You have proved to be a remarkable font of knowledge.

Fancifully looking forward to tunnel-blasting rock (local is a very
hard granite) I looked to the "stemming". What you put put in the
collar of the drilled hole beyond the last charged blasting medium, to
effect a seal intensifying the blasting effect.

I know the one about if you try to press ceramic material down a hole
(or die or mould) it "bridges" and "locks". So I see "stemming" would
work in that way and is a good idea.
Then with a gravel stemming all that happens when it does "let go" is
a spray of grit - no heavy projectiles.

So that seemed a motivation to make a small jaw-crusher (best type of
crusher?) which can convert lumps of the granite into sharp gravel
about 4mm to 5mm size (?) to pack down the hole filling to the last
charge.

Whatever - it's a project.
I hear that a double-toggle crusher is best for very hard stone -
which this granite is. Giving a pure crushing action.
A single-toggle crusher with the eccentric shaft above the inlet for
the rock produces a combined crushing+shear as the moving jaw also has
up-and-down movement - which is reputed to increase throughput for
softer rocks but produce extra wear for no advantage on hard rocks.

Or does this not matter at small sizes?

I was thinking about 5"/125mm to 6"/150mm inlet capacity.
So quite a small machine.
Big rocks could be split with "feathers" - drill a socket, put in the
"feathers" and the wedge and split the rock.
We are not talking of huge quantities here.

Fanciful for sure. No-one at the mo. has a current blasting licence,
for a start...

But anyway - any experience?
I was thinking welded steel construction.
Apart from the jaws.
Cast very hard metal?
Cast "Hadfield Manganese Steel"?
Structural steel plate with welded hard-facing?

Regards,
Rich Smith

"Richard Smith" wrote in message news:m14jecdcjc.fsf@void.com...

You have proved to be a remarkable font of knowledge.

Fancifully looking forward to tunnel-blasting rock (local is a very
hard granite) I looked to the "stemming". What you put put in the
collar of the drilled hole beyond the last charged blasting medium, to
effect a seal intensifying the blasting effect.

I know the one about if you try to press ceramic material down a hole
(or die or mould) it "bridges" and "locks". So I see "stemming" would
work in that way and is a good idea.
Then with a gravel stemming all that happens when it does "let go" is
a spray of grit - no heavy projectiles.

So that seemed a motivation to make a small jaw-crusher (best type of
crusher?) which can convert lumps of the granite into sharp gravel
about 4mm to 5mm size (?) to pack down the hole filling to the last
charge.

[What protects the wires to the blasting cap?]

Big rocks could be split with "feathers" - drill a socket, put in the
"feathers" and the wedge and split the rock.
We are not talking of huge quantities here.

[Wedges and shims or "feathers" is what I use to cut away granite protruding
into the paths around my house, which was crammed into a rocky hillside.

I've watched large granite boulders at a blasting site being broken up for
fill with a hydraulic "pecker" which is an oscillating single point chisel
mounted on a tracked excavator in place of the bucket. They said the
vibrations damaged the excavator so they used an old worn one for this job.
A single point carbide-tipped chisel is recommended for manually carving
granite too.

Apparently "Excavator" is also the British term. In German it's "Bagger".]
https://www.youtube.com/watch?v=VBMUvAUPTGM

Fanciful for sure. No-one at the mo. has a current blasting licence,
for a start...

But anyway - any experience?
I was thinking welded steel construction.
Apart from the jaws.
Cast very hard metal?
Cast "Hadfield Manganese Steel"?
Structural steel plate with welded hard-facing?

[Around here AR400 is commonly used for repairs and mods to construction
equipment.]
https://www.steelwarehouse.com/ar400/

Current practice seems to be to use "Nonel" (non-electric) detonators.
Brilliant explanation at
YouTube channel
https://www.youtube.com/@mbmmllc

Video of "Opening My Gold Mine" series
"Opening My Gold Mine! Part 12: Last Drill & Blast"
go to about 23:39 / 36:20

* there's two delays - 0.3s at the clamp to pass on to the next shock tube
and 7s at the actual "blasting cap"

* the detonator goes to the bottom of the hole, so the blast propagation
is from deepest to near surface

* the "Nonel" tube conducting the shock/signal holds intact and does not
disturb the stemming or the blasting material it runs past

* the use of the delays is well explained in the video

Hope this is helpful

The "AR400" I think that is for excavator bucket lining and the like -
nothing like as hard as a rock crusher working face needs to be?

"Richard Smith" wrote in message news:m14jecdcjc.fsf@void.com...

But anyway - any experience?
I was thinking welded steel construction.
Apart from the jaws.
Cast very hard metal?
Cast "Hadfield Manganese Steel"?
Structural steel plate with welded hard-facing?

--------------------
I bought proper material when building for paying customers, otherwise after
roughly estimating the demands I searched out what was available locally and
designed around it, usually in my head when I found it. This avoids minimum
ordering quantities and long waits. It helps a lot to pay attention to what
others have used to solve similar problems, and to own or have access to
machine shop equipment to modify stock shapes.

I depend on a medium sized vertical knee-type milling machine, a
thread-cutting lathe similar to a Myford, a 4"x6" horizontal metal-cutting
bandsaw and a pedestal grinder in addition to the welding equipment. The
mill serves as my drill press. For most jobs a good mill/drill would also
do. A larger bandsaw would be better, but what I have was enough to make a
hydraulic bucket loader attachment for my small tractor and a bandsaw lumber
mill, plus lab prototypes for aerospace projects and various custom
automotive tools. I have other equipment including a surface grinder, rotary
indexers and sheet metal shear/brake but those are the essentials. To
oversimplify the bandsaw and mill make the framework, the lathe makes the
moving parts.

To some extent the framework can be plate sawn or torched to shape and the
bolt and bearing holes done on a drill press, preferably after welding which
may shift nearby holes. Drilling two side plates clamped together makes the
hole locations identical if not exactly where intended. High tensile bolts
like US Grade 5 and 8 can serve as pivots though they aren't ideal for
diameter, length or surface finish. Machine tools give you many more options
and make putting bearing holes right where you want them and all parallel
(for the toggle linkage) much easier.

Here's a tungsten carbide hardface meant for rock impacts that can be
applied with acetylene:
https://tnfarriersupply.com/products/black-diamond-borium-rods

"Richard Smith" wrote in message news:m1il2sh6wq.fsf@void.com...

The "AR400" I think that is for excavator bucket lining and the like -
nothing like as hard as a rock crusher working face needs to be?

----------------------------

It's a machinable high strength steel that I can obtain locally in small
cut-offs.
https://www.practicalmachinist.com/forum/threads/milling-ar-400-need-some-advice-please.239548/

Another is 5160 leaf spring stock, but it's limited in sizes. I made a D
step drill from O-1 drill rod to open a leaf spring shackle hole from 1/2"
to 5/8" that cut well enough after the second heat treating attempt. The kid
just had to lift his truck higher than his father's which was on a
commercial lift kit, so he had a higher lift kit fabricated and it came with
5/8" U bolts. As usual the answer was to call Jim for help.

If they are available wherever the H you are (Coober Pedy, Alice Springs?)
they might be strong plus tough enough for the toggle linkage and blade
bodies though not the cutting face which you suggested hardfacing.

Notes from yesterday "YouTube'ing"...

vvvvvvvv

Notes from yesterday "YouTube".
Various manufacturers talking.
[Came across the eccentric wheel crusher]

Jaw crushers are tough - the reality. For primary crushing cone /
gyrating crushers have the numbers for throughput and the crushing
performance - but not that toughness. Much more vulnerable to
"uncrushable" debris, etc. - where damage sends up cost.

Impact crushers are found in bigger sizes.
Anyone wants a "one pass" large initial to fine final size.
Yes for small sizes / small operations.
Scale-up - still "one pass" - but wear goes against them, compared to
large crushing crushers.

Small-scale - gold prospectors sometimes improvise a chain-flail
impact crusher where deliberately nothing leaves the chamber until it
leaves with a throughflow of air as dust...

^^^^^^^^

For stemming you want a definite size distribution - a coarse (~ 4mm to
5mm ?) sharp grit - so much of above not relevant. Many "ore
extraction" applications - finer is better (?).

Heard of a roll crusher which apparently gives a lot of the throughput
close to the aim size (???).

On Thu, 15 Feb 2024 04:43:51 +0000
Richard Smith <null@void.com> wrote:

<snip>
>Heard of a roll crusher which apparently gives a lot of the throughput
>close to the aim size (???).

There are several old texts, compilations on Mining and such at
Archive.com. If you have any spare time nowadays :) For instance:

https://archive.org/details/miningscientific96sanfuoft/page/154/mode/2up

Came across them awhile back while searching for some old info...

--
Leon Fisk
Grand Rapids MI

Leon Fisk <lfiskgr@gmail.invalid> writes:

> On Thu, 15 Feb 2024 04:43:51 +0000
> Richard Smith <null@void.com> wrote:
>
> <snip>
>>Heard of a roll crusher which apparently gives a lot of the throughput
>>close to the aim size (???).
>
> There are several old texts, compilations on Mining and such at
> Archive.com. If you have any spare time nowadays :) For instance:
>
> https://archive.org/details/miningscientific96sanfuoft/page/154/mode/2up
>
> Came across them awhile back while searching for some old info...

Thanks for that link.

At the mine yesterday someone told me

* he appreciated my links to YouTube videos on my webpage
http://www.weldsmith.co.uk/tech/minerals/240205_yt_goldmine/240205_yt_goldmine.html
"Opening My Gold Mine!" series
and had got up to 8 of the 17 of the series

* he and his father have a "hammer mill" - a high-speed (?) impact
crusher

* the output of that goes to some "California stamps" they made

* they have some 5% cassiterite (tin oxide) - ie. notably excellent -
ore to work which they obtained from a mine a few decades ago

So that's opened another conversation.

Rich Smith

"Richard Smith" wrote in message news:m1frxs7idr.fsf@void.com...

Leon Fisk <lfiskgr@gmail.invalid> writes:

> On Thu, 15 Feb 2024 04:43:51 +0000
> Richard Smith <null@void.com> wrote:
>
> <snip>
>>Heard of a roll crusher which apparently gives a lot of the throughput
>>close to the aim size (???).
>
> There are several old texts, compilations on Mining and such at
> Archive.com. If you have any spare time nowadays :) For instance:
>
> https://archive.org/details/miningscientific96sanfuoft/page/154/mode/2up
>
> Came across them awhile back while searching for some old info...

Thanks for that link.

At the mine yesterday someone told me

* he appreciated my links to YouTube videos on my webpage
http://www.weldsmith.co.uk/tech/minerals/240205_yt_goldmine/240205_yt_goldmine.html
"Opening My Gold Mine!" series
and had got up to 8 of the 17 of the series

* he and his father have a "hammer mill" - a high-speed (?) impact
crusher

* the output of that goes to some "California stamps" they made

* they have some 5% cassiterite (tin oxide) - ie. notably excellent -
ore to work which they obtained from a mine a few decades ago

So that's opened another conversation.

Rich Smith
------------------------------------

My impression is that stamping mills have the advantage of being simple and
easily maintainable without needing a machine shop, perhaps only basic
blacksmithing equipment (or acetylene) suffices. When I study early 1800's
tech I look for what they needed to make it. Steam engines languished at a
primitive level for a century for lack of machine tools.

While not specific to mining, the forge that accompanied horse artillery is
a well described example of a self-sufficient portable metalworking
capability.
https://en.wikipedia.org/wiki/Traveling_forge
The original Army manual lists the equipment but not how it was used. In
addition to horseshoeing they had battle damage to their and other vehicles
to repair.

A modern version is the rather minimal gear blacksmiths carry to demonstrate
at fairs and festivals.

"Richard Smith" wrote in message news:m1y1bm2v7c.fsf@void.com...

Jaw crushers are tough - the reality. For primary crushing cone /
gyrating crushers have the numbers for throughput and the crushing
performance - but not that toughness. Much more vulnerable to
"uncrushable" debris, etc. - where damage sends up cost.

Impact crushers are found in bigger sizes.
Anyone wants a "one pass" large initial to fine final size.
Yes for small sizes / small operations.
Scale-up - still "one pass" - but wear goes against them, compared to
large crushing crushers.

Small-scale - gold prospectors sometimes improvise a chain-flail
impact crusher where deliberately nothing leaves the chamber until it
leaves with a throughflow of air as dust...

^^^^^^^^

For stemming you want a definite size distribution - a coarse (~ 4mm to
5mm ?) sharp grit - so much of above not relevant. Many "ore
extraction" applications - finer is better (?).

Heard of a roll crusher which apparently gives a lot of the throughput
close to the aim size (???).

----------------------------
I've been waiting for and researching the question of what you need to build
such machinery, and haven't found good answers because it depends so much on
what you want/need to do, and how much size capacity you are willing to buy
new or can find locally used. Metalworking can become an expensive hobby
depending on the size, power and complexity of your designs.

"Jim Wilkins" wrote in message news:uqsrip$11g2t$1@dont-email.me...

I've been waiting for and researching the question of what you need to build
such machinery, and haven't found good answers because it depends so much on
what you want/need to do, and how much size capacity you are willing to buy
new or can find locally used. Metalworking can become an expensive hobby
depending on the size, power and complexity of your designs.

------------------------------

Here is a good example. Required horsepower and speed determine shaft
torque, and the dimensions of the appropriate shaft partly determine lathe
size, the spindle bore for long shafts and distance between centers for
short ones.
https://www.plantengineering.com/articles/relationship-of-torque-and-shaft-size/

Buying expensive new drive components can reduce or eliminate custom
machining, using salvaged ones increases it.

Likewise the distance between bearing bores that must be parallel determines
milling machine table size. Building larger with self-aligning pillow blocks
can bring fussy alignment issues and higher maintenance.

"Jim Wilkins" <muratlanne@gmail.com> writes:

> "Jim Wilkins" wrote in message news:uqsrip$11g2t$1@dont-email.me...
>
> I've been waiting for and researching the question of what you need to build
> such machinery, and haven't found good answers because it depends so much on
> what you want/need to do, and how much size capacity you are willing to buy
> new or can find locally used. Metalworking can become an expensive hobby
> depending on the size, power and complexity of your designs.
>
> ------------------------------
>
> Here is a good example. Required horsepower and speed determine shaft
> torque, and the dimensions of the appropriate shaft partly determine
> lathe size, the spindle bore for long shafts and distance between
> centers for short ones.
> https://www.plantengineering.com/articles/relationship-of-torque-and-shaft-size/
>
> Buying expensive new drive components can reduce or eliminate custom
> machining, using salvaged ones increases it.
>
> Likewise the distance between bearing bores that must be parallel
> determines milling machine table size. Building larger with
> self-aligning pillow blocks can bring fussy alignment issues and
> higher maintenance.

I was thinking of a small device to start with.
Maybe opening to jaw area is very few inches wide and gap.
If objective is "grit" around 6mm / 1/4inch, the stroke of the jaws
could be small?
Limited throughput, but advantages?
Looking to get a sack of the coarse grit for "stemming"
(can go down into the mine in the skip down the shaft)

Haven't developed anything more at the moment.
Line-boring the bearings yes.
How to machine and eccentric - realise don't know how to do that.
Visualise having two centres each end for between-centres.
Challenge is their axis, offset being on the same radius (the radial
direction) and radial offset.
Must look-up how that is done...

On 2/22/2024 10:15 AM, Richard Smith wrote:
> "Jim Wilkins" <muratlanne@gmail.com> writes:
>
>> "Jim Wilkins" wrote in message news:uqsrip$11g2t$1@dont-email.me...
>>
>> I've been waiting for and researching the question of what you need to build
>> such machinery, and haven't found good answers because it depends so much on
>> what you want/need to do, and how much size capacity you are willing to buy
>> new or can find locally used. Metalworking can become an expensive hobby
>> depending on the size, power and complexity of your designs.
>>
>> ------------------------------
>>
>> Here is a good example. Required horsepower and speed determine shaft
>> torque, and the dimensions of the appropriate shaft partly determine
>> lathe size, the spindle bore for long shafts and distance between
>> centers for short ones.
>> https://www.plantengineering.com/articles/relationship-of-torque-and-shaft-size/
>>
>> Buying expensive new drive components can reduce or eliminate custom
>> machining, using salvaged ones increases it.
>>
>> Likewise the distance between bearing bores that must be parallel
>> determines milling machine table size. Building larger with
>> self-aligning pillow blocks can bring fussy alignment issues and
>> higher maintenance.
>
> I was thinking of a small device to start with.
> Maybe opening to jaw area is very few inches wide and gap.
> If objective is "grit" around 6mm / 1/4inch, the stroke of the jaws
> could be small?
> Limited throughput, but advantages?
> Looking to get a sack of the coarse grit for "stemming"
> (can go down into the mine in the skip down the shaft)
>
> Haven't developed anything more at the moment.
> Line-boring the bearings yes.
> How to machine and eccentric - realise don't know how to do that.
> Visualise having two centres each end for between-centres.
> Challenge is their axis, offset being on the same radius (the radial
> direction) and radial offset.
> Must look-up how that is done...
>

When I've needed an eccentric I set my piece up in a 4 jaw chuck
offset the needed distance . If short , you can machine it without a
center on the open end . If you need length you have to be careful to
index your stock so the offset centers are aligned .
--
Snag
"They may take our lives but
they'll never take our freedom."
William Wallace

"Richard Smith" wrote in message news:m1edd479wi.fsf@void.com...

I was thinking of a small device to start with.
Maybe opening to jaw area is very few inches wide and gap.
If objective is "grit" around 6mm / 1/4inch, the stroke of the jaws
could be small?
Limited throughput, but advantages?
Looking to get a sack of the coarse grit for "stemming"
(can go down into the mine in the skip down the shaft)

Haven't developed anything more at the moment.
Line-boring the bearings yes.
How to machine and eccentric - realise don't know how to do that.
Visualise having two centres each end for between-centres.
Challenge is their axis, offset being on the same radius (the radial
direction) and radial offset.
Must look-up how that is done...

----------------------------

That's the sort of question we can help with. The simple way is to lightly
mark the centers on both sides, clamp it from turning on a flat surface and
scribe a horizontal line through both centers. Dividers can then scribe the
offset radius on both ends. Make a small punch mark at the intersection,
chuck the blank in a 4-jaw lathe chuck and adjust the jaws until a pointed
rod pushed against the offset center doesn't wiggle as the chuck is rotated.
Then the eccentric can be turned around its offset center.

Scribing and punching usually gets me within about 0.1mm of the intended
location.

This describes the methods and the necessary, often cheap used, equipment
required. It's mainly Euclidian geometry.
https://www.amazon.com/Accurate-Tool-Work-Clarence-Goodrich/dp/B004QZ9Y5M

"Richard Smith" wrote in message news:m1edd479wi.fsf@void.com...

Haven't developed anything more at the moment.
Line-boring the bearings yes.

----------------------------

Modern lathes aren't as easily set up for line boring or other milling-type
operations as older designs like the Myfords with tee slots for clamping
bolts on the flat top of the carriage.

Myford lathes seem as popular in Britain as old South Bends (like mine) are
in the USA. Perhaps Tony could help you with their capabilities and
limitations.

On 22/02/2024 23:14, Jim Wilkins wrote:
> "Richard Smith"  wrote in message news:m1edd479wi.fsf@void.com...
>
> Haven't developed anything more at the moment.
> Line-boring the bearings yes.
>
> ----------------------------
>
> Modern lathes aren't as easily set up for line boring or other
> milling-type operations as older designs like the Myfords with tee
> slots for clamping bolts on the flat top of the carriage.
>
> Myford lathes seem as popular in Britain as old South Bends (like
> mine) are in the USA. Perhaps Tony could help you with their
> capabilities and limitations.
>
I'm not so sure about that, my Harrison M300 has a flat top cross slide
with a dovetail section to allow add ons such as rear tool posts to be
clamped to it. When I wanted to do some line boring I made a T slot
table to clamp to it and got on with the job. I think many modern lathes
do similar. That's a bit different to having T slots in the cross slide
as standard which my Kerry 1140 has 2 and an older lathe but the table
was an easy add on to make.

"David Billington" wrote in message news:ur8mg6$53it$1@dont-email.me...

>
I'm not so sure about that, my Harrison M300 has a flat top cross slide
with a dovetail section to allow add ons such as rear tool posts to be
clamped to it. When I wanted to do some line boring I made a T slot
table to clamp to it and got on with the job. I think many modern lathes
do similar. That's a bit different to having T slots in the cross slide
as standard which my Kerry 1140 has 2 and an older lathe but the table
was an easy add on to make.

------------------------

My first student Bridgeport project was a dovetail base for a milling
attachment for the 6" lathe whose worn bed I had milled straight on a big
horizontal mill. The task wasn't too difficult and functioned as expected
though the project convinced me I needed a larger lathe, as that little one
was fine for brass and aluminum but could barely cut mild steel. I found the
10" South Bend and haven't regretted it. The little one turns much faster
and I put a 1/2" drill chuck on it for safety and use it for polishing and
drilling deep grease holes in axles.

It seems the 10" lathe was meant for one-offs and small batches for a tool
maker, inventor or model shop and companies doing higher volume commercial
work chose larger lathes, like 15". Likewise I've seen mill-drills and
smaller knee mills such as my Clausing only in shops that did little
milling, the Bridgeport size is standard. A smaller second-hand machine may
not have as much wear as one suited to production work.

Snag <Snag_one@msn.com> writes:

>>> ...
>> ...

> When I've needed an eccentric I set my piece up in a 4 jaw chuck
> offset the needed distance . If short , you can machine it without a
> center on the open end . If you need length you have to be careful
> to index your stock so the offset centers are aligned .

Thanks Snag.
I can "see" that.
Presumably can wind the saddle of the lathe along with a
test-dial-indicator against the now offset shaft, checking by zero
deflection that the shaft is still on the same axis?
"Fiddle" until you find a perfect alignment then get machining?
For the longer shafts of the eccentric of a jaw-crusher you would drill
a small centre-taper and have the tailstock supporting?

"Jim Wilkins" <muratlanne@gmail.com> writes:

>>> ...
>> ...
>
> That's the sort of question we can help with. The simple way is to
> lightly mark the centers on both sides, clamp it from turning on a
> flat surface and scribe a horizontal line through both
> centers. Dividers can then scribe the offset radius on both ends. Make
> a small punch mark at the intersection, chuck the blank in a 4-jaw
> lathe chuck and adjust the jaws until a pointed rod pushed against the
> offset center doesn't wiggle as the chuck is rotated. Then the
> eccentric can be turned around its offset center.
>
> Scribing and punching usually gets me within about 0.1mm of the
> intended location.
>
> This describes the methods and the necessary, often cheap used,
> equipment required. It's mainly Euclidian geometry.
> https://www.amazon.com/Accurate-Tool-Work-Clarence-Goodrich/dp/B004QZ9Y5M

Right...
Yup seeing myself going around the local college and using a
surface-plate and the vertical gauge with the scribing edge.

Thanks everyone for coming back on this one.
Not sure can take it anywhere at mo. - but appreciate knowing how I
would go about it...

"Richard Smith" wrote in message news:m1r0h37ii3.fsf@void.com...

"Jim Wilkins" <muratlanne@gmail.com> writes:
>>> ...
> This describes the methods and the necessary, often cheap used,
> equipment required. It's mainly Euclidian geometry.
> https://www.amazon.com/Accurate-Tool-Work-Clarence-Goodrich/dp/B004QZ9Y5M

Right...
Yup seeing myself going around the local college and using a
surface-plate and the vertical gauge with the scribing edge.

---------------------------
I assembled a good set of layout equipment at low cost because CNC has made
it obsolete.

The old timers came up with many ways to do very accurate work using simpler
machine tools without digital readouts. The US watchmaking industry was
especially skilled at making very precise fixturing for rapid mass
production on hobbyist-sized lathes. Later the auto makers met the challenge
but their methods involved large custom machinery. I apprenticed at a
company that supplied them with custom equipment.

That company welded the framework and then we assemblers used manual methods
to locate and bolt on the components. The machines tested electronic
components for emission controls etc so they didn't have much mechanical
power transmission, except parts handlers. I have to use the old methods
when my projects are too large for my machine tools, like the center splice
on the 16 foot long, 200 lb gantry hoist track.

I just bought a 2000 Kg hanging scale for it, for $90, since the logs
waiting to become beams and boards weigh well over the 1000 Kg capacity of
my older scale. I consider the cost to be medical insurance, to avoid
accidents from overloads.

On 2/23/2024 1:19 AM, Richard Smith wrote:
> Snag <Snag_one@msn.com> writes:
>
>>>> ...
>>> ...
>
>> When I've needed an eccentric I set my piece up in a 4 jaw chuck
>> offset the needed distance . If short , you can machine it without a
>> center on the open end . If you need length you have to be careful
>> to index your stock so the offset centers are aligned .
>
> Thanks Snag.
> I can "see" that.
> Presumably can wind the saddle of the lathe along with a
> test-dial-indicator against the now offset shaft, checking by zero
> deflection that the shaft is still on the same axis?

I was thinking more of an index line down the length of the stock
aligned with one of the chuck jaws as a reference , but a pass with the
DI would be a good way to insure the alignment .

> "Fiddle" until you find a perfect alignment then get machining?
> For the longer shafts of the eccentric of a jaw-crusher you would drill
> a small centre-taper and have the tailstock supporting?
>

Actually holding the part on offset centers and using a drive dog would
work well too . But yes , you have the idea I was trying to convey .
I used the chuck to offset the cam on my home made QCTP but it's only
a couple of inches long .
--
Snag
"They may take our lives but
they'll never take our freedom."
William Wallace

"Richard Smith" wrote in message news:m1msrr7iga.fsf@void.com...

Thanks everyone for coming back on this one.
Not sure can take it anywhere at mo. - but appreciate knowing how I
would go about it...

------------------------------

The decisions break down to buy, build or find another interest. Build
involves an investment in space-consuming machinery that hopefully retains
or gains resale value (that's the excuse). For me the advantage of learning
machining was becoming able to take on all of a project instead of only the
electrical part. It might not have been done if it required assembling,
coordinating and paying a team.

On the better-run projects I've seen each member had a self-contained
portion of it that didn't need much interaction (disagreement) with others.
Dealing with the company machine shop required defining problems in their
terms, machine to these dimensions and tolerances, instead of expecting them
to come up with a solution to someone else's problem. That was usually my
job.

"Snag" wrote in message news:ura58d$i0ak$1@dont-email.me...

On 2/23/2024 1:19 AM, Richard Smith wrote:
> Snag <Snag_one@msn.com> writes:
>
>>>> ...
>>> ...
>
>> When I've needed an eccentric I set my piece up in a 4 jaw chuck
>> offset the needed distance . If short , you can machine it without a
>> center on the open end . If you need length you have to be careful
>> to index your stock so the offset centers are aligned .
>
> Thanks Snag.
> I can "see" that.
> Presumably can wind the saddle of the lathe along with a
> test-dial-indicator against the now offset shaft, checking by zero
> deflection that the shaft is still on the same axis?

I was thinking more of an index line down the length of the stock
aligned with one of the chuck jaws as a reference , but a pass with the
DI would be a good way to insure the alignment .

> "Fiddle" until you find a perfect alignment then get machining?
> For the longer shafts of the eccentric of a jaw-crusher you would drill
> a small centre-taper and have the tailstock supporting?
>

Actually holding the part on offset centers and using a drive dog would
work well too . But yes , you have the idea I was trying to convey .
I used the chuck to offset the cam on my home made QCTP but it's only
a couple of inches long .
Snag
"They may take our lives but
they'll never take our freedom."
William Wallace

--------------------------------
That's in the class of problems I assume can be solved when making it, cross
that bridge... They don't hold up the design process, though I may make them
first to be sure. If someone else has done it there must be a way. The
solution may be having to make a locating fixture, as for machining a
crankshaft.
https://modelenginenews.org/techniques/crankshafts.html

I use 5C collets in square or hex blocks to accurately machine the ends of
round rods. Vee blocks on a mill would do for eccentric center holes in
fairly short shafts.

On Fri, 23 Feb 2024 07:19:14 +0000, Richard Smith <null@void.com>
wrote:

>Snag <Snag_one@msn.com> writes:
>
>>>> ...
>>> ...
>
>> When I've needed an eccentric I set my piece up in a 4 jaw chuck
>> offset the needed distance . If short , you can machine it without a
>> center on the open end . If you need length you have to be careful
>> to index your stock so the offset centers are aligned .
>
>Thanks Snag.
>I can "see" that.
>Presumably can wind the saddle of the lathe along with a
>test-dial-indicator against the now offset shaft, checking by zero
>deflection that the shaft is still on the same axis?
>"Fiddle" until you find a perfect alignment then get machining?
>For the longer shafts of the eccentric of a jaw-crusher you would drill
>a small centre-taper and have the tailstock supporting?
IIRC that is how I made the eccentrics for my compost screen shaker. I
started with a short length of round stock offset in the four jaw,
centre drilled the right end, turned down the mid section; then
through drilled for the shaft and cut it in half andused the small
diameter in the fixed journals and the larger eccentrics in the screen
frame rails. The two sections are keyed to the driving shaft by set
screws in dimples in the shaft
Now that the City has institutrd a green bin program I will probably
transfer my screening plant to Junior who lives out of town.