Brazing/welding router bits: experience?


I need to modify a 1/2" router bit. The profile doesn't have to be altered. I simply want to take a standard ogee bit and turn it upside-down to make a cope cut under a tenon (i.e., mated right up to the tenon), which requires removing the nut and washers, and cutting down the threaded post until it's under the carbide cutter height, then welding the bit to the post.
I think brazing it on should work OK, but I'm curious if anyone out there has had experience with this sort of bit modification.
Thanks, H
...and I *do* appreciate warnings about high speed bits whirring around at ungodly speeds, but only from those who are experienced making and modifying them.
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Wouldn't this cause the cutter to be spinning the wrong way?
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Darn, that didn't even occur to me. Thanks, this is the sort of caveat I need. I'll check the bit when I get home. Regards, H.
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There's also some companies making insert bits, so I'm thinking you can order custom profiles. But I've only seen the inserts for the rabetting bits, I believe.
--
Clint
"hylourgos" < snipped-for-privacy@sasweb.org> wrote in message
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I don't know your skills or your equipment, but most of us would end up with an out of balance slug of metal that may fly around the room in little pieces. Contact Ridge Carbide Tools (they have a web site) and tell them what you want. They make custom bits and this would not be a problem for them.
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It's an easy weld as far as balance is concerned, since the post keeps it straight, and I would first tighten the nut to "seat" it, tack it from the bottom, then remove the nut, cut off the post and braze the bit on the top also.
There are many companies that have the bit I need (this is for a window sash job), but they are usually sold in pairs (I don't need the one combined with the rabbeting bit), and they are fairly expensive (about $150/pr).
Amana has one (i.e., just the profile bit) that's on sale now for $40, so I may have to go that route. But for me, $40 is an outlay I'd rather avoid if I can modify what I have on hand.
Regards, H
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hylourgos wrote:

Man, at 20k, I'd sure be behind my shrapnel shield when I was running that baby!
Personally, I don't think this is a good idea at all unless you're able somehow to screen/test it safely.
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hylourgos wrote:

    I dont know what your experience is with welding, brazing, and the like but am assuming by your post that you have never tried to weld a piece that will rotate at any sort of speed. I have personally been welding and brazing for over 20 years and I have _never_ been able, nor seen anyone able, to weld or braze any item which rotates at even very low speeds (lets say around 1000 rpm) which didnt need machining after fabrication. For high speeds this would be followed by machine balancing. You are talking of an item that will spin at 20x this speed in close proximity to your internal organs.     Whether the weld is simple or not is irrelavent. It is physically impossible to weld/braze/etc, and come out with a piece that is in perfect balance (for a 20,000rpm application) even if you are the luckiest person on the planet. Furthermore you wouldnt be able to rely on the post as your sole source for alignment of the shank to the body. This is all moot as it has already been brought up that the rotation will be backwards and reshaping/resharpening for that will be equally as difficut. Other issues would be distortion due to heat. The heat of your fabrication effecting the bond of the carbide segments (more bullets) to the body itself. The list goes on.     To even contemplate blowing a hole in your stomach or some other bullet-like catastrophe when you say you are simply trying to save $40.00 sounds a little crazy. The risk isnt even worth the $150.00 for the set.
Spend the 40, Mark
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You're obviously right in so many ways, Mark.
I've done a good bit of welding, but I haven't ever done high speed components that need subsequent machining. Once you pointed it out, the difficulty was easy to recognize.
Elvis also rightly pointed out the possibility of not being able to reverse the bit (which is a problem with my bit. Some bits for sashes, btw, are made to be reversible for this very reason), but I still don't understand why, if balance weren't an issue, the post wouldn't provide sufficient alignment. I would tighten the nut, tack the bottom, then remove the nut, cut down the post and braze it there. The alignment should be fine because of the bottom tack, which holds it in the same position as the nut did before, no?
I had considered heat distortion. I think brazing with a small enough tip could avoid damaging the carbide, and I suspect the original brazing would be just fine too, but it is a risk.
Gotta suck it up and shell out the $150....
That, or make the sash windows without mortise and tenon joinery, which I really don't want to resort to.
Less wealthily yours, H
ps: thanks again for good warnings
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nope. that tack itself will pull the bit out of alignment. metal shrinks as it goes from a liquid to a solid.

I think some of the bottom end bits are brazed after sharpening, but everything worth having is brazed then ground.

yep.
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snipped-for-privacy@all.costs wrote:

Won't the tightened nut (and the post, which is still there and a tight fit) keep it aligned?
BTW, I took stock last night and just don't have the $150 to spare, so I'm going to cut off the tenons and use either loose tenons, dowels, or even biscuits (leaning toward dowels right now) with the el cheapo router bits, which will do mating cope cuts correctly as long as there are no tenons getting in the way.
Lesson learned about bits....
Regards, H
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