Your photo is of a simple spindle, not a drive axle. The keyway in your photo is for holding the thrust washer from spinning, which keeps the bearing from riding against the spindle nut.
I'm not sure who you are responding too, but, I agree, most early model vehicles used a single keyway rear axle shaft and a corresponding hub to match. It's just that your photo was not of that setup. In most of these designs, the axle shaft was tapered so the hub was wedged tightly onto the axle shaft once the axle nut was torqued to it's proper setting. Also, in most cases, the hub and drum were an assembly, not one single piece. The drum was mounted to the hub and either riveted together or the studs were pressed into the hub and then staked to the drum. Chrysler had some of their early designs just the opposite. They pressed the stud through the drum and then staked it to the hub. Either way, if the drum was ruined or beyond specs, it could be replaced without having to replace the hub also. That saved some cost. The earlier VW type I, II, and III were an exception. Their rear hub and drum were one piece and were replaced as such. Everyone of those I worked on from 1955 and newer used a multi-splined hub......no keyway. It also wasn't a tapered setup. I worked on some of the '54 and earlier VW's too, but, so few of them that I don't remember having the rear brakes apart on those to give you any info on how they were designed. I'm sure you can look it up if you're itching to find out.
I'm not sure who you are responding too, but, I agree, most early model vehicles used a single
keyway rear axle shaft and a corresponding hub to match. It's just that your photo was not of that setup. In most of these designs, the axle shaft was tapered so the hub was wedged tightly onto the axle shaft once the axle nut was torqued to it's proper setting. Also, in most cases, the hub and drum were an assembly, not one single piece. The drum was mounted to the hub and either riveted together or the studs were pressed into the hub and then staked to the drum. Chrysler had some of their early designs just the opposite. They pressed the stud through the drum and then staked it to the hub. Either way, if the drum was ruined or beyond specs, it could be replaced without having to replace the hub also. That saved some cost. The earlier VW type I, II, and III were an exception. Their rear hub and drum were one piece and were replaced as such. Everyone of those I worked on from 1955 and newer used a multi-splined hub......no keyway. It also wasn't a tapered setup. I worked on some of the '54 and earlier VW's too, but, so few of them that I don't remember having the rear brakes apart on those to give you any info on how they were designed. I'm sure you can look it up if you're itching to find out.
