I mounted the larger piece of linear slider to top of a 1X2X1 C-channel. I mounted two pieces of 3X5 plates (cut from 25X5 plate) to sides of C-channel. I mounted bearing blocks to plates. I put a 12-tooth pinion gear on a square bar inserted through bearing blocks. The gear mesh is too tight and hard for me to rotate the square bar. I didn’t want to use a motor because I would destroy the motor clutch. I know of new gear brackets but the rack gear bracket goes under the larger piece of linear slider and if I want to mount the larger piece of linear slider to the C-channel, I will have to use pieces of 1-wide bar between the larger piece of linear slider and the C-channel. I would file the holes on the plates so that the gear mesh is not too tight. Which should I do - buy gear brackets or file holes on plates?
Perhaps the first thing to do is complement your (good) explanation with a picture or two - I can pretty much visualize it all using your description; but I confess that I have a hard time thinking of alternatives (that will make the 12-tooth spur gear align with the rack) without being able to see a picture or the real thing.
If the only alternatives you want to explore are the ones you listed, buy the brackets and figure out how to adapt your plans to their size.
I attached a picture to this message. Even after pushing the plates up as I tightened the nuts and screws, the gear mesh is too tight.
Try loosening the screws holding the pieces of 5x25 plate and pull them up just a little.(usually there is already a small gap in the square holes so they will shift a little.) Pull them up as far as they will go and see if it helps.(unless you already tried this, or maybe it won’t help.) It might not shift enough to pull the gears apart much.
(That might have been a little confusing.)
Have you tried rotating the C-Channel so that the slider assembly sits inside the channel (in a valley) instead of outside of it (on top of a hill)?
The pictured configuration is the “on-top-of-the-hill” config.
Have you tried widening the platform supplied by the C-Channel and then building your spur Gear’s mounting fixture on top of the wider platform.
I have two ways of widening it in mind.
Attach some short peces of C-Channel along each side of the one shown in your picture. Build up from them using stand-off beams or other pieces that don’t have to attach to the side holes in the C-Channel.
Put a piece of plate on top of the C-Channel and attach the slider, rack, etc. on top of the plate. Again you will not be slaved to the location of the holes in the side of the C-Channel.
I tried putting the slider assembly inside the C-Channel but screws that fasten the plates to the C-Channel got in the way. I was able to push up the plates as I tighten the screws fastening the plates to the C-Channel. I guess I don’t have to buy the gear brackets.