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| Holy CR@P Batman!! http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10106&t=26876 |
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| Author: | Shane Neifer [ Wed Apr 07, 2010 2:35 am ] |
| Post subject: | Holy CR@P Batman!! |
Ya know how when some things happen you sometimes start to think about the "what ifs"? Well I was just milling some birch, light passes, .030 stepover, using the Amana insert bit, a 1" ballnose. I have used this bit for probably more than a dozen radius dishes and it works GREAT (thanks again Nelson!). Well, I was working a few feet away from the CNC (I means like 3 feet or so), then all of a sudden all of the sounds changed! This was the result: Attachment: Broken Cutter.jpg I am not sure what happened but probably one of the set screws for the inserts came loose, allowing the bit to drop and dig in and then it broke, taking the other insert with it. I was doing passes at 225 ipm and 18,000 rpm. I found these pieces (bits of both inserts) and the rest may be in the vacuum or embedded somewhere in the shop. Then it hit me (not literally, thankfully!), shards of broken carbide flying around a 330 sq ft shop from a shaft spinning at 18,000 rpm. Nothing about that sounds fun! So I will be checking and tightening the set screws on a very regular basis. I may also make a bit of a screen that hinges up on the front of the machine just to deflect any further possible flying objects away from the rest of the work area. Anyone else have any issues with insert bits? Shane |
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| Author: | Terry Stowell [ Wed Apr 07, 2010 7:20 am ] |
| Post subject: | Re: Holy CR@P Batman!! |
Yikes! I get it... Grateful you weren't hurt. Coulda be serious. |
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| Author: | Dennis Leahy [ Wed Apr 07, 2010 8:24 am ] |
| Post subject: | Re: Holy CR@P Batman!! |
Wow, that was close! Will 1/4" polycarbonate stop a chunk of carbide shrapnel? Dennis |
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| Author: | npalen [ Wed Apr 07, 2010 9:36 am ] |
| Post subject: | Re: Holy CR@P Batman!! |
Sure puts a lot of value on safety glasses. (Maybe a bullet proof vest also) Nelson |
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| Author: | Stuart Gort [ Wed Apr 07, 2010 12:47 pm ] |
| Post subject: | Re: Holy CR@P Batman!! |
Hmmm......let's see. 1" diameter x 18000 rpm = 56548 inches per minute = 942 inches per second = 78 feet per second = less than 1/10th the speed of a good pellet gun. A blunt edge wouldn't break the skin but a sharp piece might if it had a little heft to it. Not TOO dangerous but wear your safety glasses. 
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| Author: | Stuart Gort [ Wed Apr 07, 2010 12:49 pm ] |
| Post subject: | Re: Holy CR@P Batman!! |
Dennis Leahy wrote: Wow, that was close! Will 1/4" polycarbonate stop a chunk of carbide shrapnel? Dennis Depends on the weight ..... but ya..... figure on it. |
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| Author: | Shane Neifer [ Wed Apr 07, 2010 1:37 pm ] |
| Post subject: | Re: Holy CR@P Batman!! |
Thanks for the calculations Stuart, now I lost sleep over nothing! Although, even if permanent damage was not probable, I am sure that it would still hurt like heck! Therefore I would much rather keep them things where they are supposed to be and doing what they are supposed to be doin'! Shane |
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| Author: | Bob Garrish [ Wed Apr 07, 2010 4:27 pm ] |
| Post subject: | Re: Holy CR@P Batman!! |
1/4" of lexan will stop them just fine. Much larger things have bounced off the windows of the Fadal 
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