Background

This thread documents reassembly of the Bunn LPG brew grinder fitted with Ditting 804 burrs to convert it into an excellent cupping grinder, a project that began with Cannonfodder's servicing instructions for the Bunn LPG and osanco's burr mount adaptor. Others have referred to this type of Bunn grinder upgrade as a "Bunnzilla," but that name describes Ditting burrs installed in the taller Bunn grinders where the frames are sometimes shortened. For simplicity's sake I call mine a BunnDitting.

Bunn LPG Characteristics

The Bunn LPG is a high output coffee house grinder in a small package that fits under a kitchen countertop. There's another model that has divided hoppers for regular and decaf coffee, the Bunn LPG-2E. LPGs are still readily available used, at low cost. I found mine in decent condition for $75. At more than $320 the Ditting Burrs are nearly as expensive as one of these grinders new (about $500 for the grinder). Steve Green's (osanco's) adaptor is $80 as I write this, plus shipping. Because the LPG is designed for coffeehouse use, the hopper is meant to be mostly filled. It lacks a narrower bean feeding chute that would ease small dosing for home use. There's abundant popcorning (spraying stray grounds) under the cover that I work around with a long handled paintbrush to slide stray bits into the feeder. At my own risk (and yours if you choose this) I've removed the wire finger guard for easier brush access. The brush works well with the finger guard in place. I may eventually create a feed pipe but other projects need completion.

Summary of Disassembly and Cleanup

To start I removed the hopper, separated the motor assembly from its base plate and separated the bottom stand from the upper part of the grinder. I then was able to get at the burrs and remove them. The burr mounting screws were badly caked in old coffee grounds. Dave's (Cannonfodder's) teardown went farther than mine did. I left the motor shaft in place and didn't disconnect wiring and was able to clean the parts that make contact with the daily grind. I had to scrape out the slots and apply heavy pressure with a handheld screwdriver to turn them out. NB: With any screw subject to getting stuck, glued by residue, corroded or rusted I apply Loctite Food-Safe Anti-Seize compound before threading it back in. This should make it easier to remove for servicing. Alternatively I recommend any lubricant that's not going to contaminate edibles, such as DOW 111 silicone lubricant. I then immersed the burr mounts in strong JoGlo solution, taking care not to fully immerse the upper burr mount shaft because this part can rust. A half hour later I rinsed and wiped these parts clean and applied a thin coat of Loctite's food-safe anti-seize compound to those parts that could rust. I also used paper towels soaked in dip-it solution to finish clean-up of these and frame parts and wiped those clean with water before drying. This general approach is summarized in Dave's thread. From here reassembly begins with many pix to follow.

Reassembly Documented

Mounting plate for top burr.



Top burr in its adaptor bracket, back and front.





Top burr in place.



The bottom burr is spring-loaded. It has a brass bearing that falls out when it's facing downward, so I'm working with the motor assembly on its head. Here you see that bearing being put in place. The goop inside is silicone lubricant.





Next I went to mount that bottom burr. Proper bench technique (PBT) involves photographing disassembly and labeling all parts. This looked so easy I winged it and almost made a serious error. I used the wrong screws to remount the upper burr. This may not have caused a problem on that burr but would have been disastrous on the lower burr, which is spring loaded and is held in place as it rotates by a bottom plate. Without following PBT it's easy to be misled. The mounting screws that come with the Ditting bearings are bigger than the Bunn mounting screws. I thought I corrected this by choosing narrower screws but was mislead by the length of the Ditting screws.



You can see the longer screws protruding from the mounting bracket. I spotted this and fixed it.

Here's the bottom burr from underneath, with the shorter screws mounting it.



Now the bottom plate goes in place. It's easily pushed down because the spring isn't very torqued to get it in position. It's just firm enough that the adjustment screw works.



It has two gaps where coffee grinds could easily enter the upper assembly. These are sealed with flaps and brackets, held in place by small screws.

The motor with burrs mounts on a bottom plate that holds the electronics.

Here it is in place.



With mounting screws attached.



And now upright.



It sits atop the base via 5 vertical mounting screws mounted here. Inserting the screw on the back right (topmost arrow) is tricky. On my machine an electrical component partly covers it, so it's easier to insert the screw, let the bottom dangle and attach that to the base first. Then position the base over the other mounting holes, insert screws and attach. A needlenose pliers is useful if you have trouble positioning this.

During reassembly I noticed a feature I hadn't scoped out before. This grinder has a timer that can be accessed with a removable lid on the back.



To continue reassembly I finished fastening the top half of the grinder to the base with four side-mounted screws.



Then it was time to reattach the motor cover.





I was nearly done and realized the rubber pads on each side had come loose when the old glue degraded. I found the right glue but the tube was partly dried. Probably more than a few of you have excavated what's left by puncturing the tube!



Finally I reattached the bin without the finger grate (at your risk, remember?). Take care when reattaching the bin. The fastening screws can get loose and find their way into the grind chute, which of course happened to me! I had to upend the grinder and recapture that !#&* screw.



And was able to place the grinder on my new counter.



I'm using it for a BraZen brewer, Clever Drippers and such. I place the metal coffee filter in the center of the Bunn brew funnel and use that as a catch cup for pouring the grounds into whatever brewer I'm using. (My grinder was missing the brew funnel, and I found a new plastic one for about $10 online.) Some fines adhere with static to the metal filter, which creates an even cleaner brew after transfer. I tried it this morning and had some tasty cups. It'll take awhile for these blades to break in, so it will get even better.

I may do some mods in the future, including creating a bean feeding chute, using the old cover top with a hole drilled in it to position a clear plastic pipe. I may also do another documented mod to add a lever to the adjustment screw.

Marshall,

Thanks for the deli tub suggestion. Right now it works pretty well with a swipe of a paint brush. If I do mod it for popcorning I'll want a finished look and will also want to seal the irregularity on the lip where the beans feed into the burrs. Since we're still unpacking our house it will be awhile and that brush will get some exercise.

Hi Dave,

I had a kitchen bowl under there at first. Some grounds were going astray. I haven't had static problems with the plastic Bunn brew container. Some fines collect on the metal brew sieve I insert from the BraZen brewer but I empty those into paper anyway. What I like the most about the clip-in container is it doesn't leak any grounds or dust from the top. That clip-in was under $10 shipped so it's easy to sort out preferences.