Reddit reviews uxcell Metric Thickness Feeler Gage Gauge (0.02-1.00mm)

Pick up a cheap feeler gauge on Amazon. .2mm works for me most of the time, and it's really easy to feel when you've got the spot. Link

Ok. I now have an understanding of your problem. To restate for those that were as confused as I was:

The bed is NEITHER level or trammed. Instead OP is relying on the "auto bed leveling" wherein an end stop or the nozzle is probed at several XY positions on the bed and then this information is used to offset the build accordingly.

Honestly I've been opposed to this method since people started doing it on RepRaps a few years ago. I believe I've seen discussions of doing what you would like to do previously in the reprap forums but I could not find anything with a quick search (http://forums.reprap.org/). As stated elsewhere you'd only really need 2 adjustments, but that's still 2 more motors you need to control and they only need to be controlled at the start of a print.

It seems like a huge increase in complexity when the same effect can be achieved with 3 screw knobs once a month. That doesn't make it any less interesting and I encourage you to try it out. An added complexity here is that Josef's Mendel moves the table in the Y-direction, so now you have to move those motors too.

Just in case this helps you, here is my tramming method:

1. I use a .1mm feeler gauge instead of paper. I heat the bed to the operating temperature first. I run my printers leveling script (you could just jog the X-Y axes around) and slide the feeler gauge in at each of the points. I adjust until there is friction but the gauge isn't stuck. Ensure that your nozzle tip is clean first!
   
   
2. If any one of the knobs required more than 1 turn of adjustment I do it all over again. This time all the movements should be smaller and have less of an effect on the other positions.
   
   
3. I run one of WHPthomas's interactive leveling prints. These basically print a 1 layer object. As it is printing you can adjust your bed until everything looks good. The nice thing here is, your build surface is warm and you're laying down material to ensure tram.
   
   This whole process takes at most 10 minutes. Once it's done I can print confidently for at least 100 hrs of print time (about 2 weeks for us).
   
   If you need to substantially change temperature settings, retram. I don't typically switch materials all too often though. Cheers.
   
   Feeler gauges: http://www.amazon.com/Metric-Thickness-Feeler-Gauge-0-02-1-00mm/dp/B0052IRYVS/ref=sr_1_1?ie=UTF8&qid=1427385860&sr=8-1&keywords=.1mm+feeler+gauge
   
   WHPthomas tramming prints: http://www.thingiverse.com/thing:39430
   
   

About Calibrating a Delta, I'm using this wizard to calibrate mine and I've got to a point where I can't seem to get better than [-0.1:0.1] offset on all 7 probe points. I'm using 6 factor and [a gauge like this](uxcell Metric Thickness Feeler Gage Gauge (0.02-1.00mm) https://www.amazon.com/dp/B0052IRYVS/ref=cm_sw_r_cp_apip_WJL7ivK8ztXUi) using the 0.1 mm sheet to measure the height between the nozzle and the bed.

How do I know when to stop?

To add to /u/ntoff's idea, feeler gauges make great shims. Find a metric set like this and cut the 0.5mm shim with some tin snips and then wrap it around the stepper shaft.

Feeler gauges also work nicely.

Pick up one, like here, get the scope set in the rings, find the right point in the gauges where any thicker and it won't freely slide between the scope and the mount, then tighten. After you have your rings torqued down, you should need to remove the gauges using some force, but your scope will be mounted perfectly level with your mount.