My first mod doesn't have a bling or cool factor. What I wanted was to be able to change the MK2 bit easily in between jobs, or even in the middle of a job without having to remove the material or remove any components. So far, this mod has worked like a champ for me-but I'm not going to go out and say it is the best way to achieve the same results.

With this mod, I am able to park the Y at a specific spot. Lift the Phlat lid and drive the Z so the collet is just above flush with the table surface of the printer. Then I depress the mechanism button in in the back of the printer and turn the collet so that it locks in place and the mechanism button "gives" about an millimeter. This allows me to wrench the collet to release the bit and change it. After the change, drive the Z down and then jog it back to x,0,0.

EASY-PEASY!



My parts (from memory).

• Threaded rod cut to about 6.5"
  8/32 Lock nut for a knob
  8/32 hex nut for a stopper
  Washer
  Some bamboo skewers (2x1")
  Flanged bushing (rod should slide freely)
  1" Nylon stand-off (rod should slide freely)
  1/16th ply
  Spring

The riser is made from a piece of 1/16th ply. Two matching skewers pieces are CA'd to it to act as a support for the nylon stand-off. This is screwed in place on the inside of the MK2, right under the drive roller end cap.

The hole is 2 3/4in down from the top edge, and centered about 3/16th from the tab slot inward. Look closely before drilling and check it twice!


Thats it!

Now I can do a milling pass with the 1/8th bit, turn off the router, change bits, and then do a cutting pass with the 1/16th bit without removing the material (Which is held down with small soft canvas bags filled with BBs).

Just be careful to make sure your mechanism retracts before jogging the Y or Z. Be sure to jog the Z back first so that it doesn't drag across the material. Adjust the Z for its new depth to compensate for the differences in the bits. Remember to home the Z only! Attached files

 

Oh, I use EMC2 and not Mach. I don't know if you can type G codes into a console like interface inside of Mach but if you can, this mod should be doable.

my bit change code looks like this (assumes I have it homed on a specific spot on the table).
g01 z .25
g01 y 25.2
g01 z -1
change the bit
g01 z .25
g01 y 0

and then home the Z after you adjust it visually.