Brown & Sharpe Valumaster 612: what do these knobs do?

I bought a B&S Valumaster 612 Surface Grinder last week and got it set up over the last couple of days. I don't have a manual, and I've not yet found one, apart from the reprints available from the company who took over these machines after B&S closed its doors. (I will probably go ahead and spend the money for a reprint, but it won't be here for a couple of weeks.) Most of the controls are self-explanatory, but I don't have a clue about the function of knurled knobs on each end of the carriage. Also, I am thinking that the mag chuck handle is showing signs of severe wear, but I'm not sure how much slop is normal. Any help will be appreciated.
One more question: The carriage control 'swing handle' seems a bit unusual. Most photos of this model show a micrometer dial, like the other axes. Was this a B&S option?

optoeng said:

the function of knurled knobs on each end of the carriage.

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On my Mitsui, that's where the wire rope drive for the X motion is anchored, and the threaded end adjusts the wire tension. Generally need to disengage both ends to lift the table off. Not certain if it's the same on your B&S, but would be slightly surprised otherwise.

Also, I am thinking that the mag chuck handle is showing signs of severe wear, but I'm not sure how much slop is normal.

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Of all the permanent mag chucks I've used, over half of them were broken at that location and field-fixed, and most of the rest were at least as badly bent/worn as that one. Slop doesn't matter, really, but I recommend you fix it before it breaks, because it will break just when you trying to get a job on or off the grinder.

Many thanks for your quick reply. It seems likely you're correct about the function of those knobs. I'll refurbish the mag chuck lever right away.

Thanks for your reply.

Looking around the web, I have most often seen the type of wheel shown in the attached photo.

If I remember correctly the two knobs when backed off will provide enough slack in the band so you can reposition the long handle if grinding near the ends of the chuck.

Thanks for that helpful addition.