Mill Stones




As most of you can tell by now I love old mill buildings and grist mills are right up there on my list.   I had been wanting to make up a set of mill stone patterns so I could make castings and sell them.  So, I had to do some research.  Since grist mills were nearly in every early American town and many survived well into the 20th Century I figure it would be a good idea to post some of the things I’ve found out about them over the years.  What’s the use of modeling an item if you don’t know anything about it, right?

So, what is grist?

Grist:  a :  grain or a batch of grain for grinding b :  the product obtained from a grist of grain including the flour or meal and the grain offals

Simply put crushed and ground grain.

 

How do you grind grain?

In a stone mill.  Well, stone was used since it was a durable and fairly available commodity around farms at that time, but hard cast iron “stones” are now common in industrial mills. However, there has been a resurgence in stone ground grain for those who like to bake their own bread and some small mills still use actual stones.  Even though redressing mill stones is a lost art, there are those who still do it out of necessity and do it mostly on a volunteer level.  I don’t know if there are traveling stone dressers, nor do I know if it would be a lucrative business.  I myself would rig up some sort of mechanism to take the drudgery out of it because  I couldn’t see myself bent over for hours chipping away at a stone wheel like that.  I’d never be able to get up.

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1. Hopper, 2. Shoe, 3. Crook string, 4. Shoe handle, 5. Damsel, 6. Eye, 7. Runner stone, 8. Bed stone, 9. Rind, 10. Mace, 11. Stone spindle, 12. Mill stone support, 13. Wooden timbers, 14. Casing Note: Tindering is not shown

 

mill
The mill. The two hand wheels down at the bottom and to the left are for dis-engaging from the drive gears and for adjusting the distance between the top and bottom stones.

 

Here’s a link to a mill where they are dressing  a stone.

 

 

 

Some Stone Terminology:

millstone_anatomy
I may be wrong, but it sure does seem like the “direction of spin” would cause the grain to flow inward. I would think that if it spun the other way the grain would flow outward toward the skirt. Any experts want to chime in?

 

dressing
Various dressings. These wheels are from different mills from around New England. Each miller had his own thoughts on the best dressing pattern and usually stuck with that particular pattern for the rest of their lives, so it’s highly unlikely that you would see two different designs at the same mill. These pics were taken at the Wayside Inn grist mill museum, which was built by Henry Ford as a tribute to early water power and industry.

 


 

Modeling mill stones.  (Or, milling mill stones)

So, now that I knew the whats and whys of stone dressing I decided to make some for sale.  Although there are a few different furrow patterns, I opted for what I consider the standard pattern as seen above.   I’ll probably make some spiral dressed wheels, one of these days.   They are pretty cool looking.    I drew this up in my trusty 10yr old copy of AutoCAD then loaded it up into my Cut2d program that is specifically designed to generate code for my CNC router.  My first tries didn’t work due to my own fault, but I figured that and used it as a test to get all the depths and tooling right.  I found that I could use a .020″ endmill (carbide burr) for most of the O-scale stones, but still had to use a modified engraving bit for the smaller HO scale stones.

Sorry, but I didn’t take any pictures of the router operations.

bits
The bit on the left is a commercially available .02 tapered roughing bur. The one of the right is one of my modified burs. I use a diamond bur to grind down the carbide bur. The shafts of the burs are 2.35mm (.090″) dia. if that gives you any idea of how small these bits happen to be. The bit on the right is about as fragile as bits come and are only used for pattern making. I would never use these for production purposes.  I still haven’t found an off the shelf bit that works as well as my handcrafted ones that doesn’t cost an arm and a leg. Seriously, if I had to buy the same bits I make and had to replace them as much as I do, I’d given up a long time ago.

 

o-scale_mill_stone2
Yes, they are green. It’s a special “die stone” used in the dental prosthetics field. It’s hard and has minimal shrinkage and is perfect for making master patterns. These two are actually castings made the molds from my original milled patterns. They still need more work. Most top mill stones had holes drilled on the sides for a set of tongs, or bails for lifting the stones for dressing.  See video above.

 

bail_holes
Bail or lifting holes.

 

 

 

finished
These were pulled from the first molds and colored with thinned acrylic paints applied with a kitchen sponge just to get an idea of how they would look.  These are small for O-scale.  Most stones are 4-5 feet in diameter.

 

Mill Stone Jewelry

What?  Yeah, I know, but when you have a handful of mill stone castings and another handful of jewelry components the natural thing to do is to combine.  Actually, I needed a Secret Santa gift and decided to make mine this year instead of giving a gift card or finding something for $20.  I hate shopping, unless it’s for tools, so I went to work.  Honestly, by the time I finished this set of necklace and earrings value out at more than $20, so someone got the better deal. 🙂

Of course, I had to make a set for my wife Tina.

millstonejewelry
The stones at the bottom are the original plaster millstone castings. The jewelry stones are cast in resin with a stone filler that works fairly well for this project. The filler is made for casting larger fake stones and has larger chunks of (fake?) mica that had to be screened out.
msmodeled
The loop is glued into a slot that works well and is easy enough to mount in place, but a cast bail like the one shown below would make a much better mount for the stone and increase it’s potential conversation value.\
Original loop setting for chain , on left. New awesome bail setting is on the right. Now to get it cast.

 

lifting_bails
Set of lifting bails and crane for removing the top stone for dressing. Brian Bollinger of BEST Trains is inspecting the screw. It’s made of wood, BTW.

 


More mill pictures.

 

Even though this page is mainly about mill stones, it would be useless if I didn’t have some pictures of how it all goes together.   Unless you are building a detail interior, most people would be happy to have a couple of stones laying around a model and call it quits, which is fine, but not knowing how it works is doing Henry Ford and all of those millers a big dis-service.  As usual, you’re gonna get more info from me than really needed.  Here are some pictures of the inside of the mill building.  If you do want to build a mill with a detailed interior I do have many more pictures of this particular mill and I will put them into a gallery for your enjoyment and use.

If you would like to visit the Sudbury Mill.  The Sudbury Mill and Pepperidge Farms

headrace
Head race from the dam.

 

headrace2
Head race at the mill.

 

spillway_top
Head race, spillway and forebay. The forebay is the area just in front of the gates. Forebays act as small reservoirs or equalizers that maintain enough water to keep the gates full. Think of it as the opposite of a bottleneck. The rusty piece of channel iron to the right of the spillway is for blocking off the forebay for maintenance purposes. Boards would be slid down into the channels thus creating a temporary dam that would keep the water out of the work area.  I’m surprised there isn’t a trash-rack mounted here.

 

gate_control_wheel
Gate control wheel. There doesn’t seem to be any governor set up, so the miller would have to look at the speed indicator and adjust the flow manually.
speed_dial
Speed indicator

 

gate2
Gate from the wheel side. The gate was operated from inside by a hand wheel that was connected to the shaft going through the wall and out along he top of the gate stone work. There are two small pinion gears on the shaft that engage a couple of rack gears mounted to the gate stems (the two vertical red pieces) The three steel bars hold up the trough that guides the water onto the wheel.

 

 

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Steel wheel and bearing.  Most of the time we think of gristmills with wooden wheels, but steel wheels were available around the latter part of the 1800’s.   Even so, most mill owners with any fore thought would have converted to turbine power when the old wheel had served it’s life.

 

damsel
The curly cue looking piece is called the shoe handle. It is connected to the shoe which sits below the hopper above. There is a hexagon shaped rod called the damsel that is attached to the main drive shaft coming up from the basement that the shoe handle rubs up against. It works like a cam that causes the shoe to move out then swing back into the damsel causing it to vibrate the shoe and feed grain into the wheel at a steady pace.

 

power_train
Drive train. Since water wheels turn at slow speeds and mills turn faster it is necessary to speed up or up-gear the drive train. The big wheel in the back against the wall is connected directly to the water wheel outside and turns the smaller pinion to the right of it. It looks to be a 6:1 ratio. So, if the big wheel makes 1 turn, the smaller pinion gear will turn 6 times faster. Since it is connected to the big wheel in the foreground, that wheel will be turning 6 times faster than the water wheel outside.

 

power_train4
Maintenance. The top beveled gear is being held up by a modern come-along and chains, evidently for maintenance or repairs. The long bar extending from the central shaft is forked shaped and engages the thrust bearing which allows the miller to turn the mill stone off and on.

 

power_train3
Same mill, different view. The bar on top of the top gear is for adjusting the distance between the stones.

 

power_train2
How the gearing usually looks during normal operation. The teeth on the gear on the horizontal shaft are made of wood. This was done not only as a safety precaution in-case the mill jammed or locked up, but also because it was cheaper to let the teeth take the wear on one gear than to have to replace two iron gears.

Some pictures of the building’s stone work.

 

gristmill2

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wheel

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