Hit brass with router bit ... is it ruined?

[Wayne]

I am attempting to build a router table extension to my table saw. Due to a measuring error while trimming the edge of the tabel with a 1/2 x 1" carbide straight cut, I clipped the side off of a couple of 1/4 " brass threaded insert screws. The bit more or less milled the brass level with the side. There was a bit of a metalic hot smell and the bit and brass were quite warm to the touch.

On inspection I can see nothing wrong with the router bit. There is no discoloration from burning, no chips, and the edge feels smooth and sharp. The project does not even seem to be ruined.

I know brass is softer than carbide, but its sure harder than wood. Is the bit OK? Should I try touching up the carbide edge on the inside with a diamond hone?

Wayne in Boulder CO

[Steve Peterson]

You can machine brass with good tools, like carbide. Especially if you can't see any damage, there probably isn't there. Of course, it almost never hurts to hone your bits.

Steve

[Morris Dovey]

| I am attempting to build a router table extension to my table saw. | Due to a measuring error while trimming the edge of the tabel with | a 1/2 x 1" carbide straight cut, I clipped the side off of a couple | of 1/4 " brass threaded insert screws. The bit more or less milled | the brass level with the side. There was a bit of a metalic hot | smell and the bit and brass were quite warm to the touch. | | On inspection I can see nothing wrong with the router bit. There is | no discoloration from burning, no chips, and the edge feels smooth | and sharp. The project does not even seem to be ruined. | | I know brass is softer than carbide, but its sure harder than wood. | Is the bit OK? Should I try touching up the carbide edge on the | inside with a diamond hone?

Probably a good idea to check the bit with a magnifying lens. A touch up with an extra fine hone probably wouldn't hurt.

Next time slow the router and use coolant. Don't forget safety glasses. :-)

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[John T]

About the only thing I'd look for is any chips in the carbide. The carbide is WAY harder than the fairly soft brass. I don't think you'll have a problem.

John

[Owen Lawrence]

I did the same sort of thing building my router table. I was routing for the fence T-slot and ran into a steel hinge screw. I have no concern about the bit since it's clear that it "cut" the screw, rather than mashed it. The same thing happened once or twice on the table saw when I hit a nail. The nail was just as long as it was when I started, but only half as wide. In both cases sparks flew, but in neither case was there any difference to the cutting power of the bit or blade. Carbide is tough! YMMV.

- Owen -

[Patriarch]

"Wayne" wrote in news:- [e-mail]:

So how much would it cost to replace this bit, and forget worrying about it?

Patriarch

[David]

Not to worry, Wayne. Your bit is fine judging from the soft metal you said it encountered and your visual inspection bears that out.

Dave

[David]

You and I both know his bit is fine so why put doubts in his mind? If he had any remaining doubts all he needs to do is USE the bit and see that it cuts properly and requires no more effort to cut with than it did before the non-event of milling some brass.

Dave

[Upscale]

It's hard yes and maintains its sharpness, but it is prone to shattering on sudden impact.

[Owen Lawrence]

Oh, man! Now you've got me wondering exactly what "sudden impact" could possibly mean. At 20k RPM I would think almost everything happens suddenly. :) Let's do some arithmetic: We're talking 333 RPS. Suppose I'm moving at one inch/sec, with two blades on the bit, that's about one and a half thou per nibble. I don't know how fast the thing really turns when it's cutting, so let's say it goes 10k (a low estimate judging from the change in musical pitch); that's still only 3 thou at a time.

But point well taken. I certainly wasn't happy about hitting metal with my router bits, and except for screw ups (no pun intended) I avoid it. Nevertheless, I don't worry so much about it when it happens. I'm glad I've never had a carbide anything shatter.

- Owen -

[Upscale]

The carbide on router bits can break when they're accidentally dropped on the floor. That's the type of sudden impact that I had in mind. Carbide is extremely hard in one respect, but it has some weaknesses in other respects.

[Wayne]

Thanks to everyone for the replies. The valium goes back on the shelf! :-)

Back to work on the table. I will post a picture when its done.

Wayne

[David]

When you want a REAL thrill, hit a steel plate with a 10" carbide tipped blade in a TS! I never did find the 24 carbide blade tips, but I sure heard them hitting the inside of the saw, the pavement, etc! Luckily none decided to head my way.

Dave

[Patriarch]

David wrote in news: [e-mail]:

His bit MAY be fine, or maybe not. I can't tell from here. The question was more one of economics: How much money is it worth to put the question to rest? Is it a $15 blue wonder from Rockler, or an expensive spiral cutter from a leading industrial supplier?

He had the doubts, made a post asking a question, without any prompting from me.

Patriarch, with reasonable certainty regarding a few things, none of which involve spinning metal at 20k+ rpm...

[Morris Dovey]

| When you want a REAL thrill, hit a steel plate with a 10" carbide | tipped blade in a TS! I never did find the 24 carbide blade tips, | but I sure heard them hitting the inside of the saw, the pavement, | etc! Luckily none decided to head my way.

In the aircraft factory next door to my shop they use a miter saw for cutting aluminum. One of the new guys tried chopping some chrome moly steel tubing with it and stripped off all 80 teeth. I got a look at the remains of the blade and a handful of the teeth; and saw that all of the breaks were in the steel disk - the carbide teeth (and the carbide-to-steel bonds) were undamaged. The teeth were still sharp and none that I saw were chipped.

Solid carbide router bits bear a remarkable resemblence to the carbide end mills commonly used to machine steel, brass, aluminum, etc (the most common configuration is a spiral up-cut) and I regularly buy end mills for use in my CNC router because they're often less expensive and are available in more sizes than router bits.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Obfuscated]

Yes. The brass is shot. Send the router bit to me.

;-)