From Newsgroup: rec.crafts.metalworking

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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From Newsgroup: rec.crafts.metalworking

"Richard Smith" wrote in message news:m1free83oi.fsf@void.com...

...Got someone keen to do this who has lathe, etc...

Good. You will see how greatly it expands what else you could consider
trying. A lathe and milling machine sized to your intended projects really open doors to creativity. They enabled the Industrial Revolution, the steam engine had already been in use for ~100 years without making much difference because it remained primitive and inefficient without them.

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From Newsgroup: rec.crafts.metalworking

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-a copper.

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From Newsgroup: rec.crafts.metalworking

"Richard Smith" wrote in message news:m1free83oi.fsf@void.com...

I've arrived at a new mechanical-part design for the rod-mill where
drive is through the wheels the shell rotates on.

I have an old Thumler like this whose (only) advantage is simple
construction.
https://rocktumbler.com/thumlers/model-ar-2.shtml

The drive has more authority to lift the balls/rods/pebbles with both roller shafts belted together, and friction tape etc on the drum. The plastic shaft bearings are a type used on garden equipment, the rollers can be soft rubber tubing or if larger to clear the end cap have tread cut from a bicycle inner tube. The drum needs some restraint from shifting too far endwise. Perhaps
the end caps could be rubber caps for plastic drain & culvert pipe which
would also aid traction and might dampen noise. You could bolt clear plastic over central holes in them to observe and adjust the action of the rods.

Since the ribs need to lift the rods more than the charge, they could be replaced by pairs of screws from outside, preferably in tapped holes. Nuts
and washers on the inner end could raise the rods higher before they roll
off. If screws don't work by themselves they could attach metal rib strips such as sheet metal angles trimmed and bent for best performance. This would make stirring the charge and dropping the rods easily and independently adjustable.

Screw hole locations could be marked on paper whose length equals the drum circumference. Aligning the ends of the paper positions the holes for center punching as accurately as the paper layout. You could start with one pair
and observe where a rod lands when dropped from as high as practical, to
space the others away from the landing area.

This gives the general idea of how to divide the length of the circumference into equal parts by angling the ruler. https://www.woodmagazine.com/woodworking-how-to/shop-tips/layout-measuring-marking/get-equal-spacing-in-seconds-with-no-math

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From Newsgroup: rec.crafts.metalworking

"David Billington" wrote in message news:106cupp$3598s$1@dont-email.me...

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.

I salvaged some scrapped 95-5 Sn+Sb solder from the trash at work when they rebuilt a set of heatsinks for temperature cycling GM ignition modules. It
can be cast into work holding fixtures in wooden molds without charring them as lead casting does, so I made a vee block that can be drilled into. When bent it makes the "tin cry".
https://en.wikipedia.org/wiki/Tin_cry

https://en.wikipedia.org/wiki/Plaster_mold_casting

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From Newsgroup: rec.crafts.metalworking

"Jim Wilkins" wrote in message news:106d7pt$381ra$1@dont-email.me...

Screw hole locations could be marked on paper whose length equals the drum circumference. Aligning the ends of the paper positions the holes for
center punching as accurately as the paper layout.

As I lack the experience to guess what will eventually work best I've describes a way to make the rod tumbler innards easy to modify. I've assumed that the rods will be most effective if dropped as far as possible, more
stamp than ball mill. The reason for initially tapping the holes is limited wrench access inside the cylinder, they can be drilled out later.

When I plan to drill multiple copies of a hole pattern and can't mount the work on the mill I make a guide plate to clamp on and drill through. For drilling the tumbler cylinder the guide could be a bar longer enough to be supported at the ends with the cylinder clamped on and hanging underneath. This would let the job be done on a drill press with minimal fixturing, only the end support blocks. The guide can also locate the matching mounting
holes in the internal ribs. The guide will stay accurate longer if used with
a center or transfer punch than drilled through, which opens the holes in
mild steel. Purchased drill guide bushings are hardened. https://www.amazon.com/06111TK-3pck-Drill-Guide-Bushings/dp/B005GFL5IU

A tap hole sized drill gauge works for both tapped and clearance holes,
which are drilled larger afterwards. My more permanent drill guides have tapped holes for cylindrical guide sleeves turned on the lathe, which can be duplicated when worn. Mine are longer than commercial guide bushings for freehand use such as drilling out a broken stud in a car engine. Transfer punches let me accurately copy the center pattern of the oversized holes on the ignition module to make the drill guide mounting plate that fit snugly
on the remaining studs.

https://www.harborfreight.com/28-piece-transfer-punch-set-3577.html?

Before owning machine tools I had to learn these manual methods and
equipment for reasonably accurate metalworking. I still use them on
components too large to put on the mill, like the gantry track beams.

https://www.practicalmachinist.com/forum/threads/finding-the-center-of-a-cylinder-for-cross-drilling.80238/
"Pinch a piece of flat stock between the cylinder and a [drill bit] center point in the spindle. When the flat stock is parallel to the cylinder's mounting surface [drill press table] the point is at the tangent."

jsw

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From Newsgroup: rec.crafts.metalworking

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-a 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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From Newsgroup: rec.crafts.metalworking

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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From Newsgroup: rec.crafts.metalworking

"Richard Smith" wrote in message news:m1cy9fqwwf.fsf@void.com...

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.

-------------------------------------------------
There are many tricks and short cuts to be learned during the apprentice phase. Until fairly recently they were passed on verbally, the way I learned accurate manual woodworking and some blacksmithing. I have collected
reprints of the few books that recorded them for formal group instruction.
An engineer at Segway had a good library of the originals, but no home
machine shop until I directed him to one that was for sale and helped him
move it.

The "best fit" orientation can be permanently marked with a center punch or chisel. Nail polish holds up well and has a brush to apply it. An
inexpensive set of letter and number punches helps for more complex assemblies.

Shopping for nail polish in the bright primary colors provokes an
interesting reaction from sales girls until I explain that colors code for numbers in electronics. I'd drop a "Kinky Boots" reference if those around here were more familiar with West End musicals.

When I use those 2300 year old geometric layout methods I put sticky labels
on the areas of interest so I can make and correct the trial marks in
pencil. Scribing on the metal with a sharp point after getting close enough
on paper by trial and error is more accurate but not erasable. I first use a shop-made acutely angled "prick" punch that can track along a scribed line
to an intersection by feel, then follow with the drill point shaped center punch. On a good day that's accurate to ~0.1mm.

Drilling and tapping by hand is squarer if you have a reference such as a
vee block to square the tool to the work. I carried a small cabinet hinge in my pocket to use as the vee block guide. I haven't seen that idea of mine in print.

Tapping is easier and less risky with industrial cutting fluid or pipe threading oil. Kerosine works on aluminum. A tap can be sharpened by stoning the grooves. Round rods and fish hook stones may fit better.

The vee head on a combination square locates diameters. https://www.harborfreight.com/12-in-combination-square-set-63688.html?

If you lay a framing square on a circle with its corner touching the circumference, the legs will intersect the circumference at diametrically opposite points. This is the secret of the core box plane. https://www.woodmagazine.com/woodworking-tools/hand/the-stanley-57-core-box-plane

Similarly a half hexagon recess can be milled with a straight end mill, to make a custom 6 point box wrench in two bolt-together halves. I made one to reshape and loosen distorted brake line fittings.

A center in an open hole such as on a rough casting can be located and
punched by fitting a wooden plug into it and then tapping on a square of
sheet metal with the corners folded to stick in.

Holtzapffel wrote that prior to Ramsden's dividing engine gear tooth angles were laid out by repeatedly stepping dividers around the circle and
correcting the closing error until good enough. His works are excellent descriptions of the struggles of pre-industrial "accurate" manual
metalworking and how they were gradually solved. Volume 2 has hand tools. https://archive.org/details/pli.kerala.rare.6416
I have an antique die stock like item 569 on page 598. It squeezes as much
as cuts the threads, which is appropriate for wrought iron with lengthwise grain that could break if cut.

Lindsay reprinted several tool-making instruction manuals from the late
1800's and early 1900's that include the old manual methods plus newer ones applicable to moderately equipped hobbyists. https://ia601309.us.archive.org/8/items/accuratetoolwor00stangoog/accuratetoolwor00stangoog.pdf
I don't have enough data ration left this month (7/7-8/6) to check for more.

Don't try the suggestion to straighten a bent shaft with a hammer while it's held between lathe centers, otherwise they still apply.

I've never found a piece of pipe or tubing rolled and welded from flat stock to be accurately round, especially around the weld. I use machined brass
pipe fittings to center other threaded fittings in a lathe chuck. Electrical conduit may be better because the inner weld bead has been drawn smooth.
jsw

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From Newsgroup: rec.crafts.metalworking

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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From Newsgroup: rec.crafts.metalworking

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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