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.
...and I *do* appreciate warnings about high speed bits whirring around
at ungodly speeds, but only from those who are experienced making and
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
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.
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
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.
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
Spend the 40,
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,
ps: thanks again for good warnings
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....
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