Polishing and drilling marble slabs?
 

Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?

Does one use ordinary masonry drills?

Any undertakers out there?

Airy R. Bean wrote:
Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?

Does one use ordinary masonry drills?

Any undertakers out there?

A quick Google search on "drill marble slab" came up with hits to
support my first idea for drilling the marble: use a copper tube
the diameter of the hole you want, in a drill press at _low_ speed,
with lots of (fairly coarse) abrasive powder, lots of water, and low
pressure on the drill bit. It's the same rig I use for drilling glass.

You will want a stream of running water so that the bit is kept cool
and lubricated, and the abrasive doesn't turn into a hard paste.
It will be messy; if you can put the slab in a cookie tin or
aluminum-foil pan, and run the excess out through a tube, that will
help. You also could build a modeling-clay dam around the hole.

It's almost impossible to over-lubricate, but it's really easy to
under-lubricate.

See http://www.shopsmartxpress.com/Ameri...lt.htm?M9a.htm
for some useful tips.

Polishing is easy: coarse-to-fine sandpaper, then buff with increasingly
fine powdered abrasive, up through white rouge or so. You have to get
all the old abrasive out of the polishing tool before you put the new,
finer abrasive in -- but you knew that.

Marble is rather soft, though quite abrasive, and so it's easy to
take off more than is necessary.

--
Mike Andrews

Tired old sysadmin

"Airy R. Bean" wrote in message ...
Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?

Does one use ordinary masonry drills?

Any undertakers out there?

If you will stop by any trophy shop you can get all sorts of marble
,color,shape size etc. quite reasonable too. may already have holes
that you can use. Harold W4PQW

"Airy R. Bean" wrote in message
...
Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?

Does one use ordinary masonry drills?

Any undertakers out there?


An ordinary masonry drill is perfect.It goes through it like cheese. The
material is basically quite soft and can be easily shaped with an angle
grinder and a cheap diamond cutting disc (those for cutting bricks, flags
etc) . For final levelling use various grades of car 'wet-n-dry' (Silicon
Carbide paper) and finish using Silicon Carbide (or even diamond!) 'lapping
paste' slurries.
(nb. for rust stains soak in oxalic acid)
regards
john

Good idea!

wrote in message
om...
"Airy R. Bean" wrote in message
...
Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?
Does one use ordinary masonry drills?
Any undertakers out there?

If you will stop by any trophy shop you can get all sorts of marble
,color,shape size etc. quite reasonable too. may already have holes
that you can use. Harold W4PQW

OK - I'll try that out on some off-cuts, assuming that such
things are available.

Otherwise - I'm collecting various bits of metal to make up a
bug key but am distracted by vertical antenna and its ATU.

I am trying to conceive of a minimal switching scheme to accommodate
the 10 ATU configurations discovered so far....
Straight through
Series C
Series L
Series C-L
"L" network with C on TX side
"L" network with C on ant side
"PI" network
"T" network
Parallel tank, series fed
Parallel tank, parallel fed

"john jardine" wrote in message
...
"Airy R. Bean" wrote in message
...
Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?
Does one use ordinary masonry drills?
Any undertakers out there?
An ordinary masonry drill is perfect.It goes through it like cheese. The
material is basically quite soft and can be easily shaped with an angle
grinder and a cheap diamond cutting disc (those for cutting bricks, flags
etc) . For final levelling use various grades of car 'wet-n-dry'
(Silicon
Carbide paper) and finish using Silicon Carbide (or even diamond!)
'lapping
paste' slurries.
(nb. for rust stains soak in oxalic acid)
regards
john

Presumably also, therefore, with the miniature grinding
wheels of the "Dremel" style?

"john jardine" wrote in message
...material is basically quite soft and can be easily shaped with an angle
grinder....

In article ,
"Airy R. Bean" wrote:

Good idea!

wrote in message
om...
"Airy R. Bean" wrote in message
...
Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?
Does one use ordinary masonry drills?
Any undertakers out there?

If you will stop by any trophy shop you can get all sorts of marble
,color,shape size etc. quite reasonable too. may already have holes
that you can use. Harold W4PQW



I get my used marble from our town's recycling center. You'd be
surprised how many "trophies" are thrown out. I find the side I want and
disassemble it. I even use them for heat blocks when I am doing some
heavy duty soldering. If they crack, I toss them. And...the price is
right!

Al

Assuming that one could obtain a slab of marble for the
base of a home grown bug key, is it an easy thing to
polish and to drill?

Does one use ordinary masonry drills?

Any undertakers out there?
==============================
Yes that will do . I drilled a slate base (similar to marble ) for a pump
key .
It might be helpful to drill with the marble immersed in water.
This method also enables drilling in glass , for example to fit a
feed-through for an antenna (single glazing of course)

Frank GM0CSZ / KN6WH

I'll make up some switches out of brass rod - what I
have in mind is something like a large banana plug & socket
combination activated by nylon or PTFE rods. (I don't envisage
one FG rotary switch - I'll do it with separate switches,
possibly with some interlocking along the lines of
old railway signal box practice - I've enough books here
on that subject!

Primary doodles indicate that the antenna could be left
permanently connected to the inductor and one of the C's,
except in the case of a "T" network when it needs to be
connected to the other end of the said C.

There won't be any relays. The vertical antenna to the base
of which the ATU will be directly coupled is about 10 ft from
the shack and what I have in mind to use is a series of
activating rods - cunningly hidden/faced by a small picket fence.

The only area of development I haven't yet sussed out is how
to pass the operating rods into and out of a sealed (to keep
out the rain) chamber. Perhaps something like the stern
gland of a ship's propeller shaft might come into play here.

"john jardine" wrote in message
...
The 'select 1 of 10' ATU would seem a grade 1 mechanical-electrical
juggernaut of switches, relays?, screening cans, adjustable inductors
(roller coasters?), variables caps, connectors and knobs. I wish you a
interesting journey :-).

PS. Don't expect any reports of rapid progress - mechanical
contrivances seem to take me an age, and I'm also undertaking
my own "vibroplex" bug key at the same time (Hence this
thread about marble slabs) . Mechanics is frustratingly slow.....

1. In software, you get an idea, and a couple of hours later, your
prototype is working well and exciting you as to the possibilities
of the next version.

2. In hardware, you get an idea, and a couple of days later, your
prototype breadboard is singing along.

3. In mechanics, you get an idea which requires 10 components,
and one week later you're lucky if you've managed to make the jig
for machining the first of those components!

"Airy R. Bean" wrote in message
...
I'll make up some switches out of brass rod -

"Airy R. Bean" wrote in message
...
PS. Don't expect any reports of rapid progress - mechanical
contrivances seem to take me an age, and I'm also undertaking
my own "vibroplex" bug key at the same time (Hence this
thread about marble slabs) . Mechanics is frustratingly slow.....

1. In software, you get an idea, and a couple of hours later, your
prototype is working well and exciting you as to the possibilities
of the next version.

You didn't manage that at Westinghouse, did you? As I recall you got sacked
for not getting it working.

2. In hardware, you get an idea, and a couple of days later, your
prototype breadboard is singing along.

With or without Big K?

3. In mechanics, you get an idea which requires 10 components,
and one week later you're lucky if you've managed to make the jig
for machining the first of those components!


Fettled castings, stuck threads, etc etc.

"Airy R. Bean" wrote in message
...
Presumably also, therefore, with the miniature grinding
wheels of the "Dremel" style?

"john jardine" wrote in message
...material is basically quite soft and can be easily shaped with an
angle
grinder....



Yes. They work very well (even more so the diamond tipped fitments) but
take a god awful amount of time to process any useful areas.

The 'select 1 of 10' ATU would seem a grade 1 mechanical-electrical
juggernaut of switches, relays?, screening cans, adjustable inductors
(roller coasters?), variables caps, connectors and knobs. I wish you a
interesting journey :-).
During a radio phase I think I also tried 'em all. Concluded they're all
much-of-a-muchness and finally settled on a 2 component "L". (The human
ear's 'Db' response seems to make a bit of a mockery of equipment technical
spec's :-).
regards
john

"Airy R. Bean" wrote in message
...
PS. Don't expect any reports of rapid progress - mechanical
contrivances seem to take me an age, and I'm also undertaking
my own "vibroplex" bug key at the same time (Hence this
thread about marble slabs) . Mechanics is frustratingly slow.....

1. In software, you get an idea, and a couple of hours later, your
prototype is working well and exciting you as to the possibilities
of the next version.

2. In hardware, you get an idea, and a couple of days later, your
prototype breadboard is singing along.

3. In mechanics, you get an idea which requires 10 components,
and one week later you're lucky if you've managed to make the jig
for machining the first of those components!

"Airy R. Bean" wrote in message
...
I'll make up some switches out of brass rod -


Absolutely true!.
About 30 years ago I picked up a rake of bits and pieces from an amateur who
operated in the 30's. Drawers full of brass stud terminals, connectors, wire
crimp ends, knob pointers etc. nickel plated screw-downs etc. They're much
too nice to use for normal construction and I've been waiting for a project
to turn up where it's worth spending the time to make use of them. (maybe
have to invent some kind of art-deco project) The Vibroplex idea is just
this kind of much-sweat-n-toil, 'object of beauty', that's actually worth
passing down from generation to generation. All the electronics and
programming I've ever done, is so GD transient that I'm lucky to remember
any of it after even a couple of years.
regards
john

A fatal attitude to progressing with useful projects in
the mean time!

I had this approach to a number of things until someone
pointed out to me that the most expensive and luxurious
item that is already in your junk box is much, much
cheaper than the shoddiest thing you can buy!

Now, if it's to hand, and will do the job, I use
it and move on.

For example, I had a 28MHz 2-ele beam that was in
its original packing for many years - then the aluminiium
tube got used to make the legs of a clock-testing horse
last year.


"john jardine" wrote in message
...
...... They're much
too nice to use for normal construction and I've been waiting for a
project
to turn up where it's worth spending the time to make use of them......

I forgot the SPC, but that appears to need a differential
capacitor that I haven't yet obtained (or made).

Also, ISTR reading somewhere (that I cannot find) that
the SPC arrangement is very lossy, and can result in
3/4 of the power being lost in the ATU itself)

For the other configurations below, I've worked out that I
need only 8 simple on-off switches to effect all the configurations
below, including the safety issue of isolating the antenna from the
TX and earthing it.

"Airy R. Bean" wrote in message
...
I am trying to conceive of a minimal switching scheme to accommodate
the 10 ATU configurations discovered so far....
Straight through
Series C
Series L
Series C-L
"L" network with C on TX side
"L" network with C on ant side
"PI" network
"T" network
Parallel tank, series fed
Parallel tank, parallel fed

In article , Airy R. Bean wrote:

I forgot the SPC, but that appears to need a differential
capacitor that I haven't yet obtained (or made).

The SPC circuits I've seen (including the classic design in the late
'90s ARRL Handbook) does not use a differential capacitor. Its output
capacitor is a dual-section non-differential type - the two sections
track in parallel.

I have seen some T-type tuners which use a differential capacitor,
with one section being the input cap and the other being the output
cap. MFJ sells one of these. These are advertised as being more
convenient, since establishing a match requires tuning only two
controls rather than three. However, I doubt that this arrangement
results in the most efficient match.

Also, ISTR reading somewhere (that I cannot find) that
the SPC arrangement is very lossy, and can result in
3/4 of the power being lost in the ATU itself)

I don't think that's a specific characteristic of the SPC - it seems
to be true of T tuners in general. The T configuration does provide a
wide matching range, but in the case of very low-impedance or highly
reactive loads the "match" may result in extremely high circulating
currents through the coil, with the resulting high losses. A "T"
tuner with sufficient reactance in the components may let you
establish a "match" for a short-circuited load... but you'll end up
dissipating almost 100% of your power in the coil. The SPC probably
shares the same characteristic.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Thanks - that explains it nicely.

"Dave Platt" wrote in message
...
In article , Airy R. Bean
wrote:
I forgot the SPC, but that appears to need a differential
capacitor that I haven't yet obtained (or made).
I don't think that's a specific characteristic of the SPC - it seems
to be true of T tuners in general. The T configuration does provide a
wide matching range, but in the case of very low-impedance or highly
reactive loads the "match" may result in extremely high circulating
currents through the coil, with the resulting high losses. A "T"
tuner with sufficient reactance in the components may let you
establish a "match" for a short-circuited load... but you'll end up
dissipating almost 100% of your power in the coil. The SPC probably
shares the same characteristic.