Bit by the Helix Monster

MrWhoopee

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Doing some roughing on the mill yesterday with a 3/8 HSS rougher. I needed to make two passes, almost full width and .550 deep and 3 inches long. Feeling brave, I decided to take each in one pass. The material was 4140HT, at 325 rpm and modest feed the first pass went smoothly. As I started the second pass I nudged the feed up just a hair. Everything looked good so I walked off to do something else while the cut finished. When I got back I found, to my horror, that the endmill had sucked down almost .200 while I was away. Threw the part in the bin, turned off the lights and went outside to do something I felt more qualified to do, chainsaw work on a downed tree.
 
Doing some roughing on the mill yesterday with a 3/8 HSS rougher. I needed to make two passes, almost full width and .550 deep and 3 inches long. Feeling brave, I decided to take each in one pass. The material was 4140HT, at 325 rpm and modest feed the first pass went smoothly. As I started the second pass I nudged the feed up just a hair. Everything looked good so I walked off to do something else while the cut finished. When I got back I found, to my horror, that the endmill had sucked down almost .200 while I was away. Threw the part in the bin, turned off the lights and went outside to do something I felt more qualified to do, chainsaw work on a downed tree.
Learned the hard way long ago. Never walk away from an operating machine. Soon as you do, Murphy's law kicks in. That's too bad, better luck next time.
 
I have only 3 machines I feel confident to run by themselves. Horizontal bandsaw, vertical bandsaw, and Atlas shaper. I saw firsthand what can happen on a vertical mill with them being sucked out of the collet. At that time I didn’t know about tool holders. The guy was supposedly a machinist and ended up making a 4” long trough in the mill table much to the boss’s dismay. Through a thread here on H-M I learned about tool holders and bought a set. Any time I’m removing a lot of material I use the tool holders.
 
I remember vividly my surprise when an end mill sucked down on me like that. I had thought it would go the other way.
That was a good lesson on machining forces. :)
 
An old trick I was shown a hundred years ago or so was to put Dykem on the shank then load it in the collet. It really worked out well:<)
What does that do for you? Just an indicator of movement out of the collet?
 
It makes it not slip.
Ah, ok. Could have used it while I was using a dovetail cutter. Dang thing pulled down and ruined the clamp I was making. Took the wind of of my sails, if you know what I mean. Good thing to know!
 
C-bag, a 4’ long trough in a mill table is never good. I suspect the boss had to walk outside for a bit.
 
C-bag, a 4’ long trough in a mill table is never good. I suspect the boss had to walk outside for a bit.
The worst thing was the trough was a direct indication of what happened as it ramped deeper as it progressed. I was too green to know exactly what happened and thought it was just not tightened enough. Later I would realize that wasn’t the problem. The only good thing was the 5” vise covered the trough. And yes the boss who had come up through the shop and had fought tooth and nail to get that Bridgeport into the packing house shop, walked straight out of the shop and jumped in his truck and took off.

I don’t mention any of this to bag on MrWhoopee, he’s forgotten more than I’ll ever know about machining. I just post it so other greenies like me can get a tip like I got from another thread here on H-M.
 
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