According to Bill Schwab :
Don,
[ ... ]
A flycutter as supplied would not, but with some custom bit
grinding, it might work for a reasonably small workpiece thickness.
Thin work I have going for me.
That helps.
[ ... ]
I consider the boring head to be the better cleanup option.
Unless I encounter other priorities, I will probably have one before my
"production run" of this design. For now, I need to clean up a few
holes, and really not all that accurately.
O.K. Clean up *can* be done with a half-round file for just a
few holes.
Fair? Any recommendations on a hole saw?
Leonix? Starrett?
Thanks.
Hopefully, others will toss in more suggestions.
Do you intend to go all the way through, or to leave a shoulder
as shown there?
Through.
O.K.
[ ... ]
The angle of the bit will normally be more shallow than what you
have shown -- though that is probably more the limitations of ASCII
graphics than your mental image of the position of the bit.
My mental image is pretty limitedg, but yes, I realize the angle shown
is too steep.
Good enough. Just making sure. :-)
But
essentially, as you go deeper, the ground cutting edge on the bottom end
of the bit will not be the only thing which is contacting the workpiece.
You will add the sloped under-surface of the body of the bit, which is
not ground to cut, nor to have relief. This increases the amount of
cut, especially when you get to the projections between the holes which
you drilled to knock out the waste stock.
Could that not be avoided by taking multiple passes to enlarge the hole?
Yes -- with the problem that it is difficult to set a fly cutter
precisely to a given size, and with multiple holes and multiple passes,
you will have to do the same thing multiple times -- unless you fixture
the workpiece, do one pass for all workpieces, then increase and the
next pass for all, etc.
The boring head has a micrometer dial to give you repeatable
readings -- though it is still easy enough to get one turn off and be
too small (no real problem) or too big (I have yet to see a mill with an
"add metal back" feature. :-)
I _think_ I understand what you mean, and I first started to realize
it from Harold's initial reply.
Good.
[ ... ]
Granted -- you can grind a bit to follow a shape which will
approximate a trepaning bit for a boring head -- for fairly thin
workpieces.
Try something like this (again understanding the limits of
ASCII graphics in portraying the angle of the bit):
/ /
/ /
/ /
/ _ /
/ |
/________| --- this step must be greater than the
thickness of the workpiece
The actual angle of the bit will typically be less than 30 degrees to
the horizontal, so the necessary grind to clear the thickness will
probably weaken the bit somewhat more than is comfortable.
I think I follow. Suddenly it doesn't seem so bad, but the hole saw is
probably the way to go.
Thanks!!
You're welcome.
Enjoy,
DoN.
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