Timken Bearing fit question

"End Float", usually measured in thousandths of an inch, means axial movement of a shaft of some sort. Probably the most convenient way to measure the spindle end float is to mount a dial indicator to your compound slide or QCTP at an elevation such that you can advance the carriage and bring the rod sticking out of the indicator to bear on the right end of the spindle. Move the carriage out of the way. Tighten either the threaded collar or the nut on the threaded rod until you think that you are close to zero end float. Then bring the indicator to bear on the right end of the spindle and while pushing the spindle toward the tailstock, zero the indicator. Push and hold the spindle away from the tailstock and any movement of the indicator will be the end float. Reduce the end float to zero by whatever method you are using and then tighten the collar 2 teeth of the spindle gear. Then check that the spindle is still free to turn but with a slight drag. This should all be done with all components at room temperature (~70°F). When satisfied with the preload, check and confirm that the brass or lead pellet is still present in the tapped hole(s) in the collar, insert and tighten the set screw(s). And finish reassembling the headstock.
 
Hello Abear. It looks like the interference fit of the inner race on the shaft is suspect. My reading of Fitting Practice Tables for taper roller bearings (both FAG and Timken) is that for an inner race of between 30mm to 50mm diameter the interference should be between 4 tenths and 15 tenths of a thou. An interference fit of 40 tenths of a thou seems way too high. You could check your bearing bore diameter against the published tolerances for tapered roller bearing in the catalogues (https://bit.ly/2Jsd3GG) and then work out what the shaft diameter should be.
 
Abear,

According to the Timken catalog that Ian gave the URL to and the copy of it that I already had on my local machine, the bore of the inner race of the Timken 14125A both Class 2 and Class 3 should be between 1.2500" and 1.2505". The unused example that I have here agrees with that. As best I can tell, it is bang on 1.2500".

However, if you are confident in the bearing preload applied, I wouldn't take it back apart. But just finish putting it together and use it.
 
no need to press on the left bearing on my 618, it's a tight slip fit but moves with some drag on the spindle.
 
Hello again Abear. Robert mentioned that the bore of the inner race of the correct taper roller bearing is 1.250, -0.0 +0.0005. And you have measured your shaft diameter at 1.2490. In which case the inner race should be a nice slide fit, but it isn't. Sooo, two questions spring to mind: is the TRB you are using the correct one and is the shaft diameter truly 1.2490?
 
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