Help please. Dip switches and mach 3 settings

[dazp1976]

Hi. Happy new year! I know it's february, but after holidays and furniture orders, I just managed to get back to the cnc project last week. Hope you are all well.

So I took the whole thing apart, removed the wooden frame it had underneath, bought some steel tubing and made a new support for the cnc.

I managed to get the rails coplanar, with the two strings method, and a cheap usb microscope.
I have used a straigh edge to do one rail on each axis, then by moving the gantry, got paralel the second. It took a while but it worked.
Today I got the y and x square with the 4 holes method. All methods, mentioned in this thread, so thank you everyone.
I only have left the ballscrews allignement.

Reassembling the cnc, I noticed there were some screws loose. It might be that I did not tighten them in the first place, or they came loose while the cnc functioned. Anyway, I used only bolts and plain washers, and it might be not good enough, so I intend to upgrade this with something else, before I get the cnc working again.

Doing a bit of reasearch, I found a few option, the best one being crazy expensive. Some nord lock washers. But still there are a few which might work. Tab washers, safety wire, and locktite (I do not like this idea, as I am not sure if I can unscrew the thing). It might not be a must to upgrade all the bolts, but some for sure, like the ballnut bracket ones.

What do you use in order to prevent screws from coming loose due to vibration? And is it a must to use any special type of bolts, or the cheap silver one will do?

I use tensile bolts with either spring or serrated washers. Where I need nut & bolt I use nyloc nuts.
No bolts have came loose.
Examples:

https://www.ebay.co.uk/itm/SHAKEPROO...qgg:rk:10:pf:0
https://www.ebay.co.uk/itm/M2-M2-5-M...OicKyTw5sf01Co
https://www.ebay.co.uk/itm/M4-M5-M6-...ID805KSc9mzpls
https://www.ebay.co.uk/itm/A4-STAINL...nSZw:rk:3:pf:1