On Mon, 21 Jul 2014 21:19:55 -0500, "Terry Coombs"
wrote:

PrecisionmachinisT wrote:
"rangerssuck" wrote in message
...
I need to make (or have made) a custom router bit. The groove I need
to make is a truncated V 15/16" wide at the top, 3/8" wide at the
bottom and 1/4" deep. The dimensions aren't super critical, but
closer is better.

I do NOT have a real tool grinder, and HF seems to have discontinued
theirs. I also don't (as will become apparent) have more than a very
little bit of experience grinding tool bits. I DO have 1x30 and 4x36
belt sanders, a set of 5C collets and a square collet block.

I'm thinking that I could lay out the shape on a blank, hold it in
the collet block, set the fence on the sander to 41 1/2° (to form the
V angle), tilt its table to 20° or so (to form the cutting edge and
then grind to the line. Then grind the flat end and its cutting
edges.

Question 1:
Does the above sound reasonable?

I have found a source for HS blanks http://goo.gl/13G1cD but a)
they're not at all cheap and b) they have a half-inch shank and I
have a 1/4" router. I'm not opposed to a new router, but only if I
really need it.

Question 2:
Is there any reason I couldn't start out with a 15/16" spade bit as
my blank? Even the most expensive spade bit is going to be less
expensive than that router bit blank. Is there something about a
spade bit that would make it totally unsuitable for this?

Question 3:
should I just job this out? If so, is there anyone here who would
want to do it? How much should I expect to pay?

Thanks for the input.

===

Probably I would sacrifice an old center drill; spade bits typically
only have a 1/4 diameter shank and so they'll bend very easily if
subjected to much side loading.

Offhand grinding of this sort of tooling is made quite a bit easier
if you use a single flute design.

Won't a single flute cutter run into balance problems at 20,000 plus RPM's ?
It might at that. I have used single flute cutters at high speeds but
not 20,000 RPM. It would not be hard though to grind away material on
the other side of the cutter. This would limit how many times the
cutter could be resharpened but not by much.
Eric