Frank Townend
01-14-2009, 10:10 AM
Background and Issues
A fellow turner provided some great insight into the mechanics of assembling the mill, which prompted me to exercise my engineering genes to see if I could design an easy to turn, bore, and assemble pepper mill which allows the greatest grain or lamination match, especially where there is a diagonal orientation of the lamination.
http://www.specialtyfoodamerica.com/CATALOG/CARNIVAL%202.jpg
Shown here are two mills where the parting and subsequent cutting back of a tenon for joining the two halves together show a discontinuity of pattern. (Note: I am not being critical of this turner's work, it is the nature of this type of turning and assembly.)
Here is a photo of the Crush Grind "Wood" pepper mill mechanism (http://www.allthingspepper.com/Tooling/mechanisms.php):
http://images.rockler.com/rockler/images/32708-03-80.jpg
As you can see it doesn't require a shaft, allows a mill of any size, and may be placed anywhere within the mill. The bottom is a hollow round cylinder with the grinder at the bottom, the top a smaller hollow cylinder with prongs at the top. It rotates where the top meets the bottom.
As my fellow turner and I discussed the assembly, he pointed out you glue the lower half of the mechanism to the lower part of your mill, and, using a brass rod inserted into a tenon, 'secure' the upper half of the mechanism to the upper part of your mill. By this we mean the prongs 'catch' the brass rod so that the top rotates as you turn the upper part of your mill.
Most instructions for use of these mechanisms require 'blind' boring a series of different size holes, of very specific length and even the cutting of a rebate in the top half to catch the ends of the prongs.
http://farm4.static.flickr.com/3319/3196126481_7bd3b12a1b_o.jpg
This picture shows the number of required hole sizes. The rebate or groove is designed to capture the prongs. You will also notice the tenon on the lower part of the blue top section of the mill. This is 'lost' to the outside of your mill, leading to discontinuity of grain or lamination. This design also requires creating a lid for the mill or unscrewing the grinder for refills.
My plan calls for the same size and number of holes, but allows them to be cut off of the lathe and allows of assembly in easy to accomplish steps.
Turning and Assembly
My suggestion was to use inserts or plugs (or sleeves) within each half of the mill, to aid assembly and allow for close tolerances between the two halves.
Here are the steps:
Turn a cylinder with one tenon at the headstock.
Mount the tenon into a chuck and turn to desired shape.
Finish the mill at this time if using a friction finish. (Other finishes may be applied later in the process if desired.)
Bore out one long wide hole, almost to the tenon, making a hollow cylinder. (If the bored hole has the same inside diameter of the cylinder as the outside diameter of the stock used for the inserts/plugs, so much the better.)
Either remove from lathe to 'part' using a band saw or thin-bladed chop saw; or part on lathe. (You now have a top half and a bottom half.) (The thinner the blade or part, the greater the match in grain or lamination.)
Sand and finish the two cut edges.
Create two plugs/inserts (O.D. = I.D. of cylinder) ; The bottom plug is as long as the mill mechanism lower half.) (The top plug/insert is as long as the mill mechanism upper half AND the distance the plug/insert will be inserted into the top half of the Mill.)
Drill one plug/insert for the bottom, sized for the bottom of the mill mechanism.
Drill one plug/insert for the top, sized for the top of the mill mechanism, drill for, and inset a thin brass rod through it to 'catch' the prongs of the top half of the mechanism .
Aligning the two plugs/inserts on the bench top; mark, drill, and insert two to four Neodymium magnets with opposing poles so, when aligned in the mill, the two halves of the mill will tightly fit together and stay together. (Don't use 'monster' magnets with 1,000 pound holding power, you want the mill to turn easily.)
Glue the top plug into the top half exposing .5" - 1" to be inserted into the bottom half.
Glue mechanism into bottom plug/insert. Install and glue the bottom plug/insert .5" - 1" down from the top of the bottom half. (If you wait for the glue of the top insert/plug to cure, you can insert the bottom plug/insert far enough to 'meet' the top insert/plug and ensure a nice tight fit.) (Also you can use thin plastic 'washers' on the matching surfaces to allow for a nice 'slick', smooth movement between the top and bottom.)
Assemble / Grind / Enjoy / Repeat.
http://farm4.static.flickr.com/3262/3195043660_d611eeda8f.jpg
While this drawing only shows one insert/plug/sleeve, you can easily make two which allow easier assembly.
Because someone, soon enough, will tell me to put my 'money where my mouth is', I will be trying out my plan this weekend and posting photographs of the progress/results.
A fellow turner provided some great insight into the mechanics of assembling the mill, which prompted me to exercise my engineering genes to see if I could design an easy to turn, bore, and assemble pepper mill which allows the greatest grain or lamination match, especially where there is a diagonal orientation of the lamination.
http://www.specialtyfoodamerica.com/CATALOG/CARNIVAL%202.jpg
Shown here are two mills where the parting and subsequent cutting back of a tenon for joining the two halves together show a discontinuity of pattern. (Note: I am not being critical of this turner's work, it is the nature of this type of turning and assembly.)
Here is a photo of the Crush Grind "Wood" pepper mill mechanism (http://www.allthingspepper.com/Tooling/mechanisms.php):
http://images.rockler.com/rockler/images/32708-03-80.jpg
As you can see it doesn't require a shaft, allows a mill of any size, and may be placed anywhere within the mill. The bottom is a hollow round cylinder with the grinder at the bottom, the top a smaller hollow cylinder with prongs at the top. It rotates where the top meets the bottom.
As my fellow turner and I discussed the assembly, he pointed out you glue the lower half of the mechanism to the lower part of your mill, and, using a brass rod inserted into a tenon, 'secure' the upper half of the mechanism to the upper part of your mill. By this we mean the prongs 'catch' the brass rod so that the top rotates as you turn the upper part of your mill.
Most instructions for use of these mechanisms require 'blind' boring a series of different size holes, of very specific length and even the cutting of a rebate in the top half to catch the ends of the prongs.
http://farm4.static.flickr.com/3319/3196126481_7bd3b12a1b_o.jpg
This picture shows the number of required hole sizes. The rebate or groove is designed to capture the prongs. You will also notice the tenon on the lower part of the blue top section of the mill. This is 'lost' to the outside of your mill, leading to discontinuity of grain or lamination. This design also requires creating a lid for the mill or unscrewing the grinder for refills.
My plan calls for the same size and number of holes, but allows them to be cut off of the lathe and allows of assembly in easy to accomplish steps.
Turning and Assembly
My suggestion was to use inserts or plugs (or sleeves) within each half of the mill, to aid assembly and allow for close tolerances between the two halves.
Here are the steps:
Turn a cylinder with one tenon at the headstock.
Mount the tenon into a chuck and turn to desired shape.
Finish the mill at this time if using a friction finish. (Other finishes may be applied later in the process if desired.)
Bore out one long wide hole, almost to the tenon, making a hollow cylinder. (If the bored hole has the same inside diameter of the cylinder as the outside diameter of the stock used for the inserts/plugs, so much the better.)
Either remove from lathe to 'part' using a band saw or thin-bladed chop saw; or part on lathe. (You now have a top half and a bottom half.) (The thinner the blade or part, the greater the match in grain or lamination.)
Sand and finish the two cut edges.
Create two plugs/inserts (O.D. = I.D. of cylinder) ; The bottom plug is as long as the mill mechanism lower half.) (The top plug/insert is as long as the mill mechanism upper half AND the distance the plug/insert will be inserted into the top half of the Mill.)
Drill one plug/insert for the bottom, sized for the bottom of the mill mechanism.
Drill one plug/insert for the top, sized for the top of the mill mechanism, drill for, and inset a thin brass rod through it to 'catch' the prongs of the top half of the mechanism .
Aligning the two plugs/inserts on the bench top; mark, drill, and insert two to four Neodymium magnets with opposing poles so, when aligned in the mill, the two halves of the mill will tightly fit together and stay together. (Don't use 'monster' magnets with 1,000 pound holding power, you want the mill to turn easily.)
Glue the top plug into the top half exposing .5" - 1" to be inserted into the bottom half.
Glue mechanism into bottom plug/insert. Install and glue the bottom plug/insert .5" - 1" down from the top of the bottom half. (If you wait for the glue of the top insert/plug to cure, you can insert the bottom plug/insert far enough to 'meet' the top insert/plug and ensure a nice tight fit.) (Also you can use thin plastic 'washers' on the matching surfaces to allow for a nice 'slick', smooth movement between the top and bottom.)
Assemble / Grind / Enjoy / Repeat.
http://farm4.static.flickr.com/3262/3195043660_d611eeda8f.jpg
While this drawing only shows one insert/plug/sleeve, you can easily make two which allow easier assembly.
Because someone, soon enough, will tell me to put my 'money where my mouth is', I will be trying out my plan this weekend and posting photographs of the progress/results.