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I find out that suplied screws for end stops not work very well for me, since they have rounded head, and when the machine homes fast (for example in Rpetier software, i slowed down second pass) there is situations when end stop arm sits in different position on the screw, depending on speed and other factors. This can give you inconsistent Z LENGTH, and problems with calibration.
So I made new hole with thred for M4 screw. I moved it away from the aluminum extrusion, this way itąs not interfere with belt clamps on the cheapskates. I rotated end stops and make new holes for them.

When doing it i don't have long enough M4 screws with flat head, so I made my screws from the M4x60mm, I machined rounded top and put 2 nuts under head. I don't use suplied screws because I don't have more imperial nuts at the moment.

This gives me two things:
1. More acurate homing and leveling, since and stop sits in the same spot in the center of flat head. It's not sliding over rounded head.
2. Now i have better control over calibration, since i don't use screwdriver to screw/unscrew from the top. I use wrench, so I can better tell how many degrees I twist my screw.

Evertything looks like this:

the screws weren't threading into the plastic very well for me. I took a narrow piece of aluminum and bent it into an L bracket drilled a hole for the screw mount, and a hole to mount it on the carriage using one of the belt clamp screws (stacks up like a washer). I tapped the hole holding the screw, and put a jam nut to keep the adjustment from vibrating loose and moving homes.

So far so good anyway, i'm still calibrating (2days build, 2 days mods/tweaks to get to first print, and now 1 day of printing cal blocks and pyramids). I have to travel m-f generally. I think after calibration prints i need to do just a touch more bed leveling,my head is low tword the z, and about right at the x/y and i think my nozzle is too small. I'm running repetier software. Adjustments i had to make from the repetier max software were motor home directions, diameter parameter for "bed leveling" when you had a low or high center. Running repetier .80 but thinking of trying cura.