Comments from my life, family, and projects I enjoy.

Sunday, June 9, 2013

Hobart Coffee Mill, Grind Chamber and Motor

The motor and grind chamber of the Hobart 3430 has now been disassembled and cleaned. After a week of soaking with PB-Blaster, the fixed burr remained stuck fast in the grind chamber. With only a small edge of the burr exposed to push against, I was reluctant to apply a lot of force for fear of breaking the burr. I carefully applied heat to the burr with a heat gun. Once the burr was too hot to touch, I applied more PB-Blaster and observed the heat draw the solvent into the parting line. A gentle push against the edge of the burr and it popped free.

The fixed burr after removal

The grind chamber without it's burr

The grind chamber and fixed burr after clean-up

The grind chamber is also the end bell for one side of the motor. Once the grind chamber was removed from the motor, I was able to remove the rotor assembly and the other end bell containing the start circuit.

Centrifugal Start Switch. Note flyweights and actuator disc on rotor shaft.

While I had things apart, I replaced the motor bearings and cleaned things up a bit. The original bearings were New-Departure C8503 and C88503. Both have an extended inner race, so make sure you measure the critical dimensions carefully before ordering replacements. I bought my replacements from Accurate Bearing. They are always super helpful with obtaining the obsolete types and had these in stock. Below are some pics of the rotor before bearing replacement. Note the grooved piece to the right of the bearing. The parts diagram list this piece as a seal. I have never seen anything like it before. There were no remnants of rubber or oakum in the grooves, so I'm not sure how this works. I think one reason for this design is to provide a surface for the adjustable burr tension spring to ride upon, as it rotates with the shaft and adjustable burr. After cleaning everything up I placed the seal back on the shaft with a little Locktite bearing retainer and reassembled.

Rotor as removed with fan, bearing, and seal

Each motor subassembly was cleaned up and repainted before final assembly. I've included a few pics of the completed assembly.

As a routine part of any restoration of old equipment with a capacitor start motor, I always replace the start capacitor. The original capacitor was mounted using a large strap clamp attached to the lamp bracket. The entire assembly bolts to a standoff bracket inside the case. The new capacitor is much smaller and mounts with a different style mount, so I fabricated a new bracket from some scrap I had in the shop.

Original lamp bracket with strap clamp

New lamp bracket with replacement capacitor mounted
Thats all for today on my grinder project.


Buttons said...

Wow I bet you can fix almost anything.

Scott said...

It's what i love to do.

Anonymous said...

hi, Scott,

could you say where you found the replacement capacitor, and how you cleaned the metal parts?


Scott said...

I cleaned up all the parts with a wire wheel in the drill press, sandpaper and some scraping with various sharp tools in the tight spots. The capacitor is a Dayton motor start capacitor from WW Grainger. 88-105uf/220-250 vac. Grainger number E224674.

Anonymous said...

thank you for that information, Scott. we'll try Grainger.

actually was meaning to ask what you used to clean the grind chamber and burrs? so far, I've only removed the assembly that is on the back of the grind select handle. lots of 80 year old coffee dust pasted into the metal parts.... used some mild soap, warm water and a toothbrush. that coffee paste is sticky!

Scott said...

The coffee oils turn the dust into a sticky rancid paste. Any mild solvent will dissolve it away. Kerosene, lighter fluid, or WD-40 will dissolve it away. The grind chamber and all parts inside the grind chamber are cast iron so don't be afraid to have at it with a wire wheel. Summertime is here and I'm totally involved with home repairs and gardening so the grinder will wait until the dog days of summer or next winter.


Mark Moore said...

You used a WW Grainger. 88-105uf/220-250 vac. Grainger number E224674 its has for post, I have the same grinder and mine only has 2 post. what two post did you use?

Scott said...

Hello Mark,

The new capacitor actually has only 2 terminals, but there are 4 post for push on connectors for each terminal. Once you have it in hand and look at it it will be obvious.


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Midlands of South Carolina, United States
Husband, Father, Quality Engineer, Electronics Professional, and tinkerer. Facinated by old technology and well made old tools. Old iron is good.