I'm afraid that while many 'scope operators swear by "Bob's Knobs", many swear at them for the very reason you mention : i.e. they don't hold adjustment. (On a personal note I can't judge. I had a set made up for me in the UK some 10 years ago but, working on the principle that "if it ain't broke, don't fix it", I never fitted them to my old Nexstar 8i OTA).
But as to replacing them once again with the original screws, it goes without saying that each "Bob's Knob" must be replaced "one at a time".
I'd propose therefore that you set up the 'scope pointing, (if possible) at Polaris and remove one of the "Knobs". Replace it then with the original screw and follow Rod Mollise' "Rough" collimation instruction.(See below). Carry out the same operation with the replacement of the other two "Knobs" and once all have been "roughly" brought into optical alignment, you can then begin with the refinements.
Here's Rod's link:
Hoping this helps,
PS. If you wish to attempt the operation in daylight, you can of course use a pukka artificial star or failing owning one, a Christmas bauble, strategically placed beyond the minimum focusing distance of your 'scope, (25-30yds.?) to catch the rays of the Sun. This should give a similar effect to a star. If you use this technique though, do make your final fine adjustments using a real star of about the second magnitude. (e.g. Polaris).
Edited by Tel, 07 December 2016 - 03:41 AM.