I'm sure that if you measured the old heavily rusted shaft spline teeth, you'd find they are way out of tolerance compared to a new shaft. Before installing the new slack adjuster, the tech simply wire brushed the old rusted spline shaft, smeared it with grease, and installed the new slack adjuster. It was rusted solid and no longer had a 'sliding fit' under any load conditions. I watched a video of how to replace one of these brake system slack adjusters, and the tech had to use a jackscrew puller and impact wrench to separate the 10C spline joint connection.

In reality, I don't think it matters much with the slack adjuster application being discussed. The SAE J499 standard describes a type C spline fit 'to slide under load', while the chart above describes a 10-C as a 'sliding fit when not under load'. Thread404-287612: SAE parallel tooth splines: RE: SAE Straight Sided Splines - External Spline Dimensions gearcutter (Industrial) 18 Mar 15 21:00 I've tried looking for dimensional data on brake cam shafts on semi-trucks/trailers but haven't found anything worthwhile.ĭoes anyone have any experience with dimensioning SAE external splines? The load cycles will be very low for this application as it is not a rotating assembly like a motor/pump. The splined length of the slack adjuster is 1.00'. The slack adjuster can apply ~2,300 lb*ft of torque max to the shaft. I don't believe the application is severe. The method and amount of 'breaking' sharp corners and edges also depend upon the conditions and requirements of each application.' SAE J499 makes reference to the shaft dimensions, but only states the following: 'The shaft dimensions depend upon the shape and material of the parts, their heat treatment, and methods of machining to give the required fit. I can not find any references to what the external dimensions of the shaft splines should be. I have a copy of the 28th edition Machinery's Handbook, but can only find dimensional information regarding the internal splines (specifically for broached holes). The slack adjuster mates to the shaft by a 1.5' - 10C SAE spline. The slack adjuster acts as a lever arm to rotate a shaft which engages the brake pad to the rail wheel. I'm designing an air brake system for a railroad application which will use automatic slack adjusters which are typically found on over the road trucks/trailers. After several years of referencing this website, I've decided to post a question I haven't been able to find an answer to.

Sae 6b spline shaft dimensions