# How not to run a milling machine



## DPittman (Jun 24, 2020)

well I imagine I'm going to be able to put together a nice list learned from personal experience.  

I was trying to cut a dovetail with a fly cutter and apparently the tool bit can be pulled out/down while cutting because I skimmed my shiny new vice jaws, OW that REALLY hurt.  I had the knee and quill locked.  I had to work really close to the jaws to begin with but I didn't think of movement of the tool bit.


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## Tom Kitta (Jun 24, 2020)

No matter how hard you try crashes do happen to everyone. In fact the more you run machines the more crashes you have - at least for me. Sure you learn from each one of these what not to do but sometimes you forget these lessons.


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## DPittman (Jun 24, 2020)

Yup this holder ain't going to work.

Fortunately I started with a practice work piece but unfortunately I did not have a practice vice. I imagine I will make much bigger mistakes in the future as Tom indicated is hard to avoid sometimes.


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## Janger (Jun 24, 2020)

ah alas. not a biggie though and quite common. Keith Fenner has a segment on you tube where that same thing happened to him while milling a key way. The key way ended up sloped from one end to the other. He has 40 years of professional experience. Alex likes the shrink fit tool holders - you don't have a problem with those pulling out tools. 

Last time I had a crash a carbide spot drill brushed against a bolt being used as a fixture. ( I was chamfering an edge 45 degrees). The spot drill spun the bolt out of the hole and the head smashed off the drill. Then I did it again a few days later!


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## Tom Kitta (Jun 24, 2020)

My last crash about a week ago involved accidentally running carbide endmill backwards. And just like that it shattered.


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## RobinHood (Jun 24, 2020)

Yup, stuff happens.

@DPittman : if you grind a little grove (with an angle grinder cut-off disc for example) on the side of your HSS tool bit where the set screws are, they will have something to bite into and the tool will have a much smaller chance of being pulled out. You could even switch the set screws out for dog point ones temporarily for this job. Also, make sure you have lots of clearance behind the cutting edge in all directions. If the tool back rubs even a little bit, the tendency to pull out is dramatically increased.


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## DPittman (Jun 24, 2020)

Thanks th


RobinHood said:


> Yup, stuff happens.
> 
> @DPittman : if you grind a little grove (with an angle grinder cut-off disc for example) on the side of your HSS tool bit where the set screws are, they will have something to bite into and the tool will have a much smaller chance of being pulled out. You could even switch the set screws out for dog point ones temporarily for this job. Also, make sure you have lots of clearance behind the cutting edge in all directions. If the tool back rubs even a little bit, the tendency to pull out is dramatically increased.


Thanks those are good suggestions.  I know I did not have the grind right and I think if I had a straight tool/flycutter it would have helped also. I think i might be needing a real dovetail cutter.


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## kylemp (Jun 25, 2020)

You didn't hit the table and jaws are replaceable. That's just an apprentice mark now.


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