Fly Cutters

I want to machine a thin piece of stainless sheet(and some fiberglass too) for an instrument panel. I am not happy with the results I'm
getting with an endmill, and want(or think I need) to get a flycutter.
Looking at the usual MSC/Enco/McMaster, I see two basic variations. I see "Rip Flycutters" and "Fly tool cutters". Other variations include the "roughing and finishing fly tool system", etc.
From what I can tell, the rip flycutters can take a 1/2" bit, which would work nicely with my existing indexable holders. The rest take either 5/16" bits, or 1/4" bits or thereabouts.
My first concern is how do I set this up? Assume I want a 3.125 inch hole, +-.005. Is that possible with the way these bits are held/clamped?
Second concern is that the rip cutters do not appear to hold the bit at an angle, which may make it difficult to cut thick materials.
What's the best way to go about this? R8 or straight shank is acceptable.
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Fly cutters aren't normally used as a boring head, although it's not impossible. The big problem is the obvious one. You have little control over the size of the hole you'd like to bore. Remember, half a thou movement of the tool translates into a thou on the diameter. Holding .005" would then restrict you to moving the tool within only a .0025" range. That's pretty hard to do, especially if you're not well experienced.
Bottom line: You aren't really looking for a fly cutter, you're in the market for a boring head. Fly cutters are generally used to take facing cuts on flat items. Boring heads are used to make turns or to bore holes.
I'd suggest going with the R8 shank for rigidity.
Harold
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Harold & Susan Vordos wrote:

Pick up an edge for reference. Move away from edge amount equal to radius of desired hole. Install flycutter into spindle. Set tool to just contact edge. A little care and quite accurate sizes can be attained.
michael
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