Hello all

A "For what it's worth" thread for these mineral processing
endeavours. From here in Cornwall, UK.

Often have metalworking issues here. Made the rod-mill (and other
equipment) mentioned here - previous discussions.

Latest sieve-analysis of updated rod-mill webpage.
Has graph of the output mass-at-size distribution.

http://weldsmith.co.uk/tech/minerals/250723_sa_rm10gran/250723_sa_rm10gran.html "Particle Size Analysis rod-mill comminute 10mm granite chippings 23July2025"

Surely that's way too many fines?
I'm suspecting it's those completely misunderstood "lifters".
Apparently bead-on-plate weld runs are tall enough for this 220mm
internal diameter mill shell.
Their only purpose is to stop the entire charge of mineral and
grinding media - balls or rods - skidding at the bottom of the mill
with no tumbling action. If they drag the rock / ore / mineral
material along at the lowest position, it's enough to force tumbling.


Comment, for what it's worth...

I got 83% of those 1016g of fines out by sedimentation in water. Stir
the comminute and water in a bucket with a plaster-mixer, bring to a
stop by reversing the drill, leave 10 seconds, then ladle from within
50mm of the surface through the 75micron sieve into another bucket.
Stokes' Law with water medium - in 10s anything bigger than 75micron
has descended more than 50mm :-)
The opaque fluid pours straight through the 75micron sieve - nothing
on top.
When, prior to calculations, I left it 6 seconds, I got some particles
on the sieve. Surface tension of water is like glue at those sizes
and it's work getting the above-sieve off.
You could have knocked me over with a feather when I found this
worked. I "synthesised" the idea.

The advantages are - removing the very-fines first

* if dry-sieve, enough of the recently broken silica is gone that,
work outdoors and do stand upwind, but can have no detectable fines
produced

* wet-sieve or dry-sieve, especially wet-sieve, "all" you have is
granular particles, none of the clay-ey silt-ey material which makes
things "clog"

The 17% mass of the sub-75microns separated during the later sieving
was visibly just sub 75 microns. Sparkly grains, not fine clay / silt
like you see in the tidal flats of an estuary.


I've arrived at a new mechanical-part design for the rod-mill where
drive is through the wheels the shell rotates on.
Got someone keen to do this who has lathe, etc.
Then can cut out the far end plate where the current drive comes in,
remove the current "lifters", have new lifters of about 5mm height,
and see what I get then - do more sieve-analysis.


Got folk making it known they have cassiterite (tin ore) they want to
mill. Aiming for separation and smelt.
Also could do some chalcopyrite (the "primary" "volcanic sulphide"
copper ore).
Already done galena (lead ore) - good separation and smelted out a
small ingot of lead using cupellation.

Regards,

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On 30/07/2025 09:48, Richard Smith wrote:

Hello all

A "For what it's worth" thread for these mineral processing
endeavours. From here in Cornwall, UK.

Often have metalworking issues here. Made the rod-mill (and other
equipment) mentioned here - previous discussions.

Latest sieve-analysis of updated rod-mill webpage.
Has graph of the output mass-at-size distribution.

http://weldsmith.co.uk/tech/minerals/250723_sa_rm10gran/250723_sa_rm10gran.html
"Particle Size Analysis rod-mill comminute 10mm granite chippings 23July2025"

Surely that's way too many fines?
I'm suspecting it's those completely misunderstood "lifters".
Apparently bead-on-plate weld runs are tall enough for this 220mm
internal diameter mill shell.
Their only purpose is to stop the entire charge of mineral and
grinding media - balls or rods - skidding at the bottom of the mill
with no tumbling action. If they drag the rock / ore / mineral
material along at the lowest position, it's enough to force tumbling.

Comment, for what it's worth...

I got 83% of those 1016g of fines out by sedimentation in water. Stir
the comminute and water in a bucket with a plaster-mixer, bring to a
stop by reversing the drill, leave 10 seconds, then ladle from within
50mm of the surface through the 75micron sieve into another bucket.
Stokes' Law with water medium - in 10s anything bigger than 75micron
has descended more than 50mm :-)
The opaque fluid pours straight through the 75micron sieve - nothing
on top.
When, prior to calculations, I left it 6 seconds, I got some particles
on the sieve. Surface tension of water is like glue at those sizes
and it's work getting the above-sieve off.
You could have knocked me over with a feather when I found this
worked. I "synthesised" the idea.

The advantages are - removing the very-fines first

* if dry-sieve, enough of the recently broken silica is gone that,
work outdoors and do stand upwind, but can have no detectable fines
produced

* wet-sieve or dry-sieve, especially wet-sieve, "all" you have is
granular particles, none of the clay-ey silt-ey material which makes
things "clog"

The 17% mass of the sub-75microns separated during the later sieving
was visibly just sub 75 microns. Sparkly grains, not fine clay / silt
like you see in the tidal flats of an estuary.

I've arrived at a new mechanical-part design for the rod-mill where
drive is through the wheels the shell rotates on.
Got someone keen to do this who has lathe, etc.
Then can cut out the far end plate where the current drive comes in,
remove the current "lifters", have new lifters of about 5mm height,
and see what I get then - do more sieve-analysis.

Got folk making it known they have cassiterite (tin ore) they want to
mill. Aiming for separation and smelt.
Also could do some chalcopyrite (the "primary" "volcanic sulphide"
copper ore).
Already done galena (lead ore) - good separation and smelted out a
small ingot of lead using cupellation.

Regards,

All good work. Does anyone have any ore for antimony, then with the
copper and tin you can make some Britannia metal (modern pewter), for
sheet it's normally 92-6-2 tin antimony  copper.

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David Billington <djb@invalid.com> writes:

On 30/07/2025 09:48, Richard Smith wrote:

Hello all
...
Regards,

All good work. Does anyone have any ore for antimony, then with the
copper and tin you can make some Britannia metal (modern pewter), for
sheet it's normally 92-6-2 tin antimony  copper.

Never thought of that.
Not heard of antimony in Cornwall.
Can't say as I will work all night on that, but interesting thought.

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I have a long long way to go along this path!

I got "accurate enough" arrangement with dividers.
Was it you mentioned trammel points, which would have been better.

Methods best seen online...

Finding circular plate centre - scribed chords with rule-and-scriber
then divider from each end of chord method.

All the rest I did with dividers. Sole method.

Worked well.


Then from that centre identified, with dividers mark the PCD (pitch-circle-diameter), centre-pop one starting position on it and use dividers again on PCD radius to mark off the six positions
(you'll be knowing the special "law of the universe" property of a compass/dividers to create a hexagon).
From the disk centre I also marked-out the as-best-measured diameter of
the tube, and fiddled the position of the circular plate on the tube end
to give the best averaged fit before marking-out the six "things" (block
with a clearance hole for the thread) circumferential positions.

There is one "best fit", and its 180deg rotation is almost as good.
Other 4 of the 6 positions - could force it, but don't.
Thing is, got the job done, and the tube isn't machine-precision-round
anyway.

Experience I had - do use the specific tapping-size drill. The tap
"picks-up" and wants to run true to the drilled holes.

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I found the one about a very sharp narrow angle punch to "feel" a
scribed line and its intersection with another.

Amazing tools you describe!

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The "prick punch"...
I found it very prone to snapping off its tip.
Seems to me - tap it lightly with a hammer to leave a small prick mark,
then feel a sharp centre-punch with a reasonable angle into that mark
and belt it.

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