Turin SD40 / iTop40 Stepless MOD.

The Turin SD40 is a good entry level grinder, but it's major draw back is the relatively large stepped grind size adjustment locking mechanism. 

This worm drive and dial gear replaces the original and allows for stepless grind size adjustment. 

In addition, the worm drive and adjustment knob assembly can be depressed to disengage from the dial gear, allowing quick large grind size adjustments.

The Turin SD40 is sold in other parts of the world by different brand names. Most commonly as iTop40, MiiCoffee d40, Starseeker 40mm, and Xeoleo 40mm. 

PSA: Miicoffee has recently released a stepless version of the Turin SD40 called the Miicoffee D40+ for $200. This version renders the Turin SD40 and the SK40 obsolete… and this mod. ; )

https://miicoffee.shop/products/miicoffee-d40plus-single-dose-coffee-grinder

Additional Parts needed: (be sure to select the correct size)

(2X) 4x7x2mm  ball bearings.

https://www.aliexpress.us/item/2251832775717315.html

(2X) 4-40x1/2" hex head screws. 

https://www.aliexpress.us/item/3256804480978574.html

Printing notes: 

Print slow, especially the first layer. 

35mm/s at the slicer, than reduce that to 35-45% at the printer, as needed.

.1mm layer height.

80% infill.

Main Dial Gear: Print with the slotted side down with support ‘touching build plate’ only. The geared portion does not need supports.

Worm Drive: Print with base end to the bed standing upright. Support is only needed for ‘touching build plate’. Print slow!

Worm Drive Frame: Print upright with legs touching the build plate. Recommend blocking the  undercut support for the upper half of the frame. It is not needed and will result in a cleaner print.

See photos for undercut blocking reference.

Adjustment knob: Print facing down with gear portion on top. Support for ‘touching build plate’ only.

Shims: Two are needed. One at the base of the worm drive, and the other, at the screw side of the adjustment dial. 

The 2 ball bearings allow for smooth dial adjustment, but  the pressure from the grinding force can cause the worm gear to rotate and severely throw off the grind size if there isn't enough resistance. Be sure to test and tighten the two screws as needed to apply the necessary resistance.

Inserting the Worm Drive into the Frame is tricky. With the ball bearing seated in the frame, insert the head of the worm drive at a 45* angle, horizontally and vertically. this will require a bit of wiggling.