Vintage Hand Grinder Restoration
So, you've picked up an old hand grinder, maybe at a yard sale, a thrift store, off ebay, or from Grandma, and it looks a bit beat up, a little worse for wear...but you know these old mills have a reputation for being really good coffee grinders! What to do? And how do you do it? We hope this short primer will serve as a guide to help you put your old mill back in service!
First & foremost, one must address the mechanical condition of the grinder. If you look up, inside the body, though the drawer, and see a big 'fur ball', don't worry - this isn't unusual! Years of coffee accumulation, and is a good sign that it worked well enough for someone to have used it. The wood case might be a bit bruised, chrome needs polishing, but basically, both the appearance & function can be improved through some simple restorative procedures.
We are working with a Zassenhaus Zenzi in this restoration. It's kind of a different Zass, varies from the usual dome top models a bit but the general restoration procedures are the same for all coffee grinders.
First, we open the box (if you have a dome top, it's generally held on by four screws through the top). On this grinder, there is an inner frame held in by a screw through the back, which we removed, and - what the hey? The top still won't come off! Fiendishly, there is another screw, hidden under the metal name tag on the front!
Remove that screw, and the entire metal top & mechanism lifts off!
Remove the nuts (or screws, as is commonly the case) that secure the bottom bracket. This allows you to slide the burr away from the wood, grab the shaft with a needlenose vice grip, remove the top crank shaft cap nut, and while holding the vise grips, turn the handle off the shaft.
Release the vise grips, and all the parts can now be removed, along with a few decades of stray coffee bits. (We have also seen cloves, peanuts, walnuts, peppercorns, and a few things unidentifiable!)
The simplest way to clean the burr, and all the metal parts, is to soak it in coffee cleaner (we use Joe Glo), soak it overnight at least.
In this case, the drawer was quite stained with coffee residue, so we scrubbed the drawer with Joe Glo, rinsed it & dried it as fast as possible, and then blew it out with compressed air to make sure the glue didn't soften.
After soaking the parts in cleaner, scrub them off with a brush, and rinse well. Inspect to see if they need further cleaning by either soaking, or cleaning with a pick. Dress the burr axle with steel wool (just polish it up a bit - they can sometimes be a bit rusty at the top bearing.
Dry all the parts well, and set them aside.
Now it's time to address the box. Inspect the box carefully and note any problem areas. Think about what is your goal? The old mills often have a very nice, warm, nutty, patina. That patina is lost if you refinsh the box. What is the condition of the Varnish? Are there gouges? Scratches, dark spots, thin areas? How do you want it to look? Some problems, such as light, small scratches that can be fixed using Scratch Cover. This is the restorerrs dilemma - what you gain in perfection, you lose in character. You may decide to just clean the wood, oil it, polish the chrome, and enjoy the mill! There are many directions to go, depending on your goal.
In this case, the finish is not 'warm & nutty", it is dingy. There is a large area of varnish missing on the back of the box. Numerous small gouges & dings on the sides. The drawer is missing some varnish, and has quite a few knock-about marks.
What tips us toward refinishing on this grinder is that it has a metal tag. If a mill has a decal on the box, you are almost guaranteed to lose the decal if you refinish the box. With a decal, you may just opt for a touchup instead of full case restoration.
We've decided to refinish the box on this grinder. First, remove the old varnish with paint stripper (we use liquid stripper because we like it better than gel or paste stripper).
After refinishing, and after it is completely dry, inspect the case for cracks or loose joints. On this grinder we needed to glue a partially opened joint on the bottom near the foot. Use any good glue for crack or joint repair. Clamp it, and let it dry thoroughly.
This was a simple glue repair, for more complex cracks & separations you may need to use 2 or 3 clamps to align & hold it while it dries, and you may need to do the repair in stages - first one crack or joint, then another. Once the box is nice & solid, everything glued up tight, go over the box with fine sandpaper, using a hard sponge sanding block. Pay particular attention to the corners, since now is when you can get rid of most, or all, of the unsightly dark spots & bruises. Use increasingly fine grades of sand paper - you can spend as much time on this aspect as your heart desires - it will only get smoother, and cleaner (always sand WITH the grain).
Clean off the sawdust with a tack cloth or compressed air. You will need to use some type of stain to bring up the color in the wood. For this mill we used Golden Oak stain.
When the stain is dry (usually overnight), go over it with fine steel wool.
Clean it well - we used compressed air. Finish it with clear lacquer (we use spray lacquer from the hardware store - if you're talented you can use a brush!) Be sure to mask the parts that you want to protect from the lacquer. We stuff the box with paper. With spray lacquer a few thin coats is preferable to attempting one thick coat of finish. Hold the box in your hand, mist over one surface while holding the surface horizontal, turn the box, do the next surface, etc. untill all 4 sides are nicely glassed over with a thin coat. Be sure to watch out for drips (if you do get drips you can rub them out when the lacquer is dry). When the finish is dry & hard, rub it down with fine steel wool, then give it another very thin coat. Repeat this process till you're happy with the result.
Now we polish the metal. If you're lucky you have no chrome loss, no rust, and no scratches - in that case you can just take a cloth, and metal polish, and shine it right up. We use Happich Simichrome for this task. If there are no scratches in the chrome, be sure to use only a dry, clean cloth & metal polish. If there is an oxidized build up you will need to polish with fine steel wool & polish first, followed by polishing with the cloth. On the Zenzi we had lots of chrome loss on the handle, darkening of the metal, as well as pitting of the chrome on the doors, and some light rust. First we used fine grit wet sandpaper to remove the pitting & rust from the doors.
This was followed with fine steel wool & metal polish to work out all the surfaces till they were smooth to the touch on both the handle & the metal top. There is a lot of elbow grease involved in this step. After the steel wool, we use a cloth & metal polish - this brings out the luster in the metal, the handle was polished in the same manner, steel wool & cloth).
If the funnel has chips or discoloration you may want to give it a quick coat of spray paint to spiff it up. Be sure to clean it in coffee cleaner, then wipe it down with lacquer thinner, then paint.
Now that the box is refinished, and the metal is all clean & polished, the burrs are clean - it's time to reassemble the grinder! If not much time has passed, you will likely remember how it came apart...but, if your memory is short - take pictures as you go along - they can be invaluable (as was the case with the Zensi!). Give the box one last inspection inside & out - check the braces, make sure you don't need to do any more gluing or repairs to it.
Now we reassemble the grinder. First assemble the burr, before attaching the bottom bracket apply a bit of grease into the hole on the bottom of the inner burr. This grease is trapped inside the bearing & doesn't come into contact with your coffee.
Attach the lower bearing strap loosely. Insert the axle shaft through the top bearing of the metal dome. While holding the mechanism with the burr up, turn the burr with your fingers while watching, and listening, as well as feeling it - you want to make sure the inner burr is aligned nicely with the outer burr. It should have an even feel, and sound (if not centered the sound will be louder on one side, than the other, or sound as though it has 'skips").
Reposition the outer burr slightly if needed until you feel & hear that you have a centered alignment. Now, tighten the adjusting cam all the way down, until it locks the burr. Visually examine the mating of the inner & outer burr - it should be even on all sides.
When you feel confident that the outer burr is in the right place, tighten the nuts or screws tight, as the final securing of the alignment.
With the burr locked screw the handle onto the shaft. Install the top cap nut by holding the handle in one hand and using a wrench on the nut. Reattach the top mechanism to the box by whatever method your grinder uses (the Zensi uses 4 screws to attach the wood to the top, then 2 screws, 1 in the front, and 1 in the back).
Replace the metal name tag.
And, you are done, except for the all important test run!
When the burr is clean, your first grinds will 'condition' the burr. Set the adjusting cam about 1/2 turn counter clockwise from burr lock. Drop some beans in the hopper & see what happens - in the case of the Zensi, it turned out to be a very nice espresso grind.
Overall we are pleased with the results of this restoration - the chrome couldn't be renewed, but it the steel and the remaining chrome has been brought back to a nice luster - rust removal & polishing made a big difference. The wood separation is no longer problem, the oak case has a nice glow, and an even semi-matte finish, with very nice contrast between the end grain on the side pieces and the blonde in the center. And, it turned out to be a very nice, very clean, functioning coffee mill.
This was just one mill out of many. We have not covered all of the issues that can come up with these little beauties - other problems such as broken or missing parts, enlarged nail or screw holes, broken screws, warped bottom boards, broken or partial drawers, dents in the metal parts, handles that will NOT come off, bent handles, deep gouges in the wood etc. Most of the problems with the boxes are dealt with as general woodworking issues, most of the issues with the burr are cleanliness, and alignment.
We hope this short documentary helps you in approaching your grinder project.
Please NOTE - we don't sell our hand grinders on ebay!