End Mill sliping

kvt

kvt

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Ok, Just got a RF30 and was trying to work on a piece of Steel. Using an 1/2 inch End Mill, in a 1/2 inch r8 collet. but in going across the piece I noticed that by the end of it, the end mill was not cutting really. Brought it back down to where I started and noted it was not touching. As it moved down the material it was sliding up into the collet. Ok, second try, I cranked down on the draw bar then tried again. Ensured it was a slower speed and feed, Same results It is like it does not work. On all the ones I have used prior I had collet holders on them. Is it normal for them to not hold in collets, I'm normally using much smaller things, (Sherline 5400 mill)
Any help/advice would be greatly appreciated.
 
Interesting, normally the endmill would pull down into the work. The fact that it is climbing back in is wierd. Is the mill spindle turning in the correct direction? Or is this a downcut end mill. Commonly used in wood working to prevent lifting ply. I have not seen one for metal, but maybe I'm wrong.


Do you have a end mill holder? its a holder that uses a set screw to hold the weldon flat. If it's a carbide endmill the endmill will not have a flat, and that makes it harder to hold.
Not sure what you mean by collet holder? an R8 is a collet, an ER32 is a collet.
 
It sounds like the 1/2" R8 collet is not holding the end mill solidly, despite tightening the draw bar. Is the end mill really a 1/2" OD? An R8 collet has a limited capacity to tighten below its rating. Also check the collet to see if it is damaged in any way or try another collet.
 
Try lubing the collet and the threads on the drawbar but NOT the shank of the endmill. Tighten it up pretty snug and try again
Use some oil on the cutting edges. Let us know how it goes.
Mark
 
R8 collets can only hold work or tools about .005" under the nominal size, and the closer to nominal the better. If the cutter shank is actually 12mm, a 1/2" collet will not hold it.
 
This is what I worry about with the out of spec r8 collets. I'm having a similar issue with a new Hardinge r8 1/2" collet.
I haven't used it yet. The fit is so sloppy, that I worry that slipping will occur. Generic collets are probably even worse.
Bob is correct, and the r8 specs must dead on or tenth or two under nominal. Does the collet hold the tool without slipping out
before you put it in the spindle? or, the OD taper may be too small. Either way, you get a bad collet.
 
Don't know what an RF30 is, but can't you use a proper end mill holder instead of the collet?
 
Thanks for all the input. The end mill fits snugly in the collet without falling out prior to tightening, Did oil the threads and the outside of the collet. The draw bar is does not bottom out prior to full tightening, verified it on the threads. Do not have any r8 endmill holders, have started looking for some. Was using cutting oil on the steel also.
 
I try to keep the inside of my R8 spindle dry, no oil ever. Collets likewise. They need all the help they can get to keep from spinning, R8 is not a very robust system for mounting collets in a mill. The anti-rotation screw, if you have one, is only really an aid to installing collets, depending on who you ask. It will shear off if it gets a real load on it, and replacing it is a real job on some mills. Some prefer not to have the anti-rotation screw in the spindle. I have had both with and without, and can live with either. Friction of collet to spindle is what keeps the collet from slipping
 
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