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Installing A Peppermill Mechanism

Including how to shorten the driveshaft

Text & Photos by Tom Hintz

Note: This article describes how I install peppermill mechanisms. While most mechanisms are very similar, I may not have installed the brand you have. If the instructions accompanying your mechanism differ, follow them to insure proper operation.

   Peppermill mechanisms are very simple machines. A long driveshaft is secured to the head of the peppermill so when turned, it rotates the grinding cutter within the grinder housing at the bottom of the peppermill.
   While installing this hardware is simple, it is important to be sure it operates freely and that sufficient adjustment is available at the knob to allow the user to set it for a full range of particle sizes. This can involve shortening the driveshaft, a simple procedure we will cover later in this article. I buy my peppermill mechanisms longer than needed and then tailor the shaft to fit the peppermill rather than restrict turning the wood to a specific length to fit the driveshaft.

Check the Mechanism

Make sure all the parts are accounted for and fit together.
Click image to enlarge

   Lay out the peppermill mechanism to be sure all of the parts are present and that they fit together as designed. Though rare, finding a problem with the hardware now is much easier to deal with than after it has been installed. Be sure to screw the adjuster knob onto the shaft fully as the threads can be a little rough. Usually, if the knob feels tight when screwing it onto the driveshaft, running it on and off a few times cleans up the threads and smooths operation. Be sure to use a wire brush to clean shavings from the threads as you do this to prevent future problems.

Start at the Bottom

The grinder housing and spring/shaft retainer should be centered by eye before drilling the pilot holes.
Click image to enlarge

   Temporarily assemble the grinder housing and spring/shaft retainer making sure the retainer seats into the grooves in the outside of the grinder housing. Also, the grinder housing is oriented with the rounded inner edge facing downward.
   Hold this assembly in its recess in the bottom of the peppermill body. Center the assembly by eye and while holding it in this position, drill pilot holes for the screws that will secure it.

Install the Drive Plate

   Fit the driveshaft through the square hole in the drive plate and through the ¼"-diameter hole in the peppermill head and slide the drive plate against the tenon on the bottom of the head. Center the drive plate

The drive plate can be screwed to the face of the tenon or recessed as this one is.
Click image to enlarge

and shaft on the tenon and drill pilot holes for the screws that secure it. Install the screws and then check to be sure that the drive shaft passes through the drive plate and head without excessive resistance. Some instructions call for drilling a ¼"-diameter hole through the head for the driveshaft which can be a snug fit. Since the driveshaft does not turn within the head, as long as you can get it in and out, all is well. Remove the head from the driveshaft and set aside.

Assemble the Mechanism

   Slide the grinder core down the drive shaft, grinding teeth facing up. Place the grinder housing over the drive shaft, with the rounded end of the internal teeth facing downwards and fit it over the grinder core. Slip the spring over the drive shaft, with the narrow end against the grinder core. Note: The spring will work either way but the wide end fits over the flange on the underside of the spring/shaft retainer. Next comes the spring/shaft retainer. Slide it down the drive shaft, making sure its sides fit into the grooves in the grinder housing body.

(Top) Note the rounded edge of the grinder housing, indicating it's bottom end.
(Bottom) The grinder core fits into the housing almost flush when assembled correctly. Note how the bracket fits into the recesses on the sides of the housing.
Click images to enlarge

   Place this assembly into the peppermill body from the bottom. Center the screw tabs of the spring/drive shaft retainer over the holes drilled earlier. Place the mechanism retainer over the assembly with the stepped side facing down and the mounting tabs also centered over the screw holes. Install the retaining screws and snug them down. These screws need not be overly tight but rather just snug enough to fully seat the two sets of mounting tabs to the peppermill body.
   Slip the peppermill head over the threaded end of the drive shaft, turning it to match its square shaft to the square hole in the drive plate. Slide the head down, inserting the tenon into the body. Make sure the head is seated flush on the body.
   Screw the adjuster knob onto the drive shaft, turning it down until it is snug against the top of the peppermill head or until it bottoms out on the threads on the shaft. If the knob tightens against the peppermill head before bottoming on the threads, back it off about 1 turn. Your peppermill is complete.
   If the adjuster knob bottoms out on the threads before it contacts the peppermill head, proceed to the next step to shorten the driveshaft.

Shortening the Drive Shaft

   Reducing the length of the drive shaft to fit an already-made peppermill is simple and requires few tools to accomplish. All of the drive shafts I have seen are made from aluminum, a rather soft, malleable metal that we can form in our shops. A good vice with wooden jaws, hacksaw, metal file and a ball peen hammer are all you need.
   First, determine the amount of material to be removed from the drive shaft.
   With the adjusting knob screwed fully onto the threads, remove the mechanism retainer. Turn the peppermill upside down and stand it on the adjuster knob to push the excess driveshaft out through the bottom. Push the grinder core down against the spring pressure so it is fully seated in the grinder housing. Use a scratch awl (a sharp drywall screw works) to make a mark on the driveshaft even with the bottom surface of the grinder core. This marks where the cut will be made.

(Top) While holding the peppermill upside down, the adjusting knob pressed against the head and the grinder core fully in the hosing, mark the shaft flush with the bottom of the grinder core.
(Bottom) Cut off the extra material and peen the end over so it looks like the factory-prepared end cut off earlier.
Click images to enlarge
   Cutting the excess driveshaft material away on this mark insures producing a perfect-length shaft. Making the cut flush with the bottom of the grinder core and then mushrooming the end effectively shortens the driveshaft approximately 1/8". That sinks the threaded end into the head just enough to insure being able to snug the adjuster knob down against the wood but having plenty of adjustment available.
   Remove the adjuster knob from the drive shaft and then the grinding mechanism from the peppermill body. Slide the parts off the driveshaft and set aside.
   Clamp the driveshaft in the vise and cut the excess material off at the mark.
   Clamp the remaining driveshaft into the vise, the cut end up, with the end about ½" above the wooden jaws of the vise. Clamp the driveshaft tightly so it can resist moderate pounding action to come next.
   Using the rounded face of the ball peen hammer pound the cut end of the driveshaft, expanding the metal into a mushroom shape. The blows need not be hard but rather just forceful enough to begin distorting the metal. Continue shaping the new end until it appears similar to the factory-prepared end cut off earlier.
   When satisfied with the newly formed driveshaft end, turn the hammer around and give the driveshaft a few blows with the flat face to smooth the surface a bit.
   Remove the drive shaft from the vise and slip the grinder core down to the end to check the fit. Usually there is a square recess in the bottom of the grinder core into which the mushroomed end of the driveshaft fits. It may be necessary to file the outer edges of the mushroomed end slightly to fit this recess.
   If desired, the hammered end of the driveshaft can be lightly sanded to smooth its surface further, though this is not necessary.
   Make sure all metal filings have been cleaned from the mechanism parts and peppermill before continuing!
Salt Shaker and Peppermill Hardware
Salt Shaker and Peppermill Hardware

   Reassemble the peppermill mechanism into the body as described earlier. Install the peppermill head, screw the adjuster nut onto the driveshaft and snug it down. It should contact the head of the peppermill slightly before it bottoms out on the threads. This allows a full range of adjustment of the mechanism while maintaining plenty of threads in the adjuster knob to secure the peppermill head.
   That's it. Your peppermill is ready for use.

Also see Turning A Peppermill

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