end mills (breaking)

Gene,

1/8" is very small and super easy to break...period!

HSS is tougher and more forgiving than carbide.

Watch your backlash if milling a pocket...maybe the tool is climbing when you reverse directions due to slop in the slide. You can tighten/lock the slide just before reversing to help prevent this. Also, take lighter cuts... if you are milling the full 1/8" width, go .020"-.050" deep per pass. The corners on inside pockets can always be tough.....patients, patients, patients!

Excessive chips can jamb the tool and break it....keep the chips clear and lubricated to prevent/reduce recutting and jambing.

Generally I prefer 2 flute mills for deep pockets/slots that have very little room for chip evacuation. 4 flutes on outside/perimiter work.

In a manual mill, it takes a gentle touch and experience...when in doubt, go slower and lighter.

Good luck,
Rob
 
Milk Man, we break one a year. Come up to the shop or give us a call 803-794-6067 and we'll tell you/show you how we do it. We aren't but about an hours drive from each other. The Cavelady
 
Thanks for the milling tips Rob!!!
I have a question about milling closed slots in guards.
Should I push the mill thru on the ends when I start out or just go ahead and mill the entire slot?
I've been making the thru cuts on the ends to help reduce creep length wise but I've wondered if this was a good practice or not.
 
If you're milling through slots, use a drill bit to drill through one end first. Then, feed the mill down at the hole location for each pass. This eliminates the problems you can encounter while plunge cutting with an end mill.
 
Everything rfrink said,pluss keep you'r end mills as short as possible and keep the runout to a minimum,don't let them chatter and especialy in stainless steels don't let them dwell in one spot or feed too slow.They don't give much warning when theye'r about to break.Make sure you are using the right spindle speed and feeds,for the material you'r cutting.There are many charts and tables to help with this.Keep the chips out of the cut with coolant and or air.Four flute e.m.'s have a thicker cross section of material per diameter compared to Two flute e.m.'s and will take higher feeds in harder materials as long as they'r not loading up with chips.A properly adjusted air mister is a good way to go.Also change the e.m.befor it gets to dull i.e.wont dig into your fingernail easily.It is true carbide will not flex much befor it brakes but when used properly it will out last high speed steel many times.You didn't specify if you were using a manual or cnc machine it does make a diff.If you are useing a manual machine try to keep your cuts conventional not climb milling.Climb milling gives a better finish but is very hard to do on a manual machine due to backlash in the lead screws,tightening the gib screws does help some what.Good luck
 
L6, we have a couple machinists here. I enjoy reading their posts. I am not but have milled (attempted to) alot at home in the last couple years. So far, I have not broken an end mill but have burned a few:( .

If you do not have a DRO you might want to drill the two end holes of your slot if you can hit them within your tolerance. This way you will not have to worry about feed screw backlash - once you hit the clearing all you gotta do is backup to the start clearing and begin the next run. I go no more than 0.025 mil deep in nickel silver and I consider that chatter deep. MUCH less in steel.

Roger
 
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