Glad you missed the shrapnel. Plus 1 on inspecting the bits prior to using them.

When I chucked up my new HF slot cutters the other month lets just say I would have put on a face shield if I had had one.

 

Its typical for a fractured bit

 

Not something that you'll want happening but sometimes really hard to tell before hand. Glad it wasn't anything more than a bad bit and no bloodshed to deal with.

 

The break looks all fresh so I have my doubts you would see any problem with it ahead of time.

 

I had the same problem with a brand new router bit from Rockler.
I kept it in its original package for several years.
When I wanted to use it, I found a small piece of carbide inside the envelope.
I never used the bit.

 

You were running a large bit at 18,000 RPM. NEVER! I alway run large bits at the slowest speed the router will run. I had a woodworking friend that did the same as you, but it blew his fingers off with it.

 

kywoodchopper

I get the impression from the picture that the bit isn't very large at all. But it is a good reminder to slow the speed down based on size of the bit. A reference that can be used is:

From Rockler's website

Router Bit Diameter Maximum Speed



Up to 1" 22,000 - 24,000 rpm

1" to 2" 18,000 - 22,000 rpm

2" to 2-1/2" 12,000 - 16,000 rpm

2-1/2" to 3-1/2" 8,000 - 12,000 rpm

Remember, that's just a reference; Always follow manufacturers recommendations and the sage advice that if something doesn't feel like it's working right, there's a good chance that it isn't. Better yet, pick up a Router Book and get to know your router inside and out.

 

It's an inch and a quarter bit, not too big.

 

I would also add I never use inexpensive tools. If I'm thinking of saving a few bucks by buying inexpensive I would first go to the nearest emergency room and ask for a rough price a reattaching 3-fingers. Whether it is a router bit, tablesaw or any equipment.

 

I run my 1 1/2" flat bottom cutter at 18k rpm every time I surface the spoilboard on my CNC. 18k rpm is within the range specified by the manufacturer. It definitely 'sings' at that speed but it works just fine and is very smooth.

David