"rangerssuck" wrote in message
...
On Monday, July 21, 2014 4:13:23 PM UTC-4, rangerssuck wrote:
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.

Thanks for the input so far, and here are some answers to the questions that
were raised:
1) The project is modifying the double-hung windows in my house to work with
replacement jamb-liners. These are spring-loaded and are the mechanism from
jeld-wen windows, purchased from an outfit in Milwaukee. They used to sell a
router bit for the purpose, but they say they can't get the blanks anymore -
what they were actually doing is modifying an HSS v-groove cutter that has
been discontinued by Sears. I had purchased a bit from them and it's done
OK, but then I hit a nail and even though I've resharpened, it's not going
to put up with that too many times and I have 25 more windows (50 more
grooves) to do. The material I'm cutting is chestnut oak.

I have to do these windows one or two at a time, as the whole job is kind of
big and I don't want to disassemble all 25 windows at once.

I have a router table (shop made) set up to do this with the appropriate
fences and feather boards, and I'd much rather not have to switch bits for
each cut. I imagine that two passes (3/8 straight) and a 45 v-groove with
the bearing removed would probably do a great job, but it's either a bit
change or a second machine. Also, having standard-size cutters (and carbide,
too) would be a major plus.

As for the spade bit being only a 1/4" shank, the router (and bit) that I
have now is 1/4" shank, and that's not a problem.

What I would REALLY like is a shaper table to do this, but that's not in the
cards now, and would still involve either two passes or a custom cutter.

If I could come up with a way to do a quick-change of the bits (straight &
V) that would get them to the same height (perhaps a small collar under one
or the other if they're close to begin with the bit-switching wouldn't be so
bad. If I have to adjust the height each time, it would be a bitch - my
router table doesn't have a lift mechanism.

But back to the original question - is there anything inherently bad about
using a modified spade bit in a router? Would it be likely to fly apart at
speed if it was slightly off balance? [I've done some design work on
controls for 90K RPM motors and seen some spectacular failures]

A paddle bit will twist up as soon as it hits the wood and screw up the job
and probably put your eye out.

I assume you are plowing the sashes to fit the patent balance.

From the dimensions and the descriptions of the modified tool this angle is
close enough to 45deg to be designed that way.

Don't reinvent the wheel.

Buy a 5/8" 45deg. v-grooving bit. Blunt the end to around 3/16 and cut in
two passes.
http://www.mlcswoodworking.com/shops...-Groove_Anchor

The blunted end will leave the bottom fuzzy but it probably won't make any
difference because the sashes probably locate on the bevel before they
bottom out on the flat.

Paul K. Dickman