OXO Pepper Mill: Fine Grind Adjustment

The OXO pepper mill replacing our worn-out pepper mill arrived filled with peppercorns and, during the ensuing nine months, we established its finest grind setting produced bigger pepper flakes than we prefer. I figured there had to be a way to get the ceramic stones just a little bit closer, even though it has no user-serviceable components inside.

So, we begin.

After rinsing out most of the pepper flakes (the remainder appearing in the pictures below) and determining the two obvious screws didn’t release the housing, the Jesus clip on the shaft extending through the peppercorn compartment came under consideration:

The washer beyond the clip bears on the black plastic spider. It turns out the thickness of that washer determines the distance between the grind stones at the minimum setting: making it thicker reduces the stone gap and produces a finer grind.

Knowing full well it would be impossible to get the clip back on the shaft in that position, I pried it off.

Spoiler: Don’t do that!

The grind adjustment lever turns the chunky black ring inside the gray housing:

Three protrusions on that ring step along notched ramps around the perimeter of the black spider in the clear housing on the right.

The shaft slides out to reveal the spring under the inner stone, with a second washer bearing against the bore of the gray plastic housing:

As a result, the spring tries to push the shaft and inner stone out of the housing (toward the left). The protrusions on the grind adjustment control how far the shaft can move, with the washer + clip locking the shaft to the spider.

Gentle persuasion extracts the chunky black ring:

The outer stone fits into a recess in the gray housing:

One might 3D print a washer fitting under that stone to close the gap between it and the inner stone, but the two screw holes interrupt the ledge enough to suggest the washer would be in two parts divided. If I didn’t have a mini-lathe, that’d be the best way to go.

But I have a mini-lathe, so I made a steel washer slightly thicker than the OEM washer under the clip:

The OEM washer:

• ID 6.7 mm
• OD 10.2 mm
• Thick 0.6 mm

Not knowing the right answer, I made a 1 mm washer, which is visibly thicker:

Which let me reassemble the pepper mill in reverse order, only to establish reinstalling the Jesus clip deep down inside the housing is, in fact, impossible.

Taking everything apart again let me contemplate the inner stone on the shaft, leading to the discovery it could slide very slightly on the shaft. More pondering revealed a slight seam in what I had taken as a monolithic black cap:

Applying gentle suasion between the stone and the cap with a plastic razor blade enlarged the seam into a gap. Much to my surprise, further prying popped the top off the cap:

Happy dance in full effect!

Removing the screw let everything slide off the top of the shaft:

Freeing that end of the shaft meant I could install the clip on the bench, add various parts while sliding the shaft through the housing, then tighten the screw to snug everything down.

As with most activities, it’s trivially easy when you know the trick.

Whereupon I discovered the new 1 mm washer jammed the two stones firmly together at the finest grind setting, so the correct washer will be somewhere between 0.6 and 1.0 mm thick:

• Back to the lathe for a 0.8 mm thick washer
• Dismantle pepper mill
• Swap washers
• Reassemble
• Verify smooth turning at finest setting
• Fill with peppercorns
• Give it a twist

A shower of pepper flakes in a cup:

The mill undergoes a full qualification test tomorrow morning, but those flakes look much better.

Fun fact: the OXO pepper mill holds 2.0 oz of peppercorns, so we use 0.033 oz = 940 mg of pepper every day.