being a lurker for a while, I decided to write up my recent experience on modding a Bunn. Since most of the information and ideas was read from here. It's time to contribute.

This is the finished mini Bunnzilla, I even forgot to take a picture before chopping it.


Things to share:
**Stepless** my Bunn (2nd hand bought) came with a healthy bearing. So it was very minimal force transferring to the detent plate. After taking off the detent plate to confirm the knob could hold itself, I fill up the detent hole with epoxy to keep the limiter function and put it back. I done it with the original detent plate. Not the Trifecta one. Alternatively you could remove the spring loaded screw, the one touching the plate. But it needs a large flat head screw driver and I don't have it around.

**Shortening** despite the very clear and well written Instrustables guide (hat off!). I didn't take off the middle section motor when I shortening the lower half. It saves a lot of time. The base drip tray front was removed. The base was reinstalled after the shortening in reverse. So that I don't have to worry my ugly hand grinding works. (I'm just a weekend warrior mechanic). The base is a rigid structure, it should be kept. I believe I read it somewhere saying it's not necessary.

**Lower section notes** As you can see from the final picture, it was a pretty aggressive height reduction. The lower section also the home for the large capacitor and others electricity stuff. I've to make some rearrangement to fit everything in there. In the end, I've to ditch the original capacitor holder and have to duct tape it on the base. (sorry, no picture....wasn't thinking about writing at that point)

**notes on reattaching** The shortened lower section was reattached to the base thru rivets. If I have the chance to do it again. I will use something serviceable. Since the opening at the back is now too small to reach any electricity stuff inside.


**burr alignment** Let's face it, it's a bulk commercial bulk grinder. When the EK is able to make good fortune out of a misaligned burr, never expect the alignment is good on a Bunn. Before the alignment, I wasn't able to choke my espresso machine with the finest. I could do it after.

**burr alignement steps - my way**. I sanded just the chamber with three 220 grit paper by following Scott's blog guide. I sand it by basically following everything outlined in the blog except the hand turning bit. I used the grinder's motor instead, by holding the shaft cap with a thick gloved hand. It takes ~15 second to finish a sandpaper. Yes, it sounds scary but I know what I'm doing and the glove I was wearing is a real heavy duty one.




**burr alignment - carrier sanding?** I decided it's good enough and didn't move forward with the carrier sanding. I think it's good thing to do, but the gain should be minor once the chamber is sanded perpendicular to the carrier/shaft.

**how it taste**, I didn't try it with the original burr so no comment on that. Comparing it with my Sette 270 on espresso, the astringent are gone with the same 1:2 ~30 sec pull. On brew (V60), the TDS reading is much higher on the same visually judged grind size. (comparing with my 1Zpresso hand grinder and the "ghost teeth"). The taste is just way cleaner and sweeter. Blind tested by my wife and she agrees.

**final notes**, I live in Hong Kong and it's not cheap/easy to get hold of a 220V version of Bunn. Adding the cost of the SSP burr, It's not cheap at all. But given the joy of modding and being able to learn how things works. I think it's worth it overall.

Hope it helps the next "mother of the dragon"!

HB Posts/external material being used for reference:

MiniBunn: Shortened Bunn G1 instructions [FAQ]

Adding fine adjustment screw to Bunn/update

80mm SSP burrs

New Burr Option for Bunnzilla - SSP

https://www.scottrao.com/blog/2019/1/9/ ... ur-grinder

I've had a 'bunnzilla' for a few years but never spent much time on alignment outside of some modest foil shims. Needless to say I can't get fine enough for espresso. Reading this is tempting me to do more... if only I had the extra time and no small children.

Devin H wrote:I've had a 'bunnzilla' for a few years but never spent much time on alignment outside of some modest foil shims. Needless to say I can't get fine enough for espresso. Reading this is tempting me to do more... if only I had the extra time and no small children.

The way I sand it down by using the grinder's motor should be faster than the whiteboard-marker + foil shim. It toke me 2,3 hours, most of the time was used on cleaning the spray adhesive actually.....which could speed up if I've it better prepared with some hard nylon small brush.....

Great write up, thank you!

Could you please post the links to the references that you mentioned in your write up? (Burr alignment, shortening, etc...)

Bmccall wrote:Great write up, thank you!

Could you please post the links to the references that you mentioned in your write up? (Burr alignment, shortening, etc...)

I edited the original post and added a reference section to the end of it.

JohnB. wrote:The original Bunnzilla which uses Ditting burrs has never had a problem grinding fine enough for espresso but there isn't a lot of adjustment range. After your sanding/alignment how much adjustment do you have in the espresso range?

IMHO, the adjustment range is dictated by the adjustment screw TPI. The burrs design shouldn't able to alter much. On the Trifecta numeric plate, I'm not able to pull a shot at the finest dial setting 1 (<20ml after 1 min, close enough to call it choking?). Currently using the range between 1 1/3 and 1 2/3 to pull a normal 1:2, 25 sec shot. I'm still on the first week using the new setup though.

The Bunn, being designed for a bulk grinding purpose got the limited range curse with its ~12 TPI screw. The adjustment plate is just ~170 degree range. When you compare it to the EK43, which is ~350 degree range adjustment. What it means is a much higher TPI screw to provide a finer adjustment per knob rotation degree.

posts I read the ~12 TPI:
Adding fine adjustment screw to Bunn/update

I'm still considering the above fine adjustment screw idea. I think a better way is modding it into a ~350 degree range adjustment. A CNC screw conversion ring (stepping up the TPI) and a new adjustment screw should do the trick. Going to follow up on this idea if I'm not able to have a good experience on the dial setting control in the coming weeks. (I'm a roaster and my mini-bunn needs to be changing adjustment everyday between brew and espresso grinds.)

Don't mean to highjack the thread:

Also recently built a Bunnzilla from G3 using redspeed coated SSP burrs.

Spent some time shimming with tinfoil and dry erase marker. I think I am close, but after aligning and re-calibrating (barely rubbing right at 1): V60s don't taste good at all. However, I haven't seasoned.

Did you guys find that seasoning made a difference?

According to Jonathan, who runs coffeeadastra.com, he saw about a 10% improvement in consistency after seasoning: https://www.google.com/amp/s/coffeeadas ... ity-2/amp/

I replaced my stock burrs in my G9 with SSP silver and have a marked improvement. I have not done seasoning (I don't have pounds of stale coffee and I'm not willing to waste other food products for seasoning).

Can you be more specific about 'not tasting good'?