You might find it easiest to use a small ball bur and flexshaft for
material removal, Andrew. A bur size somewhere around a 010 to a 015
would be a good place to start. It works pretty well and is a whole
lot easier to do than using flat bottom gravers. The finish is a bit
different, but it's not at all unattractive, especially as a base for
translucent enamels. With some experimentation, you'll probably come
up with several different finishes. It would probably be best if you
cut the outline with a square graver before removing the material to
provide a clean, crisp edge to cut to. Otherwise, your edges can be a
little ragged and undefined. With a little practice using a small bur
though, you can make a pretty clean edge that is quite suitable for
Technique for bulk removal is called wriggling.
Wriggle is one of many time-honored engraver's short cuts. But as a
technique for bulk material removal it is wholly unsuitable. Its
intended use is quite the opposite, in fact.
Wriggle is an engraving technique used for making decorative wide
lines quickly and is traditionally seen in block or Old English style
lettering where wide, long lines are needed without putting a ton of
time into the job. In modern times it is used quite extensively in
Western style scroll work, such as that seen on belt buckles and
Wriggle is done with a flat bottom graver or sometimes a liner. The
design line is used as the center of the wide line, and small
triangular cuts are made in sort of a "tic-tac" style by alternately
rolling the graver left and right on either side of the center. The
rule of thumb is that each cut should be approximately half as long
as the graver is wide so that each pair of left and right cuts
approximately equals the width of the graver, thus forming
equilateral triangle shaped bright cuts and removing little or
ideally no material from the center of the line. Its main use is to
cover lots of area quickly *without* removing much material.
This is not a joke! You must have first aid kit on hand while
learning wriggling and be prepared to cope with large bleedings.
Any time such a warning is given, the technique described should be
taken with a healthy dose of skepticism. Using wriggle as a method of
material removal can most definitely be a dangerous thing to try,
especially with hand gravers. If you do try it, then do as Leonid
suggests. Keep a first aid kit handy. You're probably going to need
it. Keep your sharpening tools close by too, you're going to need
them a lot as well.
The proper technique for using gravers for material removal is
covered in the book "The Art of Engraving" by James B. Meek in the
section on making inlays. In short, the outline of the area is
engraved with a square graver, then a flat bottom graver is used in
multiple passes to remove material from within the outline. The flat
bottom should have a small heel, or as I use mine, a slight radius. I
use about 5 to 7 degrees of radiused heel and around 55 degrees on
the face. The reason for the heel is to allow the handle to be raised
slightly, otherwise the engraver's knuckles can interfere with the
cutting. I would recommend starting with a number 42 graver or
smaller with a flat bottomed mushroom handle to give your knuckles
even more clearance. The wider the graver, the harder it is to do.
In the "old days", material removal with gravers usually involved
"hammer and chisel" tools and technique. Nowadays, most of us use
standard flat bottoms and air power. It can be done with hand gravers
and no power, but it takes a lot of time and effort to muscle your
way through. Even the sharpest flat bottom graver used with the
slickest lubricants will not "glide" through the metal, it must be
forced through. Multiple extremely shallow cuts are much more easily
(and safely) accomplished than trying to carve out large chunks of
metal in a single pass. This is one of the very few cases in which
making multiple passes over the same lines is considered acceptable
practice in engraving.
In any event, if you are doing it in a manner that puts your hands
at risk as Leonid describes, you aren't doing it right and you will
probably end up making a real mess of the piece in addition to
bleeding all over it. All that slipping causes a lot of unplanned and
unwanted cutting of the work as well as body parts. Gravers don't
come with erasers so if you put an unwanted cut somewhere, most of
the time all you can do is to try to somehow incorporate the slip
into the design.
Try the ball bur technique first. It's comparatively very easy to do
and puts your hands and your work at minimal risk of damage. You
might try it out on a piece of scrap first, just to get the feel.
Don't try to hog it all out on one pass; try several crossing passes,
each removing a little more depth. The only real risk is having the
bur catch an edge or something and spinning out of control which
usually cuts a jagged little trough with a round hole at the end of
wherever it ends up going. That can be as hard to deal with as a
graver slip, so try to avoid it!
Hope you find this helpful!