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Secondary centre bolt....?
Got me confused there Paul (I hope this isn't making it worse for you leinid!)
I have a Bintel 10" dob and once I've used the sec's centre bolt to centre the sec in the focusser I "fiddle" the 3 screws (actually bob's knobs for me) to set the (sec's) position. Of course, in adjusting the centre bolt in the first place to get the sec mirror aligned under the focusser, the 3 screws needed to be loosened (backed off) - from how I'm reading your post leinid these 3 screws are too tight to even loosen: this shouldn't be so, unless they are "factory set" with a drop of paint on their threads or whatever. You need to initially loosen them to fiddle with the centre bolt if that's your desire: they shouldn't be too tight to loosen unless they've frozen accidentally, or deliberately as above...
If you do loosen them to play with the centre bolt (for aligning secondary under focusser tube) they should then be tightened up after this so that the secondary alignment re focusser tube is correct - in practice this means "fixing" the 3 set screws to hold the secondary in the position that has the secondary concentric within the focusser tube outline and the oval secondary mirror appearing to be as circular as possible.
Once the 3 screws at the back of the secondary have fixed it in this alignment then the primary is "worked" on. Having said this, you will need in all probability to go back and tweak these 3 secondary screws again after playing with the primary's screws and then after that fiddle with the primary screws again also - you will find in the reiteration of this process that the 3 secondary screws will appear to be much tighter: they will have much more limited adjusting capacity unless the spring for the centre bolt is particularly weak.
Hope this helps you leinid - if you found one of the spider legs was bent and you've straightened it then I guess you really do need to adopt a "whole procedure" regimen to get everything correctly aligned. As Paul says, someone showing you is far better and easier - your local astro society/club would be very helpfull in that respect.
Cheers, Darryl.
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