built into the inner races which are designed to be clamped firmly together.
Not a BOLT, both are nuts.
The NON Kia is the best design. The Kia design is a one time use only, the NON Kia is multi use, and much better locking.
The automatic machines spit them off so fast cost is not an issue. Only to the end consumer that way over pays for everything.
And what Tugboat mentions is accomplished best by the Mercedes type axle nuts that clamp. Old 50's US cars and trucks and some newer used the castle nuts and accomplished preloads or clearancing close enough.
