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View Full Version : What happens when a bit breaks?



Keith Barkhau
09-28-2008, 3:07 AM
Hello All,

I am considering making the plunge into home CNC and was just wondering what happens when a bit breaks during operation? I'm assuming that this happens from time to time, especially with small diameter bits. Do you end up with flying shrapnel, or does the broken piece just embed itself in the workpiece? I tried searching on this topic and didn't find much so I'm guessing its not a big deal, but thought I'd ask.

James Jaragosky
09-28-2008, 3:58 AM
Hello All,

I am considering making the plunge into home CNC and was just wondering what happens when a bit breaks during operation? I'm assuming that this happens from time to time, especially with small diameter bits. Do you end up with flying shrapnel, or does the broken piece just embed itself in the workpiece? I tried searching on this topic and didn't find much so I'm guessing its not a big deal, but thought I'd ask.
It could go either way. depends on the material and the speed of the travel axis. people have definitely been injured from broken bits, but usually it just scares the he** out of you.

Kenneth Hertzog
09-28-2008, 10:14 AM
Keith

Since I've had my share of broken bits. they usually are sitting in the work piece. they very seldom fly with any force.
But I due where eye protection.
mine usually bread from to fast travel. and a little to much depth.

ken

james mcgrew
09-28-2008, 10:32 AM
i have had a few moments of shear terror when a small part gave loose while i was still learning !!! learned a lot about tabbing and work hold down after that!!

jim

james mcgrew
09-28-2008, 10:34 AM
james i have been told our machines will finnish at the same time!! i hope we'll meet again in lafayette!!

jim

Wil Lambert
09-28-2008, 6:37 PM
Most of the time the bits stick in the material. You are normally getting a break in the bit because of overload. Since the bit was overloaded it has too much material embedded in the flutes. This is a good thing for breakage since it helps hold the bit in the piece.

Wil

Keith Barkhau
09-28-2008, 6:56 PM
Thanks all--that at somewhat sets my mind at ease. I was just picturing having to explain to the ER doc that that hole in my arm really wasn't a gun shot wound....

Larry Bratton
09-29-2008, 7:22 PM
Been running a CNC router for about 5 yrs now and have broken a few bits over time, however, I can never recall a situation where the bit flew out of the work piece. Most times breaking a bit is operator error. Small diameter bits are certainly more susceptible than big ole 1/2" ers. Your safe, just use common sense and be careful when making your toolpaths for speed and feed.

james mcgrew
09-29-2008, 8:08 PM
larry i called joey today and found you had already spoken!

jim

Larry Bratton
09-30-2008, 10:19 PM
larry i called joey today and found you had already spoken!

jim
Jim,
Suprisingly the machine fixed itself! We had a loss of the Y axis after some sort of a mishap. I think we may have a worn 1/2" collet and it allowed the bit to drop. When it did, it bogged the router down, I was watching it and I immediately killed it. I shut the machine down, re-booted it, but I was showing a fault indication on the Y drive. After a couple of reboots etc., I still didn't have it back. I shut the whole thing down and went to the office to try and solve it.So, I decided to give you a call, since I had not had much luck with their phone # in the past. I tried again and I did connect and got Joey. I actually ended up talking to Bill later in the afternoon. He and I had a good conversation and remembered my machine. He gave me a couple of things to try, so I went back to the shop and brought the machine up from a "cold boot". Waaala!! no fault light and everything was back to normal!! I'm not technical enough with these things to expound on what may have happened there, but, I am relieved to be back up. I had some signs I realllly needed to get finished. May be the encoder for the servo.

However, this old Warthog machine speaks well to Bill's CNC manufacturing ability. I have had this machine for 5 years now, running the same software, and I have only replaced one part on it, a Z axis servo motor and I'm not sure I actually needed to do that. We found a loose wire in the wire harness that was causing a problem. The machine has paid for itself many times over. I would certainly do business with Bill again and am glad to see them getting cranked up on a new venture. He built my machine in that that same big ole red building behind the big house, that he's working out of now.

james mcgrew
09-30-2008, 11:09 PM
i am kinda happy with bill myself, i will have my new x3 in a couple of weeks or so i hope you'll come down and see it!! got you some corian saved too!!

jim

Larry Bratton
10-01-2008, 12:33 AM
I will, hopefully fuel shortage will abate by then.

Brian Peters
10-11-2008, 11:27 AM
Every situation is different but usually the bit will break and stay in that tool path, or drop on the table. I have yet to see one go flying. But with solid carbide tooling I haven't seen it happen a lot. Hell I have hit steel pan head screws and sliced through them like butter, very tough tooling when its solid carbide. But what happens? I think I would probably hit the estop before things got too bad.