rock jaw-crusher, other rock crushers

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".]

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.]

Current practice seems to be to use "Nonel" (non-electric) detonators. Brilliant explanation at YouTube channel

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?

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:

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?

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It's a machinable high strength steel that I can obtain locally in small cut-offs.

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 (???).

<snip>

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

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
  formatting link
  "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

Thanks for that link.

At the mine yesterday someone told me

• he appreciated my links to YouTube videos on my webpage
  formatting link
  "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.

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.

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.

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.

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 .

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.

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.

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.

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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.

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?

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...