R8 Mill Holder tray

This is a drawer storage tray for a single R8 taper mill holder, with magnetic retention for both the mill holder in the tray, and for the tray to a steel surface (tool cabinet drawer usually).  There are already plenty of printable storage trays for R8 collets, but an end mill holder will usually slide, tip out, or not fit at all in these, especially if there is a tool installed in the holder.

This design features 4 magnets on the base to hold the tray in place, and one at the tail end of the taper to hold the taper in the tray.  There is a hoop over the tail end to prevent tipping out, but with sufficient clearance to allow easy removal or insertion.  Each tray requires 5 10mm x 3mm round N48 neodymium magnets.  I glued mine in place but this may not be necessary since the fit is designed to be very snug.  I have found the trays retain their position in the drawer, and retain the mill holders well unless the drawer is slammed open or shut. 

The tray is designed in Imperial units because those are the units of the R8 taper specification, and it was just easier to measure the metric magnets in inches than to try to do the taper in mm, so you'll have to keep that in mind when opening the model in your slicer.  This should be printed vertically on its tail.  I used PETG for these with good results.  Other materials may work, but I don't see a lot of point, and you may have to adjust for different shrinkage to maintain fit.

I hope somebody else finds this useful; a lot of trial and error went into the design before I got something I was happy with.

Edit 24JUL2023:  Here is a modified version of this tray, to take mill holders for ¾" shank tooling:

https://www.printables.com/model/535163-r8-mill-holder-tray-for-34-shank