We covered like topic before - buck/boost.
Just need to "buck" - reduce voltage from 18V to 12V
In your opinions - small fitment going into battery "shoe" of 12V tool
adapting to fitting an 18V battery pack and having the "buck"
volts-to-amps trade - is viable?
They exist and are offered - eg. on Alibaba.

Want an SDS drill small enough to carry in a shoulder-bag through a mine
- but use existing 18V batteries - not expensive option of starting
stock of 12V batteries.
For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
wedges. Into hard granite - so needs a "serious" hammer-action drill.

Maybe have to get 18V drill.
Helpful advice this morning - for same voltage - 18V to 18V - has
straight-through couplings going eg. DeWalt to Makita.
So can choose smallest neatest 18V tool.

Thanks in advance,
Rich Smith

"Richard Smith" wrote in message news:m17cio63li.fsf@void.com...

We covered like topic before - buck/boost.
Just need to "buck" - reduce voltage from 18V to 12V
In your opinions - small fitment going into battery "shoe" of 12V tool
adapting to fitting an 18V battery pack and having the "buck"
volts-to-amps trade - is viable?
They exist and are offered - eg. on Alibaba.

Want an SDS drill small enough to carry in a shoulder-bag through a mine
- but use existing 18V batteries - not expensive option of starting
stock of 12V batteries.
For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
wedges. Into hard granite - so needs a "serious" hammer-action drill.

Maybe have to get 18V drill.
Helpful advice this morning - for same voltage - 18V to 18V - has
straight-through couplings going eg. DeWalt to Makita.
So can choose smallest neatest 18V tool.

Thanks in advance,
Rich Smith

----------------------------
Viable - yes, easy - perhaps not. That's the sort of thing I do. An adapter
to plug into to the 12V tool could be made from a dead battery pack, though
you have to strip the batteries out while keeping the retaining latch, and
the contacts may depend on the cells (or waxed dowels) to stay in place.
Flexible silicone-insulated wire is very helpful to reduce strain on
unintended solder connections. The straight oval Makita packs unlatch to
disassemble.

Then you can measure the stall current of the motor and select a converter
that can handle it. In my experience the cheap import voltage converters
aren't too hard to fry from an overload and their max current rating is only
with external fan cooling. Be sure to fuse the wiring.

Unless I carve a connector holder on the milling machine my DIY battery pack
connectors are thin strips of copper or brass jammed into the slots, since
the packs don't usually reversibly disassemble to allow soldering
internally. Nickel strips sold as weld-on tabs for replacement battery cells
might survive dampness better. The charger contacts could be wired to bring
out power from a plugged-in battery though that might be too awkward and
vulnerable down in the mine.

I mark the battery terminals with red (+) and black (-) nail polish to avoid
accidents. Asking a female clerk for help finding it can be an adventure.

The simpler approach may be to make a corded portable battery pack from a
12V, 18A AGM or LiFeP04 enclosed in a waterproof (?) plastic ammo box, and
parallel the tool's battery contacts with a pigtail power cord. Anderson or
Powerpole PP45 connectors work well to interconnect DC power because they
are non-gendered and insulated on both sides when unplugged. Plug and socket
connectors aren't meant to safely pass power in both directions, to charge
and discharge the battery. For wet locations MC4 connectors for solar panels
are waterproof when connected, and safe to handle when unplugged.

If you are converting from old dead NiCads to currently available NiMH
packs, the old charger may or may not damage them by overcharging. I bought
a cheap compatible Vinida charger for my converted DeWalt.

Good Luck!

"Richard Smith" wrote in message news:m17cio63li.fsf@void.com...

Want an SDS drill small enough to carry in a shoulder-bag through a mine
- but use existing 18V batteries - not expensive option of starting
stock of 12V batteries.
For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
wedges. Into hard granite - so needs a "serious" hammer-action drill.

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

This is what I have and it's barely fast enough in granite for homeowner
use:
https://usatoolsinc.com/makita-1-1-2-in-rotary-hammer-spline-ac-dc-hr3851-discontinued-replaced-by-hr4041c/

When it broke the contractor replaced it with a larger Hitachi. He had
bought it to run pipes and conduit through concrete, and complained about
how slow it was. I'm well equipped partly because friends give me stuff they
can't fix.

Must take my 240V power tool to the mine and at the surface try it on
pieces of granite from the mine.
Calibrate my judgement of what an impact energy in J(oules) relates to
as a drilling ability.
Looking to identify suitable battery-powered drill.
The holes for the "feathers" need to be 2inch to 3inch deep - not a lot.
To have a smaller lighter drill (the machine), could be willing to
pilot-drill and full-size drill.

Thanks for comment I read as being that to "buck" in such a small space
- between an 18V battery and a fitting into the 12V "shoe" - is not
likely to be a robust device.

Rich S

On Wed, 28 Feb 2024 14:55:05 +0000, Richard Smith <null@void.com>
wrote:

>We covered like topic before - buck/boost.
>Just need to "buck" - reduce voltage from 18V to 12V
>In your opinions - small fitment going into battery "shoe" of 12V tool
>adapting to fitting an 18V battery pack and having the "buck"
>volts-to-amps trade - is viable?
>They exist and are offered - eg. on Alibaba.
>
>Want an SDS drill small enough to carry in a shoulder-bag through a mine
>- but use existing 18V batteries - not expensive option of starting
>stock of 12V batteries.
>For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
>wedges. Into hard granite - so needs a "serious" hammer-action drill.
>
>Maybe have to get 18V drill.
>Helpful advice this morning - for same voltage - 18V to 18V - has
>straight-through couplings going eg. DeWalt to Makita.
>So can choose smallest neatest 18V tool.
>
>Thanks in advance,
>Rich Smith
Just run the 12 volt drill on 18 volts. A friend built an
entireZenith 701 airplane using a 7.2 volt cordless drill wired to a
12 volt car battery Thousands of holes - the drill ran a bit faster
than it was designed to run but that was not a problem with 1/8" bits.
I imagine the SDS hammer drill would just gain a bit of extra power
from the extra 6 volts.

On 2/28/2024 12:06 PM, Jim Wilkins wrote:
> "Richard Smith"  wrote in message news:m17cio63li.fsf@void.com...
>
> Want an SDS drill small enough to carry in a shoulder-bag through a mine
> - but use existing 18V batteries - not expensive option of starting
> stock of 12V batteries.
> For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
> wedges.  Into hard granite - so needs a "serious" hammer-action drill.
>
> ------------------------
>
> This is what I have and it's barely fast enough in granite for homeowner
> use:
> https://usatoolsinc.com/makita-1-1-2-in-rotary-hammer-spline-ac-dc-hr3851-discontinued-replaced-by-hr4041c/
>
>
> When it broke the contractor replaced it with a larger Hitachi. He had
> bought it to run pipes and conduit through concrete, and complained
> about how slow it was. I'm well equipped partly because friends give me
> stuff they can't fix.
>

I too have been the recipient of tools the previous owner couldn't fix
.. Mostly chainsaws and other small engine powered equipment . These
hillbillies aren't always big on routine maintenance .
--
Snag
"They may take our lives but
they'll never take our freedom."
William Wallace

Richard Smith <null@void.com> wrote:
> We covered like topic before - buck/boost. Just need to "buck" -
> reduce voltage from 18V to 12V In your opinions - small fitment
> going into battery "shoe" of 12V tool adapting to fitting an 18V
> battery pack and having the "buck" volts-to-amps trade - is viable?
> ...

Possible, as Jim Wilkins said, and maybe viable, but likely to be a
jury-rigged lashup. Do you already have a 12V SDS drill on hand, that
you want to adapt? If so, get a motorcycle-size 12V battery (like Jim
Wilkins mentioned) or just use 18V straight (like Clare Snyder
suggested). If buying new and have a choice, go with a modern 20 V or
higher voltage SDS drill, or if 18V is de rigueur, an 18V unit.

> Want an SDS drill small enough to carry in a shoulder-bag through a
> mine - but use existing 18V batteries - not expensive option of
> starting stock of 12V batteries.

I expect that the lighter the tool, the longer it will take, if it
works at all, and in any case, extra batteries will make up much of
the weight you need to carry. BTW, how long would an extension cord
need to be? A cord might be better use of money. Am I correct in
surmising a gas-powered generator is out of the question due to its
exhaust, or is the mine's air circulation just peachy?

> For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
> wedges. Into hard granite - so needs a "serious" hammer-action drill.

If you are drilling under a dozen holes, get a sledge and a star drill
and manually make the holes.

"Richard Smith" wrote in message news:m134tc5sng.fsf@void.com...

Thanks for comment I read as being that to "buck" in such a small space
- between an 18V battery and a fitting into the 12V "shoe" - is not
likely to be a robust device.

Rich S
-------------------------------
I don't have experience with the higher powered buck converters except for
this, which may be more money and complexity and less ruggedness than you
want:
https://www.amazon.com/RD-Constant-Step-Down-Converter-Voltmeter/dp/B099YZFX34

A metal case is available, for dry indoor use. It's a very useful tool for
experimenting, component testing and maintaining batteries of all types and
voltages, AAA to golf cart. I've run it near full current for hours
recharging a deep cycle battery after a capacity test.

The ones that failed were >10A buck-boost converters, a different circuit.
The smaller 4-5A buck and buck-boost converters have been fine.

A freshly charged NiCad / NiMH can be quite a few volts higher than its
nominal voltage. The voltage from my "14.4V" charger reaches 22V just before
full charge shutoff, and the battery measures 17-18V. A meter or storage
scope shows the small voltage steps down as each cell fully charges and
begins generating oxygen instead. They set the amount of anode and cathode
material unequal to make it generate oxygen which recombines and raises the
temperature before hydrogen which would have to vent. The extra contact is
for an internal temperature sensor. AGMs do the same, the reason their
charging current should be limited.

I wasn't going to suggest running on the higher voltage because I haven't
tried it, my second hand cordless drills aren't beat-up enough to sacrifice
for a data point. Drilling thin aluminum isn't like chugging several inches
into granite. The hole needs to be about as deep as the length of the wedge.

"Snag" wrote in message news:uroeod$4m3m$1@dont-email.me...

I too have been the recipient of tools the previous owner couldn't fix
.. Mostly chainsaws and other small engine powered equipment . These
hillbillies aren't always big on routine maintenance .
Snag
-----------------------

My first chainsaw which I used until parts became unavailable was a
combination of two basket cases (same peach basket), one that wore out and
another a tree had fallen on and cracked the case. The fix wasn't apparent
to the owner.

"James Waldby" wrote in message news:urohgh$571k$1@dont-email.me...

If you are drilling under a dozen holes, get a sledge and a star drill
and manually make the holes.

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

Have you actually tried drilling granite that way?

On Wed, 28 Feb 2024 19:20:07 -0500, "Jim Wilkins"
<muratlanne@gmail.com> wrote:

>"Snag" wrote in message news:uroeod$4m3m$1@dont-email.me...
>
> I too have been the recipient of tools the previous owner couldn't fix
>. Mostly chainsaws and other small engine powered equipment . These
>hillbillies aren't always big on routine maintenance .
>Snag
>-----------------------
>
>My first chainsaw which I used until parts became unavailable was a
>combination of two basket cases (same peach basket), one that wore out and
>another a tree had fallen on and cracked the case. The fix wasn't apparent
>to the owner.
Like the "parts saw" I spent a dollar on a few years back. "Damned
thing won't run!" the fuel line was pinched between sections of the
case.

"Gerry" wrote in message news:icovtid681isu60r9lh6dbesghb6tc7j6j@4ax.com...

On Wed, 28 Feb 2024 19:20:07 -0500, "Jim Wilkins"
<muratlanne@gmail.com> wrote:

>"Snag" wrote in message news:uroeod$4m3m$1@dont-email.me...
>
> I too have been the recipient of tools the previous owner couldn't fix
>. Mostly chainsaws and other small engine powered equipment . These
>hillbillies aren't always big on routine maintenance .
>Snag
>-----------------------
>
>My first chainsaw which I used until parts became unavailable was a
>combination of two basket cases (same peach basket), one that wore out and
>another a tree had fallen on and cracked the case. The fix wasn't apparent
>to the owner.
Like the "parts saw" I spent a dollar on a few years back. "Damned
thing won't run!" the fuel line was pinched between sections of the
case.

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

I've done that with the kill switch wire, which has soft high temperature
silicone insulation.

I bought a cheap 'broken' floor jack that needed a 70 cent snap ring to keep
a lift arm from popping off. I bought a $300 VW Beetle convertible that was
making an alarming noise in the engine area until I tightened the loose
bumper bolts.

On Wed, 28 Feb 2024 21:29:27 -0500, "Jim Wilkins"
<muratlanne@gmail.com> wrote:

>"Gerry" wrote in message news:icovtid681isu60r9lh6dbesghb6tc7j6j@4ax.com...
>
>On Wed, 28 Feb 2024 19:20:07 -0500, "Jim Wilkins"
><muratlanne@gmail.com> wrote:
>
>>"Snag" wrote in message news:uroeod$4m3m$1@dont-email.me...
>>
>> I too have been the recipient of tools the previous owner couldn't fix
>>. Mostly chainsaws and other small engine powered equipment . These
>>hillbillies aren't always big on routine maintenance .
>>Snag
>>-----------------------
>>
>>My first chainsaw which I used until parts became unavailable was a
>>combination of two basket cases (same peach basket), one that wore out and
>>another a tree had fallen on and cracked the case. The fix wasn't apparent
>>to the owner.
>Like the "parts saw" I spent a dollar on a few years back. "Damned
>thing won't run!" the fuel line was pinched between sections of the
>case.
>
>-------------------------------
>
>I've done that with the kill switch wire, which has soft high temperature
>silicone insulation.
>
>I bought a cheap 'broken' floor jack that needed a 70 cent snap ring to keep
>a lift arm from popping off. I bought a $300 VW Beetle convertible that was
>making an alarming noise in the engine area until I tightened the loose
>bumper bolts.
Around thirty years ago L blew a whole three bucks on "some kind of
electric meter" a Fluke 77. Junior made his college instructor jealous
when he started taking it to class!

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

> If you are drilling under a dozen
> holes, get a sledge and a star drill
> and manually make the holes.
>
> ------------------------
>
> Have you actually tried drilling granite that way?

I haven't.
I have heard of star drills.
I wondered whether for 10mm (3/8") a lump-hammer and a said star-drill
would work...
But haven't acted on in - even looked it up, whether currently available.

The granite
This type of drill
http://www.weldsmith.co.uk/tech/minerals/condurrow/231207_rockdrill1st/231224_holman_silver_900.html
(powerful)
could not run a 4-carbide-tips drillbit into the granite - had to use a
simple carbide chisel edged drill.

no@no.no (James Waldby) writes:

> Richard Smith <null@void.com> wrote:
>> We covered like topic before - buck/boost. Just need to "buck" -
>> reduce voltage from 18V to 12V In your opinions - small fitment
>> going into battery "shoe" of 12V tool adapting to fitting an 18V
>> battery pack and having the "buck" volts-to-amps trade - is viable?
>> ...
>
> Possible, as Jim Wilkins said, and maybe viable, but likely to be a
> jury-rigged lashup. Do you already have a 12V SDS drill on hand, that
> you want to adapt? If so, get a motorcycle-size 12V battery (like Jim
> Wilkins mentioned) or just use 18V straight (like Clare Snyder
> suggested). If buying new and have a choice, go with a modern 20 V or
> higher voltage SDS drill, or if 18V is de rigueur, an 18V unit.
>
>> Want an SDS drill small enough to carry in a shoulder-bag through a
>> mine - but use existing 18V batteries - not expensive option of
>> starting stock of 12V batteries.
>
> I expect that the lighter the tool, the longer it will take, if it
> works at all, and in any case, extra batteries will make up much of
> the weight you need to carry. BTW, how long would an extension cord
> need to be? A cord might be better use of money. Am I correct in
> surmising a gas-powered generator is out of the question due to its
> exhaust, or is the mine's air circulation just peachy?
>
>> For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
>> wedges. Into hard granite - so needs a "serious" hammer-action drill.
>
> If you are drilling under a dozen holes, get a sledge and a star drill
> and manually make the holes.

Can't carry a big battery down the mine and up the raises.
Ladders.

Any mention of "mains" - some parts of the mine are running with water.
Area doing work at moment is dry - solid granite no water penetration.
But simply cannot run 240V cable around.
110V - have to bring transformer, plus cables larger - again size and
weight, getting up and down ladders, etc.

Basically it's
* turn on the compressor and use a big rock-drill
* battery-powered "cordless" drill

Videos "gold mine" showed using cordless SDS drill for bit of
prospecting and chipping - in granite.
So seems is viable.

Going to try 240V SDS on surface with mine granite seeing reality of
what the drilling is like.

No chance of gasoline generator down mine.

"Gerry" wrote in message news:2c10ui1j3ct80i2of3n3hbj6nt641sqe9i@4ax.com...

Around thirty years ago L blew a whole three bucks on "some kind of
electric meter" a Fluke 77. Junior made his college instructor jealous
when he started taking it to class!

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

Good catch!

I got a pretty good deal on an older Fluke 8020 with a fading LCD display.
Fluke was happy to sell me a replacement LCD at a reasonable price. I also
picked up a Keithley DVM with the same problem and they laughed at me when I
asked about a replacement.

On Thu, 29 Feb 2024 07:16:29 +0000
Richard Smith <null@void.com> wrote:

<snip>
>Basically it's
>* turn on the compressor and use a big rock-drill
>* battery-powered "cordless" drill

If you have air available... there are smaller Rock Drills. For
instance:

https://power-technique.cp.com/en-us/products/handheld-pneumatic-us/sinkers-surface-rock-drills/cp-0014rr

IF you could run a gas machine... there's a gas powered Rock Drill
with lots of Ebay listings:

https://www.ebay.com/itm/176172437823

Suspect it is like a chainsaw, using mixed gas which doesn't sound to
air friendly in small areas...

--
Leon Fisk
Grand Rapids MI

"Richard Smith" wrote in message news:m15xy77p1u.fsf@void.com...

"Jim Wilkins" <muratlanne@gmail.com> writes:
> Have you actually tried drilling granite [with a star drill?]

I haven't.
I have heard of star drills.
I wondered whether for 10mm (3/8") a lump-hammer and a said star-drill
would work...
But haven't acted on in - even looked it up, whether currently available.

The granite
This type of drill
http://www.weldsmith.co.uk/tech/minerals/condurrow/231207_rockdrill1st/231224_holman_silver_900.html
(powerful)
could not run a 4-carbide-tips drillbit into the granite - had to use a
simple carbide chisel edged drill.

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

The Makita came with a 4-flute 1-1/4" bit that was useless on granite, but a
1/2" 2 flute cut fast enough for me, maybe an inch a minute. At least I
could see it move and powder flowing out. Neither the star drill nor the
one-hand corded hammer drill did more than mark the spot where it wasn't
making visible progress.

Plan B was to move the intact boulder, which got me started with portable
DIY gantry hoists and discussions that led to the Makita. When I decided to
cover my window trim with white aluminum I made a long enough bending brake
for it, and while working on it outside on the tailgate of the truck that
neighbor came over, saw it and offered to loan me his commercial 10' Tapco
brake. I happened into a neighborhood of very handy people, carpenters,
electricians, welders and mechanics. It's not odd that one owns a bucket
loader.
https://buymbs.com/c-108-tapco-brakes.aspx?gad_source=1

I had made a 1/8" nozzle for 3/8" vinyl tubing to forcefully breathe air
onto the gathered coals of last night's fire to start another, and it was
perfect for blowing the dust out of the drill hole without getting a
facefull of it.

Leon Fisk <lfiskgr@gmail.invalid> writes:

> On Thu, 29 Feb 2024 07:16:29 +0000
> Richard Smith <null@void.com> wrote:
>
> <snip>
>>Basically it's
>>* turn on the compressor and use a big rock-drill
>>* battery-powered "cordless" drill
>
> If you have air available... there are smaller Rock Drills. For
> instance:
>
> https://power-technique.cp.com/en-us/products/handheld-pneumatic-us/sinkers-surface-rock-drills/cp-0014rr
>
> ...

Solution come into view - will run an airline up the raise and use out
"Holman 303" sinker (jackhammer).
Very similar to the CP jackhammer you linked to.
So that is simply breaking the rocks with a chisel bit in a jackhammer.

On Fri, 01 Mar 2024 17:09:30 +0000
Richard Smith <null@void.com> wrote:

<snip>
>Solution come into view - will run an airline up the raise and use out
>"Holman 303" sinker (jackhammer).
>Very similar to the CP jackhammer you linked to.
>So that is simply breaking the rocks with a chisel bit in a jackhammer.

If you already have the equipment... might as well find out if it will
work for this job👍

--
Leon Fisk
Grand Rapids MI

Yes.
Also, might as well take extension-lead, the mains-powered SDS drill and
different sized drill-bits up to larger size and see what it will do
into the mine's granite from the at-surface pile.
Use what I have.
Develop an idea of what power is needed to drill what hole size - for
"feathers" to split rocks.
In case do have to get a cordless / battery powered drill.

On Fri, 01 Mar 2024 21:46:52 +0000
Richard Smith <null@void.com> wrote:

>Also, might as well take extension-lead, the mains-powered SDS drill and
>different sized drill-bits up to larger size and see what it will do
>into the mine's granite from the at-surface pile.
>Use what I have.
>Develop an idea of what power is needed to drill what hole size - for
>"feathers" to split rocks.
>In case do have to get a cordless / battery powered drill.

Very good idea👍

If you have any equipment rental companies in the area... may well be
worth trying-before-buying from them too.

--
Leon Fisk
Grand Rapids MI

On 28/02/2024 14:55, Richard Smith wrote:
> We covered like topic before - buck/boost.
> Just need to "buck" - reduce voltage from 18V to 12V

Not sure it's a good idea, see below and elsewhere, but if I were doing
it I'd go for a converter rated for at least 3 or 4 times the approx 10A
stall current, likely to cost around £30.

eg https://www.ebay.co.uk/itm/195597726440 DC 24V To DC 13.8V 40A 552W
Step Down Converter.

If you need plastic bits 3D printing can help. .stls of the common
connectors are readily available online, and though typically not very
good, they can be adapted.

The metal parts are usually not too hard to make with simple hand tools,
shears and files etc, and a heavy duty soldering iron.

> Want an SDS drill small enough to carry in a shoulder-bag through a mine
> - but use existing 18V batteries - not expensive option of starting
> stock of 12V batteries.
> For drilling holes - 10mm or 14mm for "feathers" - rock-splitting
> wedges. Into hard granite - so needs a "serious" hammer-action drill.

Most 12v drills are not going to be capable of that. In fact, most
18v/20v (typically they are the same, both batteries and tools, 20v just
sounds better) drills aren't going to find it easy, but ymmv.

Also a good hammer action is going to be heavy. Do you want SDS plus or
SDS Max?

I'd think a good SDS plus would be enough, something rated for 22m in
concrete, 16mm in steel.

You don't say what sort of 12v drill or 18v batteries you already have?

Peter Fairbrother

Current type:
Dewalt "XR" 18V.
Have for for current pistol-grip drill and driver - pair for
"general building work".

Thanks for linking me to a representative converter 20-ish volts to
13.8V which you reckon overall is up to the job - 40A device.

The tool gets bigger, it is marginally capable of the job, and it's good
money after bad.
Had the tool taken the batteries I have, I could have even piloted and
drilled to size to keep down the size of what I take dow the mine - this
being only for if get a granite boulder I need to break apart to make
easier to take away. Carry in a shoulder bag for if-and-when.
That "solution" gone.

I tool a 240V SDS drill to the mine
https://www.wickes.co.uk/Einhell-TE-RH-32E-5kg-Rotary-Hammer-Drill---1250W/p/208095
[successor model
https://www.einhell.co.uk/p/4257944-te-rh-32-4f-kit/
on maker's website]
and tried it on the mine granite brought to the surface.
That granite is hard tough stuff.
I will take a greater range of drill bits and form a map of what can be
done with that SDS drill.
This one is rated at "5J" (5 Joules of energy) for the impact action.

"I'd think a good SDS plus would be enough, something rated for 22m in
concrete, 16mm in steel."
I'd guess so - will update if find anything different.

Anyway, good news is plan for coming session - going to run an air-hose
up the raise and use a jackhammer to break up the rocks lying around on
that sub-level.

Explanation offered by an ex-miner why boulders there...
When used as a training mine, they showed going into the side of the
tunnel as if looking if lode went that way, and didn't use enough
blasting medium to shatter and break up the rock - said needed twice as
much blasting medium.

On 04/03/2024 09:07, Richard Smith wrote:
> Current type:
> Dewalt "XR" 18V.

DCH133 @ about £100 ?

There is granite and granite, but

https://www.youtube.com/watch?v=dNat1FCDfiA

Peter Fairbrother