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]