Router Bit Modidfication

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Further to my wanting to put fluting around the edges of shelving, (and the answer is "Pin Router", thanks for that great tip), is it cost effective to get expensive router bits slightly modified? The fluting bit I have gives five beads at the one pass, but at each side of the beads, is a flat that is really in the way. Has anyone gotten something like this removed by professional sharpeners? Was it cheap? Was it satisfactory? I am loathe to grind the bastards off myself cos of balance problems, but what about spinning the bit in the router and judiciously grinding the little carbide flats of with a suitable corundum stone? That should keep the balance right, No?
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I would not recommend modifying carbide bits and carbide needs either diamond wheels or else very soft 'green' stones. I believe your suggestion of spinning the bit in the router is a recipe for disaster. As a machinist the stationary tool is invariably offered to the grinding wheel, the feed mechanism is graduated in 1/10 of thou and better.
For your application I would suggest you look for suitable high speed steel bits and if the profile is not exactly what you need those can be ground with a Dremel or similar. Providing the diamater is quite small the out of balance component will be almost negligable.
Bernard R
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On Thu, 13 May 2004 00:22:15 -0500, "Bernard Randall"

Thanks Bernard. I sort of suspected so. Just out of interest, what are "very soft 'green' stones"? Out of curiosity, what is likely to go wrong with spinning the half-inch-shank bit in the large router, well secured in the router table, and applying the stone judiciously to it? I remember years ago on the metalwork lathe sharpening the carbide tipped tool by hand on the carborundum grind wheel. Worked a treat IIRC.
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Sandy wrote:

For one thing, if you're not _very_ careful you'll find that the carbide cuts the stone very nicely if it doen't hurl it across the room in pieces, hopefully lodging in the wall and not in your gizzard. When you were sharpening that tool on the lathe, you were turning the stone, not the cutter, were you not? And did you just jam the point of the cutter into it or did you sneak up on it from beneath?
If you're going to do this, do not try to use the router to spin the tool (if you need to use it as a positioning aid that's another story but be careful about getting it full of filings), and make up a jig that lets you repeat the same motion on all flutes so you end up with a consistent cut and good balance. At 20,000 RPM it doesn't take much unbalance to cause things to come apart, and I've seen a chunk of carbide hurled by a rotating machine go right through a Navy landing craft (there's a reason it's used in armor-piercing ammunition).
As someone else pointed out, you'd do better to start with a steel tool than carbide--machining carbide is a specialized art. Unless you're going to be doing an awful lot of this or are working with a very abrasive wood the steel tool (assuming it's good quality and not consumer-grade crap) should hold up just fine and if it's properly sharpened may even give you a little bit cleaner cut.
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In general, hard materials should be ground on a relatively soft wheel, and vice-versa. The first letter on a grinding wheel designation is the type of abrasive: A for aluminum oxide, C for silicon carbide, GC green silicon carbide. On the occasions I've run 'green' stones there's dust everywhere....
If you run a carbide bit into a stationary stone you'll cut the profile in it. If you had both the router and grinder running you stand every possibility of the router biting off a large enough chunk of the wheel to jam the wheel and it will litteraly explode - extremely dangerous.
The problems you face running the router and applying the stone to it are 1) a carbide tool will profile the stone not vice-versa 2) the grinding dust will get everywhere, possibly also into your router 3) any profile you do get will be normal to the tool, i.e. no cutting angle, so those portions of the tool will burn your surface, not cut it.
When machinists do off-hand grinding it's always with part of the tool resting against a solid tool rest becase the action of the grinder is to pull the tool into the wheel. The gap between the tool rest and wheel is kept very small to prevent anything jamming the wheel, exploding wheels are a very real danger, and experienced machinists always tap wheels before mounting them to ensure they 'ring true'.
Bernard R
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On Thu, 13 May 2004 11:06:27 -0500, "Bernard Randall"

Thanks, I didn't know that -- sort of counter-intuitive.

Thanks for that. I've just found a full key to this code and find my two grinder wheels are Alumina.

Thanks, good warning :)

Thanks again. I had no intention of poking a stone at my spinning router bit. I would have had both elements securely clamped and offer the stone to the bit via the fine height feed of the router.

This bit is cylindrical with the profile longitudinally down the long edges of the cylinder. I would not want to touch the profile other than the two small flats at each end of it. I was intending to grind away the top of the cylinder (2mm) until the beading profile was reached, and then judiciously remove carbide from the bottom of the cylinder (ajacent to the shank) until the small 2mm flat is removed.

Good warning -- thanks

As I explained above, this won't apply. The carbide I would be removing would not then touch any work piece. I'm trying to leave the profile section intact while removing the small flats at each end that will be in the way.

Thanks once again. I was always taught to stand to the side of any wheel being powered up.
Anyhow, after all the good advice I've received here, I think I will price the mods I want at the local saw doctor (Carbide sharpener). Thanks to everyone :)
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Once upon a time (mid '70's), in high school auto shop, a kid in my class asked the teacher, "Can I make my own camshaft?" The teacher thought about it for a moment, and said, "Well, sure. Just get a big chunk of steel, and cut away everything that doesn't look like a camshaft."
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On Thu, 13 May 2004 00:52:32 -0500, "Jerry Shaw"

That's what Michaelangelo did with large lumps of marble. Just removed the bits that didn't look like what he was aiming at. If it were that simple :)
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I'd either use what is available, or have a custom tool made. I'm sure there are plenty of sources, one is Ridge Carbide. www.ridgecarbidetool.com They can do it, but I have no idea of cost.
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I've modified a few carbide bits. I try to use HSS if I'm going to modify even if it does require resharpening more often. The way I've made the modification is to chuck the bit in a 6 inch Atlas lathe and engage the back gear for slowest speed. I then mount a Moto Tool on the cross slide with a diamond stone mounted in the Moto Tool. I then grind by eyeball (nothing scientific about this part) to a pencil line I've drawn on the carbide of my desired contour. Results in no problems with balance.
rhg p.s. I think you'll be disappointed in trying to do it with carborundum. The stone will grind away almost as fast as the carbide - maybe faster.
Jerry Shaw wrote:

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What size of diamond wheels are you using? Are they reasonably priced? Do your dry grind or use some form of lubricant. I got a large diamond wheel for a grinder at auction, but generally prices have put me off, but I'd like smaller sizes for the Quorn T&C grinder I'm building.
Thanks
Bernard R
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On Thu, 13 May 2004 16:51:09 -0500, Robert Galloway

Thanks Robert. Interesting. I've decided to take it to my local sharpening shop.

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the thought of taking a spinning router bit and :"judiciously grinding

by a cutter.
I think that tryingt o midifya router bit like that is different from working something on a grinder - on the grinder, the spinning surface is a surface - once the piece is in contact, it'll stay in contact. When the router bit is spinning, the only part that you'll be touching is the edges of the bit - kind of like the difference between touching the surface of a spinning bicycle wheel and a propellor...... Sounds like a recipe for a trashed stone at best.....
goodl uck --JD

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posted:

Well howsabout clamping it to the router table and just touching the flats onto the clamped stone with the router's height adjustment?

Not always, in my experience, DAMHIKT :)

Not quite sure why. You need something to be moving fast, and something to remain fixed. If both are adequately restrained....

Thanks.
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It has been explained in previous post that this will likely result in a pulverized stone (which IS highly likely) and, if it did work. would result in NO cutter relief causing the tool to cut badly or not at all. If you need this done, take it to a professional tool grinder. One that does metalworking tools. Take them the bit, tell them what you want and they will tell you if it is feasible with that cutter or not. They have the equipment and know how to do this kind of work.

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posted:

Yep, good advice which I intend to take. Thanks. See other responses of mine to explain why the cutter relief is irrelevant, and why my stone would not likely have broken up.

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Instead of grinding a new bit, is there any other option? Like gluing a strip of cheap pine to hardwood, with thick brown paper (from a Shopping bag) in between. Then remove the strip.
Or else do the routing in more than one pass.
I'm not an expert. But I see what patterns can be made with multiple passes from router bits, and it always impresses me.
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Any machine shop can do a simple modification like that for you in just a few minutes. It will be cheap IF you find the right guy in the right shop.
If this is your typical fluting bit, an inch or less in diameter, balance won't be a big deal if you take even a little bit of care. I would grind it myself by hand, but it would be at work, not on my home grinder.
-- ******** Bill Pounds http://www.billpounds.com

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On Thu, 13 May 2004 18:09:27 GMT, "Pounds on Wood"

Thanks, Pounds :)
What would you grind it on?
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We have an extensive machine shop at work, with wheels specifically for carbide, and would use that if doing it freehand. We also have endmill sharpening equipment and if I wanted a perfect job would use that. None of this is equipment that I would have at home or any woodworking shop.
-- Bill Pounds http://www.billpounds.com/woodshop
posted:

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