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sorting out grinder/polisher options



 
 
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  #1  
Old June 14th 09, 10:05 AM posted to rec.crafts.jewelry
sorrentoSilver
external usenet poster
 
Posts: 1
Default sorting out grinder/polisher options

hello rcj:

I'm in the market for a grinder for my silverwork bench and trying to
sort out the various options and what's important. I only want to use
it to grind/edge/reduce silver and for some occasional tool
shaping . . . but NOT for polishing - I love using my lortone tumbler
for what I do. so I know I don't need the felt and muslin buffing
wheels. I was thinking if I had two spindles, I'd have a fine and
coarser wheel option . . . the traditionalists in the group will be
pleased to learn that I LOVE to use my files too - this is where the
hand, heart, and soul interact for me in silver work. I just want the
grinder for quick and easy shaping of larger pieces - say to smooth
and straighten the edge of a bangle I've just cut out, etc.


so, I'm trying to learn about the differences between the $35 units
one can buy at home depot or online everyhwere and the ones the
jewelry supply houses sell. is variable speed important? is the
overall HP an important issue? how much power will I need to grind
silver sheet?

must I have a hood and fan and all that stuff? I don't want to try to
make my own if I must have one - so that would force me to a more
expensive unit, I think.

what's the importance of size of the wheels? does 6" vs 3" matter?

where/how can I learn about spindles and arbors and that side of the
story?

contenti has an inexpensive model with a flexshaft attached. is this
a mistake? any good for what I need? is it possible to buy a hardware
store grinder and get a hood for it if that's important?

I already have a foredom which I do pre-finishing work on with the 3m
radial brushes and rubberized abrasives - but it wouldn't hurt to have
an extra handpiece available.

I thank you in advance for any help/advice/information you can share
with me.
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  #2  
Old June 15th 09, 03:32 AM posted to rec.crafts.jewelry
Peter W. Rowe[_2_]
external usenet poster
 
Posts: 115
Default sorting out grinder/polisher options

On Sun, 14 Jun 2009 02:05:19 -0700, in rec.crafts.jewelry sorrentoSilver
wrote:

hello rcj:

I'm in the market for a grinder for my silverwork bench and trying to
sort out the various options and what's important. I only want to use
it to grind/edge/reduce silver and for some occasional tool
shaping . . . but NOT for polishing - I love using my lortone tumbler
for what I do. so I know I don't need the felt and muslin buffing
wheels. I was thinking if I had two spindles, I'd have a fine and
coarser wheel option . . . the traditionalists in the group will be
pleased to learn that I LOVE to use my files too - this is where the
hand, heart, and soul interact for me in silver work. I just want the
grinder for quick and easy shaping of larger pieces - say to smooth
and straighten the edge of a bangle I've just cut out, etc.


First. lets be sure we're talking about the correct machines and terms.
"grinders" usually refers to bench mounted motors, usually without any dust
collection or filtering means, with literally a grinding wheel, usually a fine
and coarse one on a side, PERMENANTLY mounted to each side, rotating within a
fitted protective shield. These most commonly are used for grinding and
sharpening, often with wheels optimized for things like steel.

Polishing machines, however, while there is a similar motor, have tapered
spindles on one or both sides, to allow the use of buffs, various other wheels
with a soft center that can screw onto the tapered thread. These often have
hoods behind the spindles fitted with dust collection means, normally a fan
pulling air through a filter from behind the wheel.

The reason I mention this is that machines normally sold as grinders are not
meant for, or suited for, polishing in most cases, simply because they're not
meant for wheels to be commonly interchanged or removed.

The two types of machine, while similar in the sense both have a motor, differ
in their intended use by quite a bit. There are also small multipurpose units,
some with a grinding wheel or a tapered spindle (multipurpose) on one side and a
flex shaft on the other. Generally less capable in any role than the larger
more dedicated machines, but at their lower capabilities, they can fill more
roles.



so, I'm trying to learn about the differences between the $35 units
one can buy at home depot or online everyhwere and the ones the
jewelry supply houses sell.


The "sold everywhere" versions are grinders. Good for sharpening chisels and
drill bits. Will also grind silver, but it's not their intended use, and the
results may not be quite what you hope. On soft metals like silver, these
machines tend to leave very rough edges, and the wheels tend to clog up quickly.
They're intended for steel.

The jewelry supplier machines, by contrast, usually are intended for polishing
metal. That means buffs of various types. You can get grinding wheels that can
mount on these, but grinding, rather than polishing, is not their intended use.

is variable speed important?


For a grinding wheel, most often there is an optimum speed. Going slower can
help to avoid burning/overheating of metal, especially steels, where it messes
up the heat treatment and hardening, if any. Most grinders run at 3450 rpm. For
polishing, again, most full size/professional machines run also at 3450 rpm.
Some are dual speed, also allowing the slower 1725, which can be nice for some
uses, and some types of wheels, notably some texturing wheels and brushes, which
work better slower. the smallest of the polishing motors, the fordom bench type
and a few others, may offer variable speed. Sometimes this might be useful, but
most of the time, for straight buffing purposes, it's not needed.

is the
overall HP an important issue? how much power will I need to grind
silver sheet?


Power relates to how big a wheel you can run with a full load. More is better,
but not necessarily always needed. Most full size polishing machines usually
need at least 1/4 hp or so, maybe slightly less for light duty versions. A
bigger motor won't slow down when you bear into it with a larger buff. But
you're talking about grinding, which may present less of a load to the wheel, so
larger hp may not be needed.


must I have a hood and fan and all that stuff? I don't want to try to
make my own if I must have one - so that would force me to a more
expensive unit, I think.


For grinding, probably not. Grinding dust tends to be coarse, and doesn't fly
into the air. Dust collection means helps you to prevent what does get into the
air from getting into your lungs, and helps to recover precious metals if that's
what you're grinding. Polishing machines, on the other hand, are more in need
of dust control of some sort. Polishing compounds often are very fine powders,
sometimes things like silicates, not good to breath, and also the dust thrown
off the felt or muslin wheels. This stuff gets into the air, all over
everything, and you don't want it in your lungs either. In both cases, of you
are on a budget, you can take care of the safety issues with a good dust mask.
the mess from a buffing machine, well, suit yourself. But most people prefer
some sort of collection means, and with the cost of precious metals, it
eventually pays for itself, even with silver.


what's the importance of size of the wheels? does 6" vs 3" matter?


Yeah. at the same rpm, the six inch wheel cuts more than twice as fast. Larger
wheels mean a higher surface speed, so faster grinding. And they last longer.
But both do the job. It's question of how fast.


where/how can I learn about spindles and arbors and that side of the
story?


Again, the main thing is to understand that you seem to be lumping together two
distinctly different types of equipment. Grinders use wheels that are not
intended to be changed back and forth, so their bolted to the arbors, removed
only when the wheel is worn and needs changing. Polishing motors, on the other
hand intend to allow you to work with many different types of buffs and wheels,
so the tapered threaded spindles make that possible. The motors can also be
fitted with fixed arbors that mount a wheel the same as a grinding wheel, but
this is not their most common use. Tapered spindles require that the center
hole of the wheel is soft, and generally small enough to "jam" on the spindle.
Many are sold with only a small hole to start, which ends up widening up as it's
used. Wheels intended for fixed mounting usually have a uniform center arbor
hole, often 1/2 inch or some similar size, that get mounted between flanges and
secured with a nut on the threaded shaft of the arbor.


contenti has an inexpensive model with a flexshaft attached. is this
a mistake? any good for what I need? is it possible to buy a hardware
store grinder and get a hood for it if that's important?

I already have a foredom which I do pre-finishing work on with the 3m
radial brushes and rubberized abrasives - but it wouldn't hurt to have
an extra handpiece available.

I thank you in advance for any help/advice/information you can share
with me.



With all the above said and done, I'd like to digress with another suggestion.
If what you wish to do is to literally grind silver edges, with no intent to
polish the metal, then I'd suggest that you're actually looking at the wrong
type of machine. Bench grinders are rather harsh for what you wish, and the
wheels tend to clog up when used with soft metals. They'd do the job, but I
think they're not the best.

Rather, I'd suggest you look at small bench mounted sanding belt machines.
Dremel makes one, and there are others. These use an easily replaced belt of
sanding cloth, running over a couple vertically mounted pulleys. Usually there
is a table with a fixed support behind the belt to let you rest the sheet metal
or whatever on the table to feed into the belt, and if you need to work on
curves, the upper part of the belt is unsupported, and can conform to a curve.
I've seen machines like this for not much more than the cheap grinders, and you
can get a wide range of grits and abrasive belts for these. The types of
abrasives used will be more resistant to clogging, and may cut faster for this
than a grinding wheel, though you'll have to replace the belts as they get worn
(they're cheap). Some of the machines are made with a disk sander on one side
too, which can also be useful especially if you wish to get a straight edge on
something.

For the specific use you're describing, I'd guess that these small bench mounted
belt sanders are a better choice than either a bench grinder or a polishing
machine, which is what you'd been describing.

There are a number of brands and prices of these units. Most will do the job
just fine. Here's a cheap one from Harbor Freight:

http://www.harborfreight.com/cpi/cta...temnumber=2485

My suggestion, for the specific task you describe, of removing metal from the
edges of sheet metal, would be one of these machines. They work well, faster
and easier to control than a normal bench grinder for this use. And, because
the motor is below the level of where you're working, it doesn't get in the way
with larger pieces of sheet or stock. And you can do almost any of the normal
grinding tasks you might normally do on a bench grinder as well. But again,
each tool has those tasks for which it's best. Sharpening and shaping steel
tools, gravers, drill bits, etc, is easier on the rigid fixed wheels of a bench
grinder. Free form trimming of sheet metal edges is often easier on the belt
sander. And for actual polishing or refining a surface or an edge, you need a
polishing wheel or buff, which generally means that type of machine...

Peter Rowe
  #3  
Old June 20th 09, 05:40 PM posted to rec.crafts.jewelry
Mouse
external usenet poster
 
Posts: 2
Default sorting out grinder/polisher options

Peter W. Rowe wrote:
On Sun, 14 Jun 2009 02:05:19 -0700, in rec.crafts.jewelry sorrentoSilver
wrote:

hello rcj:

I'm in the market for a grinder for my silverwork bench and trying to
sort out the various options and what's important. I only want to use
it to grind/edge/reduce silver and for some occasional tool
shaping . . . but NOT for polishing - I love using my lortone tumbler
for what I do. so I know I don't need the felt and muslin buffing
wheels. I was thinking if I had two spindles, I'd have a fine and
coarser wheel option . . . the traditionalists in the group will be
pleased to learn that I LOVE to use my files too - this is where the
hand, heart, and soul interact for me in silver work. I just want the
grinder for quick and easy shaping of larger pieces - say to smooth
and straighten the edge of a bangle I've just cut out, etc.


First. lets be sure we're talking about the correct machines and terms.
"grinders" usually refers to bench mounted motors, usually without any dust
collection or filtering means, with literally a grinding wheel, usually a fine
and coarse one on a side, PERMENANTLY mounted to each side, rotating within a
fitted protective shield. These most commonly are used for grinding and
sharpening, often with wheels optimized for things like steel.

Polishing machines, however, while there is a similar motor, have tapered
spindles on one or both sides, to allow the use of buffs, various other wheels
with a soft center that can screw onto the tapered thread. These often have
hoods behind the spindles fitted with dust collection means, normally a fan
pulling air through a filter from behind the wheel.

The reason I mention this is that machines normally sold as grinders are not
meant for, or suited for, polishing in most cases, simply because they're not
meant for wheels to be commonly interchanged or removed.

The two types of machine, while similar in the sense both have a motor, differ
in their intended use by quite a bit. There are also small multipurpose units,
some with a grinding wheel or a tapered spindle (multipurpose) on one side and a
flex shaft on the other. Generally less capable in any role than the larger
more dedicated machines, but at their lower capabilities, they can fill more
roles.


so, I'm trying to learn about the differences between the $35 units
one can buy at home depot or online everyhwere and the ones the
jewelry supply houses sell.


The "sold everywhere" versions are grinders. Good for sharpening chisels and
drill bits. Will also grind silver, but it's not their intended use, and the
results may not be quite what you hope. On soft metals like silver, these
machines tend to leave very rough edges, and the wheels tend to clog up quickly.
They're intended for steel.

The jewelry supplier machines, by contrast, usually are intended for polishing
metal. That means buffs of various types. You can get grinding wheels that can
mount on these, but grinding, rather than polishing, is not their intended use.

is variable speed important?


For a grinding wheel, most often there is an optimum speed. Going slower can
help to avoid burning/overheating of metal, especially steels, where it messes
up the heat treatment and hardening, if any. Most grinders run at 3450 rpm. For
polishing, again, most full size/professional machines run also at 3450 rpm.
Some are dual speed, also allowing the slower 1725, which can be nice for some
uses, and some types of wheels, notably some texturing wheels and brushes, which
work better slower. the smallest of the polishing motors, the fordom bench type
and a few others, may offer variable speed. Sometimes this might be useful, but
most of the time, for straight buffing purposes, it's not needed.

is the
overall HP an important issue? how much power will I need to grind
silver sheet?


Power relates to how big a wheel you can run with a full load. More is better,
but not necessarily always needed. Most full size polishing machines usually
need at least 1/4 hp or so, maybe slightly less for light duty versions. A
bigger motor won't slow down when you bear into it with a larger buff. But
you're talking about grinding, which may present less of a load to the wheel, so
larger hp may not be needed.

must I have a hood and fan and all that stuff? I don't want to try to
make my own if I must have one - so that would force me to a more
expensive unit, I think.


For grinding, probably not. Grinding dust tends to be coarse, and doesn't fly
into the air. Dust collection means helps you to prevent what does get into the
air from getting into your lungs, and helps to recover precious metals if that's
what you're grinding. Polishing machines, on the other hand, are more in need
of dust control of some sort. Polishing compounds often are very fine powders,
sometimes things like silicates, not good to breath, and also the dust thrown
off the felt or muslin wheels. This stuff gets into the air, all over
everything, and you don't want it in your lungs either. In both cases, of you
are on a budget, you can take care of the safety issues with a good dust mask.
the mess from a buffing machine, well, suit yourself. But most people prefer
some sort of collection means, and with the cost of precious metals, it
eventually pays for itself, even with silver.


what's the importance of size of the wheels? does 6" vs 3" matter?


Yeah. at the same rpm, the six inch wheel cuts more than twice as fast. Larger
wheels mean a higher surface speed, so faster grinding. And they last longer.
But both do the job. It's question of how fast.

where/how can I learn about spindles and arbors and that side of the
story?


Again, the main thing is to understand that you seem to be lumping together two
distinctly different types of equipment. Grinders use wheels that are not
intended to be changed back and forth, so their bolted to the arbors, removed
only when the wheel is worn and needs changing. Polishing motors, on the other
hand intend to allow you to work with many different types of buffs and wheels,
so the tapered threaded spindles make that possible. The motors can also be
fitted with fixed arbors that mount a wheel the same as a grinding wheel, but
this is not their most common use. Tapered spindles require that the center
hole of the wheel is soft, and generally small enough to "jam" on the spindle.
Many are sold with only a small hole to start, which ends up widening up as it's
used. Wheels intended for fixed mounting usually have a uniform center arbor
hole, often 1/2 inch or some similar size, that get mounted between flanges and
secured with a nut on the threaded shaft of the arbor.

contenti has an inexpensive model with a flexshaft attached. is this
a mistake? any good for what I need? is it possible to buy a hardware
store grinder and get a hood for it if that's important?

I already have a foredom which I do pre-finishing work on with the 3m
radial brushes and rubberized abrasives - but it wouldn't hurt to have
an extra handpiece available.

I thank you in advance for any help/advice/information you can share
with me.



With all the above said and done, I'd like to digress with another suggestion.
If what you wish to do is to literally grind silver edges, with no intent to
polish the metal, then I'd suggest that you're actually looking at the wrong
type of machine. Bench grinders are rather harsh for what you wish, and the
wheels tend to clog up when used with soft metals. They'd do the job, but I
think they're not the best.

Rather, I'd suggest you look at small bench mounted sanding belt machines.
Dremel makes one, and there are others. These use an easily replaced belt of
sanding cloth, running over a couple vertically mounted pulleys. Usually there
is a table with a fixed support behind the belt to let you rest the sheet metal
or whatever on the table to feed into the belt, and if you need to work on
curves, the upper part of the belt is unsupported, and can conform to a curve.
I've seen machines like this for not much more than the cheap grinders, and you
can get a wide range of grits and abrasive belts for these. The types of
abrasives used will be more resistant to clogging, and may cut faster for this
than a grinding wheel, though you'll have to replace the belts as they get worn
(they're cheap). Some of the machines are made with a disk sander on one side
too, which can also be useful especially if you wish to get a straight edge on
something.

For the specific use you're describing, I'd guess that these small bench mounted
belt sanders are a better choice than either a bench grinder or a polishing
machine, which is what you'd been describing.

There are a number of brands and prices of these units. Most will do the job
just fine. Here's a cheap one from Harbor Freight:

http://www.harborfreight.com/cpi/cta...temnumber=2485

My suggestion, for the specific task you describe, of removing metal from the
edges of sheet metal, would be one of these machines. They work well, faster
and easier to control than a normal bench grinder for this use. And, because
the motor is below the level of where you're working, it doesn't get in the way
with larger pieces of sheet or stock. And you can do almost any of the normal
grinding tasks you might normally do on a bench grinder as well. But again,
each tool has those tasks for which it's best. Sharpening and shaping steel
tools, gravers, drill bits, etc, is easier on the rigid fixed wheels of a bench
grinder. Free form trimming of sheet metal edges is often easier on the belt
sander. And for actual polishing or refining a surface or an edge, you need a
polishing wheel or buff, which generally means that type of machine...

Peter Rowe

I use a 4" belt sander and also a 1" belt sander all the time for
shaping and rounding the edges of sheet silver that I've cut out. Peter
is right about the usefulness of the belt sander over a grinder. I
bought my 1" model from Enco for about $80 and it works just fine for my
needs. A grinder wheel is unforgiving and sharp-edged and often
constructed in such a way that the motor gets in the way of the work.
The Zirconia Alumina belts last much longer than the Aluminum Oxide and
are available from, among other places, www.customsandingbelts.com
 




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