4. Millstones

It seems the original Millstones fell and broke in the fire. I took this photo 12 years ago.

Luckily, along with the parts from the Mill which we have now discovered came from Cradock in the Eastern Cape nearly 800 km away, was a pair of matching stones, of a much lighter shade.

They are 'monolithic', that is one-piece, but the rough back of both has been filled up with Plaster-of-Paris or similar material. The balance-rynd was missing from the runner. I had one made and rather than setting it in with lead or Sulphur, I opted for Epidermix, a strong epoxy resin. The slot in the stone and the new rynd needed some fettling to fit centrally and level.

I masked it and poured the resin and left it to harden.

The balance-point can be seen in the picture above. If it doesn't balance on this, I'll have to add weights to the top. Where the resin didn't reach, I later tipped the stone up first on one side, then the other and poured more in, again allowing several days to harden.

The next problem was the Neck bearing. The one we found was a loose fit in the bed-stone and was badly worm-eaten and the hole was in bad condition. 

From Jon Stevens, who is doing the main carpentry on this job, I got an offcut of Ekki or Bilinga, slightly bigger than what was needed. It was irregularly shaped, so I used the belt-sander to flatten and square-up two adjacent sides, from which I could measure.

I started up the engine on the big woodworking machine and cut from both sides, the rough sides off, leaving a few millimetres to spare according to the size of the hole in the bed-stone.

The saw was set to do a 95mm cut which overlapped leaving a flat surface. The block was too wide for the normal 'fence' on the saw, so I had to put up a temporary one. I then made centre holes and tried it in my lathe, it was too big to turn.

I had to ask permission to use my old bigger lathe from the person who bought it from me.

I machined a cone on one end, which will face upwards. This will encourage grain falling from the shoe to move outwards into the 'swallow' at the beginning of the millstones. 

I was then ready to visit the farm again and fit it to the square hole in the Bed-stone. 

Using the belt-sander on the wooden block and a diamond-impregnated disc on the small grinder on the stone, I worked away, testing the fit frequently. 

Once I tried knocking it in and got about three-quarters in, then stuck, so I had to turn the stone over, knock it out and work out what was preventing it. Next time it went in with about 20mm to go, and I had to borrow the farm's sledgehammer to knock it in the last bit. It needs to be tight! 

I was worried that the top face of the Bed-stone wasn't flat.  It had to be relatively flat for the next operation, boring the hole for the stone-spindle. The hole has to be perpendicular to the top face and I'd prepared the boring bar I'd made for a job on Mostert's Mill, attached to an L-shaped pair of offcut Spruce beams. 

Using a heavy straight wooden square bar, I worked away on the high spots.

Then I could assemble the boring bar over the middle of the wooden block and check for squareness in two directions.

When I was happy, I reinforced the jig with extra blocks and clamps and started boring

The boring bar is 40mm and the hole was also 40, so it would have jammed, so I fitted the Forstner bit directly into the bar to start with to centralise, then withdrew and added an extension piece between. Then the hard work began! Drilling into end-grain of a piece of Bilinga or maybe Ekki is difficult and I soon realised other plans were needed! Next visit, I brought a blower to clear the fine sawdust, lubricant for the sticky boring bar and 'wood-slide' for the cutting tool itself. That helped, but again progress got slower and more difficult. I withdrew the cutting tool and sharpened it and every few millimetres I withdrew the tool completely, cleared sawdust from it and the hole, applied wood-slide and did some more. 

Eventually the cutting tool broke through after 225mm of drilling! I then counter-bored a little way with a 50mm Forstner bit, to be able to fit a lip-seal to hold back the grease I'm planning to apply under pressure from below.

In the following weeks I became worried that a stone spindle with a 40mm round section through the Neck bearing would lead to a squared-off-and-tapered top end too small to drive the Mace effectively, so on the next visit (luckily I hadn't dismantled the boring bar) I ran the 50mm Forstner bit right through. That sounds easy but it was hard work!

Naturally, in doing so, the 50mm recess for the seal was lost. The boring bar is drilled for a fly-cutter which was needed in its original application, boring the Tail-pole for Mostert's Mill for the Capstan. After checking for a popular seal size, I started cutting a counter-bore 10mm deep.

Gradually working outwards from then on in stages, I was aiming for 85mm in diameter. The bar is 40mm, so the cutting tool needed to protrude 22.5mm to make a radius of 42.5mm. The last half a millimetre was nail-biting!

The final result is much more satisfying!

Some months elapsed before we got further on this aspect. In the meantime we experienced a problem on the Neck-bearing at nearby La Motte, where the wood seized on to the Stone-spindle. This caused me to check on this one. Sure enough, the spindle wouldn't fit, and also, where I had forced the block into the Bed-stone, it was now loose. 

While I don't know much about the properties of wood, I do know those of metals, so I decided to remove it and bore it out further and fit a Phosphor-bronze bush. It came out easily and I brought it home. 

I would have had difficulty setting it up on the lathe I machined it on, to cut out a recess for a bush, so I used an offcut 50mm bright steel bar and drilled it across and inserted a fly-cutter. I made a video of the process which can be viewed on this link: https://www.youtube.com/watch?v=0lN6YEqQPOM&t=413s

I also machined and honed out a lot more of the original bore, to make sure there was clearance, and counterbored for another seal at the bottom. I then had a bush turned, with parallel knurling on the outside, and pressed it in:

On the next visit, I glued the block into the Bed-stone and left it to cure.

To be continued......