Likely a "diary to self" note...
Yesterday in conversation with a friend the significance of the sieve analysis just done came back to me. A process of collecting thoughts after the details of that endeavour lost the "big picture".
Venturing into comminution, "rod-mill" was an achievable goal and the reputed characteristics seemed useful if obtained. While in all circumstances being a good focus to seek observation of outcomes.
Quantifying and analysing the rod-milling outcome then came into view...
My continuing impression is I need to "calibrate" my rod-mill.
Inspiration is eg in Wills' book with
Gates-Gaudin-Schulmann plots (8th Edn. - Fig 4.7) of
particle-size evolving in grinding time.
At time of writing (Sunday 13 July 2025 at 06:43) this remains ahead of me (eg this sieve-analysis is on a learning-curve (in both the comminution and the particle-size-analysis)).
This line-of-thought I explained is at the core of the current endeavour:
reference feed
v
mill
v
particle size analysis / sieve analysis
Real ore samples are "precious". Much effort has usually gone into
scavenging them from marginal sources.
Also they are inhomogenous between "batches": sizes as-supplied;
hardness / strength / toughness; an ore is inherently mixed materials
anyway; etc. Which is going to defeat rapidly building up a
correlations-map in your mind and in data, while giving sub-optimal
result to those who collected precious ore samples.
To "calibrate" the rod-mill a "reference feed" seems desirable
For my rod-mill I identified 10mm granite grey chippings for surfacing
pathways.
This can be bought in sacks from builders merchants.
In one area the granite chippings seem likely to come from one quarry,
and even if not, customer appeal as pathway surfacing material would
tend to uniformity of colour, texture, etc.
Grinding this "low-value, no-purpose" feed should enable me to build an image in mind - and data; hence sieve-analysis and particle-size-analysis - of the effects of grinding time; mill rotational speed; changing the configuration of the mill; etc.
Further ahead, I could seek a "more readily grind-able reference feed
material", so can then build more dimensions to the picture of
comminution performance.
Variables might be : not use the largest rods available for the rod
mill and increase the number of "medium" and smaller rods; lower the
mill rotation speed so "cascading" not "cateracting"; shorter grinding
times; etc.
Thinking ahead to most ores being softer / more friable than granite
chippings...
Also that ores are inherently multi-component - typically mineral and
gangue; either or both of which may be mixed types.
The objective is to be able to make a very good guided guess how to
process a finite batch of a "precious" ore collected by the local
mineral and mining enthusiasts community.
How to "get very close to the bullseye" with no opportunity to
practice the milling.
Quite quickly got "functions" to calculate rotating tumbling mill characteristics like
These enabled me to design the "metallurgical" part of the mill. Which then gave the requirements which specified the "mechanical" part of the mill.
In the run of things - stops those comments where, seeing a running rod-mill, it is suggested that I could calculate the critical speed for the mill... :-)
Needs a hermetically sealing cover for the end of the mill (my rod-mill is a batching mill - load it; put cover on shell; run mill for a time; retrieve comminute from within mill).
Hermetically sealed so the rod-mill can be run
This is some metalworking. Given my Trade as a welder-fabricator - need to head-off to shed and do what needs to be done.
Mentoring, guidance and assistance gave me a mill which works.
That is usually "unmissable" - get something outputting as soon
as possible.
Totally excellent is that I was shown the way of getting a freely variable speed drive to the mill. That was a supreme bonus.
However, the current "get something working" mechanical arrangement has limitations
Hoped-for ores:
(R. Smith, 13Jul2025, 14Jul2025 (eds.))