3018 DIY CNC: T8 Leadscrew / Anti Backlash / Spring-loaded nut Spindle Head

In addition to my revision of the drive transmission of the Y axis (see here and there), I have also revised the holder for the spindle motor so that backlash-free T8 spindles can also be used with it.
In addition, there is a cam for triggering optional limit switches on the Z axis. The limit switches can be attached to the right side of the X-axis part of the holder.

Instructions from version 1.0.4
The fumbling with the M3 nuts annoyed me. In addition, the spring may be blocked on these cheap, ragged nuts, but their full functionality depends on the ease of movement of the spring. Therefore, from version 1.0.4, I did not attach the spindle nut with M3 screws AND nuts. Instead, the nut is now attached with 4 M3x15mm screws. If this is too unsafe for you: Put a drop of superglue in the M3 hole, this will keep the M3 screw bombproof. Please check beforehand whether the M3 thread also fits ;-)

So when the spindle nut is where it should be, you put the spring on the nut from the other side, push the lock nut with the two webs into the recess in the spindle nut and then turn the TR 8 spindle through both nuts. If it runs smoothly and without great resistance and the lock nut does not turn, you are almost there: You can repeat the last step again in the Y-axis bracket.

For people without ambition with endswitches I have also added a version, this is the "development branch" ** a **, recognizable by the letter "a" at the end of the file name.

All others use the version ** b **.

Photos follow, I first have to print out the part myself.

Instructions up to version 1.0.3: Screw the T8x100 spindle a little into the spindle nut, but so that it does not go beyond the slot. Put on the spring and position both through the large hole of the holder. Now you insert the lock nut from the other side against the spindle nut so that the two lugs protrude into the slot, but only as far as you now screw the T8x100 spindle into the lock nut until it is held. Just look at the photo.
On the first photo you can see how the spindle nut is properly preloaded. In the end, it must also sit in the spindle holder.
Now use the tweezers to fumble an M3 nut into one of the hexagonal recesses and screw the M3x20 Allen screw through from the other side. Do this with all 4 screws. Now remove the T8x100 spindle, but make sure that the lock nut does not come off, it is best to hold it with one finger. Place the spindle holder in the X axis holder of the 3018 router. Push the T8x100 spindle through the floating bearing and screw it through the preloaded lock nut to the spindle nut. The spring must move freely and press the lock nut away from the spindle nut.
Now you can connect the T8x100 spindle to the coupling of your NEMA motor again.
The spindle nut and the lock nut must be clamped into each other so far that the TR8 threaded rod runs without play and smoothly! If the threaded rod is difficult to turn, you better open the tension around a thread.
And by the way, you can now pull your finger away from the lock nut.

You need:
1 perfectly calibrated printer. The holes for the IGUS bearings
are designed for a press fit (15.1mm), while the bearings have a 15mm Diameter. Otherwise you may have to ream the 15mm hole or glue the bearing into, if the hole is too big.
1 x 100mm TR8 Rod and anti-backlash leadscrew with spring
4 x M3x20mm Head Socket Head Cap Screws
2 x M3x25mm Head Socket Head Cap Screws
6 x M3 Nuts
1 pair of tweezers to place the fiddly M3 nuts, if you have sausage fingers like me.

Optional:
Some Makerbot Endswitches. For assembly suggestion see last photo.

To do List:

Extension for focal point laser measuring system with line laser

History:
2020/02/05: Internal Version 1.0.1 with first Tests
2020/03/01: Tolerance for IGUS bearings slightly increased after printer recalibration. Tolerance for IGUS bearings slightly increased after printer recalibration. The bearings were too tight at a colleague's printer.
2020/03/05: Public Version 1.0.3. Some minor changes to make screwing the spindle nut easier. This is the final version in this branch of development.
2020/03/08: New photo from version 1.0.3 placed in 1st place.
2020/03/09: Version 1.0.4b. Simplified assembly of the lock nut: No more M3 nuts required. Threads for fastening the spindle nut with 4 M3x15mm cylinder head screws are also printed.
2020/03/09: Version 1.0.4a: Version without a cam for triggering optional limit switches.
2020/03/10: Smaller dimensional changes: Distance between spindle bore and Z slide increased.
2020//03/14: Version 1.0.41a: Smaller dimensional changes: Some spindle nuts apparently come with larger springs. So I expanded the 13mm hole to 13.5mm. Some spindle nuts apparently come with larger springs. So I expanded the 13mm hole to 13.5mm. More makes no sense, as otherwise the M3 screws for securing the nut will no longer find sufficient hold.

Some of the links are suggestions for parts to replicate the thing and affiliate. If you buy something, I get a small commission. The price you pay is the same. Thank you very much.