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This model is specifically designed for the 1Zpresso J-Ultra Espresso Grinder. It is a replacement knob for the grinder handle that you can print much quicker and cheaper than you can order a new one online and wait on it to ship. I found that only after a few months of regular use, the original knob would sometimes slip loose and pop off the handle stem while using it. This slowly became more common until it no longer even snaps onto the handle at all. The handle stem shows no signs of wear so the inside of the knob must be an inferior metal alloy or a non-ideal geometry for the job and has failed from mild regular use.

I made this replacement knob cover a bit more stem than the original to give more to grab onto and less room for it to wobble loose. I also designed a tight snapping mechanism with relief pockets that are only possible with Additive Manufacturing techniques! This helps lock the stem into the knob very securely while leaving enough room for the knob to spin smoothly for regular grinder operation. Adding a tiny amount of lubricant to the inside of the knob before installing will significantly improve operation and longevity! You can use lube you may already have from other hobbies or projects; it just needs to be relatively thin, not dry out, and be safe to use with metals & plastics.

I recommend printing with dialed in supports that can easily be pulled free with some needle nose pliers. Scarf joint seams help hide the print seam better on the round surface. Recommended material is at least PETG, though something like ABS/ASA would hold up longer. I printed my test unit out of PETG several months ago and it is showing no signs of wearing out. Installation will be tight but this is intentional. You will know it is fully seated because it snaps into place and no longer comes off easily.

NOTE: Due to reverse engineering the model internals off a single end product with no reference to the original dimensions & tolerances, plus the new tolerances introduced by 3d printing this part, there's no way to guarantee this will fit your grinder stem. This will always be a concern when reverse engineering parts without original dimensions & tolerances. If your printer is dialed in, I think it will work for most people most of the time but I included the STEP file just in case you want to make an adjustment or possibly use it for another grinder handle. You can also ask me if you need any help!

Printed Weight: 22g + <1g waste

Additional Items: Designed to replace a lost, broken, or failing knob on the 1Zpresso J-Ultra Grinder. Might work with others, STEP included for modifications!

PRINTING:

• For best results, print from the 3mf
• Unfortunately the center hole most likely needs a support to print properly, dialed in supports are easy to pull out with any fine nosed pliers
• Print with scarf seam and at small layer height (~0.12mm) to achieve a good surface finish or use ABS/ASA and a vapor finish it for a truly polished look!

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