Paper filter stamp for Picopresso stock basket

i recommend that you use the included 3mf project file. i had to drop the z coordinate of the outside rings down a little to cut off the bottom and make them hollow rings. if you use the STL they will have bottoms and be hard to use and the center puck could get stuck.

now for an explanation of what this is and what it's for. some people choose to use a paper filter disc in the bottom of an espresso basket for various reasons. the stock basket that comes with the picopresso is an odd size. the top of the basket is 51mm which allows you to use standard 51mm paper filters and/or puck screens on top, but the bottom is an odd non-standard dimension, something like 46-47ish mm. the edge is rounded/filleted so it's hard to say exactly what the inside diameter is because it depends on where you measure. the smallest espresso coffee filter i could find is 51mm, if something the correct size for this exists as a buyable product then i'm not aware of it. 

now enter this tool. there are scrapbooking tools you can use to punch a circle out of paper, and you might be able to find one in the correct size but this is for people who 1- want something that can be made right now for pennies because you have a 3d printer and it takes 20 minutes to print this vs buying a circle punch for 10 dollars which is also a much larger and less portable tool and you're frugal and shipping could take some time, and 2- this offers you the versatility of having slightly raised edges that hug the wall of the basket and follow the inside fillet of the bottom corner if that is something you find desirable. a possible benefit of this is that when stirring the coffee with a WDT tool, a flat loose filter could shift around when touched by the needles and get grounds between the filter and basket. it is maybe possible this crimped type filter could contribute to channeling but that is up to your own discretion.

if you want to cut the edges to have a round normal style filter, you can either cut around the sharp bent edge with scissors or if you need more guidance you can press it out so there is a slight edge and draw around that edge with a mechanical pencil or a pen or fine marker if you're comfortable with those inks being in your coffee brewer and then cut along that line. personally i would recommend just using the pencil, as pencil lead is made of only graphite and clay which are both inert and non toxic.

included are two outer ring sizes. one is pretty tight and is suitable for tracing a circle around the edge for trimming into a plain circle filter. the other is slightly looser and is good for making the rimmed type of filter, which fit best if the rim sticks out a little bit to hug the basket wall, then it will stay put better while you WDT, so the looser fit ring doesn't crimp the corner quite as tight which creates a less square angle for the crimp. you could use this tool to adapt aeropress filters to this basket, although i think it would be wise to trim the sides because aeropress filters are so much larger. if there is a risk of channeling along the edges, the taller the rim, the greater the risk, i imagine. the filters i'm using and are in my pictures are 51mm brikinte filters which as far as i can tell are the same thickness of paper as aeropress. i do not know how these will work with thicker filter paper. if you want to use thicker paper and the thicker ring is too tight, increase the X and Y dimensions of the larger ring by 0.5mm and fine tune from there.