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Use commutators for the last piece or so you can't get in. If you don't know how to use them, I'd highly suggest learning, as they come in handy on pretty much any puzzle. I'd suggest reading some of the posts in the How To, Guides, etc. forum, such as Chris Hardwicks 4x4 BLD guide, intro to commutators, Mike Hughey's 4x4 Centers BLD, etc. There are tons of useful posts on this forum, search them out. Good luck.

I don't get to the last couple pieces before solving with comms, do you Pat?

I'll solve the inside rings and as many other pieces I can get with just a couple more simple 3-move swaps. After that I'm all comms, and I solve either 1 piece at a time (1 per face) or two adjacent pieces at a time (only if there are two of the same adjacent pieces within both centers - I haven't looked into doing non-adjacent pieces yet).

There are basically 2 slightly different ways to do this, but they both follow the P Q P' Q' pattern. The difference lies in that Q can be an outer layer (a face) or an inner layer (a slice).

Basic examples on the 5x5x5 cube (in order to not confuse with non-standardized notation)

1. Q as an outer layer : r' u r - U - r' u' r - U' (written as P-Q-P'-Q')

2. Q as an inner layer: r U2 r' - u - r U2 r' - u' (written as P-Q-P'-Q')

Please also note that a sequence (p1 p2 p3 ...pn) inverted will be
(p1 p2 p3 ...pn)' = pn' p(n-1)' p(n-2)' ... p1'. This is obvious when sitting down with the cube, but easily forgotten when working on paper with notation

Of course cycling blocks can also be done in 2 different ways like described above (if appropriate). Very large blocks may show side effects, due to overlap. Feel free to experiment a bit with this!!

I don't get to the last couple pieces before solving with comms, do you Pat?

I'll solve the inside rings and as many other pieces I can get with just a couple more simple 3-move swaps. After that I'm all comms, and I solve either 1 piece at a time (1 per face) or two adjacent pieces at a time (only if there are two of the same adjacent pieces within both centers - I haven't looked into doing non-adjacent pieces yet).

Hey Alex. I can always get down to 1 or 2 pieces left to swap (on each of the 2 remaining faces), then I use a comm. to do a 3 cycle with those 2 pieces, or 2 comm. to get all 4 pieces solved. I always do my last 2 centers adjacently, and the comm. are pretty easy for the most part. I build all centers by building 1x5 blocks mainly, and it works pretty good I think. There may be a better way to do this, but I want to practice it a lot before I try something else.

I downloaded the cube program from GabbaSoft.com and solved the 7x7 a few times over the past couple days. Here is my method of doing the last few center cubies on the final 2 adjacent centers.

Orient the cube so the 2 bad centers are on the F and U faces. Now turn the F and U faces so that if you were to perform an f slice, the bad cubie on the F face would move to where the bad cubie is on the U face. Lets indicate "f" and "r" as the slices that identify the bad cubie on the U face. Now look at this sequence:

U (r f ' r ' f) U ' (f ' r f r ')

The purpose of the initial U is to move the bad cubie on the U face safely out of the way. The (r f ' r ' f) moves the bad cubie on the F face up to the U face where it will want to belong. Next, the U ' puts the bad cubie back into position on the U face. Then (f ' r f r ') brings that bad cubie down to the F face where it belongs.

Hey Alex. I can always get down to 1 or 2 pieces left to swap (on each of the 2 remaining faces), then I use a comm. to do a 3 cycle with those 2 pieces, or 2 comm. to get all 4 pieces solved. I always do my last 2 centers adjacently, and the comm. are pretty easy for the most part. I build all centers by building 1x5 blocks mainly, and it works pretty good I think. There may be a better way to do this, but I want to practice it a lot before I try something else.

pjk, what is your typical time for centers? I use the exact same method as you, so I'm curious how fast you are with it. It takes me 6 to 8 minutes typically at the moment - way too slow, but I don't know how much of that is my recognition and movement, and how much is the method.