Trim your own portafilter paper filters with this 3D printed cutter

#1: Post by **michang5** » March 18th, 2023, 12:14 am

TL;DR - I designed a circle cutter that trims AeroPress filters to fit a variety of portafilter basket sizes (55mm, 46.7mm, 50.8mm, 53mm, 37mm, 56.5mm, 45mm, 53.5mm, 58.5mm).

All files can be downloaded for free on Printables - https://www.printables.com/model/425608 ... -multiple-

If you don't know which size(s) you need, check out the images on the Good Brothers Coffee product page. If you don't have access to a 3D printer, consider buying from them.

Demo (of earlier prototype):

I can vouch for the performance and accuracy of the 55mm cutter. The trimmed filters are closer to 54.5mm and work great on the bottom of my 58mm VST 18g ridgeless basket.

The files for the other sizes are mathematically accurate, but UNTESTED. If a cutter doesn't work, please post a comment here or on Printables - preferably without giving me a low star ranking - and we can make adjustments together.

#2: Post by **GDM528** » March 18th, 2023, 6:48 pm

Nice work!

Have you considered posting an easily modifiable file format, like .step?

#3: Post by ab » March 18th, 2023, 10:16 pm

This is really cool! Can you cut multiples at a time or only one?

March 19th, 2023, 12:57 am

Thanks!

I was able to cut 3 with an earlier prototype. The current model has the blade 0.5mm lower so you might be able to cut 4-5 at the same time.

As for posting STEP files, I'd like to see how folks react to the STLs first. I'm kinda expecting to have to make some changes since reality always seem a bit different than mathematical accuracy.

#5: Post by **GDM528** » March 19th, 2023, 4:32 am

michang5 wrote:As for posting STEP files, I'd like to see how folks react to the STLs first. I'm kinda expecting to have to make some changes since reality always seem a bit different than mathematical accuracy.

In that spirit:

I'd suggest moving the nut pocket a bit deeper towards center to accommodate wider extrusions. For example, I use a 1mm wide bead and a 0.5mm layer height.

I'd also suggest a 0.5mm chamfer on the edges facing the build platform to compensate for any 'squish' from the first layer.

Have you tried designs with more than two blades - would that create too much friction? More blades (like, five?) would require less rotation to complete the cut.

#6: Post by **jedovaty** » March 19th, 2023, 10:44 pm

This is great! Are the base and spindle the same for all cutters, i.e. do we only need to print the center for multiple sizes?

March 20th, 2023, 12:34 am

The base has a single trough for the tip of the knives to travel through, but that's a good idea: multiple grooves in the base to accommodate different cutting diameters.

<my apologies to the OP for back-seat driving the very nicely designed models, but hey, other people do the same thing to me! >

March 20th, 2023, 11:42 am

jedovaty wrote:This is great! Are the base and spindle the same for all cutters, i.e. do we only need to print the center for multiple sizes?

Unfortunately, they are all different because reducing the cutting radius/diameter reduced the wall depth for the bolt to screw into. If you're like me and built your own Prusa MK3S+ printer, you likely have a couple of spare M3x12mm bolts from the kit. That's what I used to secure my blades. Regardless, the design should work whether you had 6, 8, 10, or 12mm length bolts. The flip side of that decision was reducing the center spindle diameter for each size.

As for the base, I could probably merge some or all of them into one master base with all groove diameters cut into it. My fear is that the filters would flex/collapse into a super wide groove. If folks want to guinea pig it, I'm willing to create and share one.

March 20th, 2023, 11:42 am

GDM528 wrote:The base has a single trough for the tip of the knives to travel through, but that's a good idea: multiple grooves in the base to accommodate different cutting diameters.

<my apologies to the OP for back-seat driving the very nicely designed models, but hey, other people do the same thing to me! >

No worries. I could probably merge some or all of them into one master base with all groove diameters cut into it. My fear is that the filters would flex/collapse into a super wide groove. If folks want to guinea pig it, I'm willing to create and share one.

#10: Post by **jedovaty** » March 20th, 2023, 2:47 pm

michang5 wrote:If folks want to guinea pig it, I'm willing to create and share one.

I'd be down for this, but maybe in a few weeks.. I currently don't have a 3D printer or access to one (my local libraries are also void of these for now), however, a friend of mine has a busted one that probably just needs a cleaning so I may borrow it for a bit later