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[Neural]

I know some of you probably work with metal on a larger scale than jewelry.

I've got a project that is a new medium for me.  I want to create a special gift for my mother for her 75th birthday in September, and I've chosen to do what is known as "ground metal art".

Simply: using grinding discs or brushes, patterns are created in sheet metal, usually aluminum, and then colored with various types of transparent paint to bring about some really pretty results.

I'm a bit limited on what I can do right now, and the only tool I have relative to the work is a drill.  The problem I have come across is that the angle at which the wheel spins compared to how you hold the drill makes sweeping arcs and such more difficult to do smoothly (after watching many videos, I now understand why most of the artists use angle grinders).

So, my questions are as follows:

Most of the stuff I have seen, it appears that the work is being done with angle grinders that have had the safety guard removed, which makes sense due to the fact that the tool is being used in a manner that the guard would hinder, but that sort of makes the whole thing less safe (hence the name safety guard).  Others have used angle die grinders, which appear to be the same thing, only they appear to only be available in pneumatic form, and the shaft that holds the wheel appears to be longer by about an inch or so.   Is the safety guard on an standard angle grinder there primarily to protect your fingers due to the close proximity of the wheel itself?  Is there some sort of guard on a die grinder that they are also removing?

Other questions:
Since the objective is to scratch metal more than grind things away, can I get away with a lower amperage (and therefore cheaper) grinder? (I can't do anything requiring an air compressor at this time).
Any brand suggestions?
and last but not least, does anyone have some flexible 80+ grit discs they are no longer in need of that they are willing to part with cheap?

Thanks. :D

[Slabbercabber]

The main purpose of the guard is to protect fingers.  Most angle grinders have far more power than you will need for what you propose unless you want to use a wire brush.  Those use more power.  There are also flap discs used for sanding.  As an  aside, if you look at any professional welders' grinders you will find that the guards are always removed as they wear gloves and the guards just get in the way.

[mirkaba]

I bought a really nice Makita angle grinder at a garage sale for 20.00. The safety guard was already gone. Always some on Ebay. I bought a new Chinese one a few years back and it actually burst into flames after a half hour or so of hard use. I have done disc patterns with the Foredom. It is always a good idea to practice on some scrap before you go for it. Good Luck.........Bob

[Neural]

The main purpose of the guard is to protect fingers.  Most angle grinders have far more power than you will need for what you propose unless you want to use a wire brush.  Those use more power.  There are also flap discs used for sanding.  As an  aside, if you look at any professional welders' grinders you will find that the guards are always removed as they wear gloves and the guards just get in the way.

I suspected that was the case.   It's rare that I use a hand power tool when building things or such that I'm not wearing leather gloves, so that makes sense.  The discs I'm intending to use are the flexible kind.  Aluminum is pretty easy to scratch, and getting a given effect out of it is pretty easy, so heavy duty grinding discs are just making more work than necessary.   

I'll post pics at some point.  Right now I'm just doodling and seeing what can be done. :D

Mirkaba: I purchased a piece of 2' x 2' sheet purely for practice.  What's nice about working with sheet metal, is it has two sides.  2x the practice space :D

[edgarscale]

for small things like disks could you not use a Fordom while your disk is held in place with wax so the piece don't move unnecessarily?

[Phishisgroovin]

The main purpose of the guard is to protect fingers.  Most angle grinders have far more power than you will need for what you propose unless you want to use a wire brush.  Those use more power.  There are also flap discs used for sanding.  As an  aside, if you look at any professional welders' grinders you will find that the guards are always removed as they wear gloves and the guards just get in the way.

incorrect, the main reason for the shield is to deflect a grinding wheel from lodging itself inside your head or other body parts if it cracks and breaks away from the grinder.

[Neural]

The main purpose of the guard is to protect fingers.  Most angle grinders have far more power than you will need for what you propose unless you want to use a wire brush.  Those use more power.  There are also flap discs used for sanding.  As an  aside, if you look at any professional welders' grinders you will find that the guards are always removed as they wear gloves and the guards just get in the way.

incorrect, the main reason for the shield is to deflect a grinding wheel from lodging itself inside your head or other body parts if it cracks and breaks away from the grinder.

Gotta agree there.  I had a long discussion with the manufacturer of the wheels I'm using, as they are basically a sponge material (can squish them slightly with finger pressure).  I asked specifically about whether or not they would shatter.  His statement was that they've never in all the years of production seen one do such a thing.  Doesn't mean it can't happen, but the structure of the material is more something that would tear, than break (again, it's basically a denser version of a kitchen sponge).    They are rated for 13k rpm, and the grinder only goes 11k, so there is some margin of safety there. 
My concern, even with the guard on, is that there's an area that is *not* guarded, and I need to know if someone standing near by might also be in danger, and the basic answer was "no".

All that said, my plans hit a major snag, and I have had to put the whole project on hold.  I have to work outside, and the sun plus 115F heat resulted in the grinding wheel burning, leaving black marks in the aluminum.  That and it's a miracle the grinder itself didn't burn out.  It was hot on my hand through the gloves.  So.. I have to wait until fall. :/