# End Mill sliping



## kvt (Dec 22, 2017)

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.


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## woodchucker (Dec 22, 2017)

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.


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## mikey (Dec 22, 2017)

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.


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## markba633csi (Dec 22, 2017)

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


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## Bob Korves (Dec 22, 2017)

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.


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## EmilioG (Dec 22, 2017)

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.


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## Bob Korves (Dec 22, 2017)

Also make sure your drawbar is not too long and bottoming out in the collet before it draws the collet far enough to grip the work.


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## ezduzit (Dec 23, 2017)

Don't know what an RF30 is, but can't you use a proper end mill holder instead of the collet?


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## kvt (Dec 23, 2017)

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.


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## Bob Korves (Dec 23, 2017)

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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## rgray (Dec 23, 2017)

ezduzit said:


> but can't you use a proper end mill holder instead of the collet?




In my book the collet is the proper end mill holder.


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## Mitch Alsup (Dec 23, 2017)

Resharpened end-mills are often out of tolerance of the collet size they were originally.


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## Bob Korves (Dec 23, 2017)

rgray said:


> In my book the collet is the proper end mill holder.


I guess you never had one let the end mill suck down into the work...  It would not happen with a Weldon end mill holder, used properly.  Mounting in a collet can be more accurate, is quicker, and used less headroom, but it is really only suitable for lighter work.  Weldon end mill holders are stout, but are also another place to add (or reduce) runout, and use up more headroom.  I use Weldon holders whenever I have a job that will put a real load on an end mill or other tool.


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## ezduzit (Dec 23, 2017)

Bob Korves said:


> I guess you never had one let the end mill suck down into the work...



That is how I learned.  Fortunately it did not ruin the part or my work holding equipment.


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## kvt (Dec 23, 2017)

Ok,  How does having an end mill sharpened change the shank diam.   Or am I missing something.  I know it shortens them a little, and also if the diam is sharpened then that changes.  Am I missing something.


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## mikey (Dec 23, 2017)

You are not missing anything. Re-grinding an end mill does not include the shank.


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## woodchucker (Dec 23, 2017)

Mitch Alsup said:


> Resharpened end-mills are often out of tolerance of the collet size they were originally.


Why would that be? They sharpen the flutes, not the shaft!
That would make no sense for a resharpening service to ruin an end mill that way.


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## JayMcClellan (Dec 23, 2017)

Bob Korves said:


> I guess you never had one let the end mill suck down into the work...


Done that! Here's a video I made of a T-slot faceplate project a while ago and at 2:45 is where I discovered that my slot was a lot deeper than I intended, just got lucky that it didn't go all the way through and cut into the table. No matter how much I cleaned and tightened the R8 collet it just wasn't enough to keep this roughing end mill from slipping downward even though the nominal shank diameter matched the collet. This is what convinced me to switch to end mill holders and they've been working a lot better for me.


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## rgray (Dec 23, 2017)

Bob Korves said:


> I guess you never had one let the end mill suck down into the work



Nope not yet.
And to think they now have heat shrink end mill holders.


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## Bob Korves (Dec 23, 2017)

rgray said:


> And to think they now have heat shrink end mill holders.


I will let that one gestate for a while and see what people think of it...


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## Bob Korves (Dec 23, 2017)

rgray said:


> Nope not yet.


There are those who have and those who will...


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## rgray (Dec 23, 2017)

Bob Korves said:


> I will let that one gestate for a while and see what people think of it..



Check this out.


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## Bob Korves (Dec 23, 2017)

rgray said:


> Check this out.


Thanks, Russ.  I actually knew about that once, interesting.  I had forgotten about them because it is highly unlikely I will ever have that setup in my humble home shop.  John's shop is a bit more high end than mine...  I am quite sure that it is a very good method of holding tools, and concentrically.  You could end up with a whole lot of expen$ive tooling that way...  Great for the pros.


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## rgray (Dec 24, 2017)

Bob Korves said:


> I had forgotten about them because it is highly unlikely I will ever have that setup in my humble home shop.



Yah I think he mentions a price for that heating machine and it's more than my brand new 12x36 lathe cost.
But we can dream ...right!!!


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## chips&more (Dec 24, 2017)

Well I guess I’m one of the outsiders that can say I do not have any problems with holding cutters in R8 collets. And I have been doing this for a very long time! I use a locking pin but not on purpose, it’s just there and I have not removed it. The pin can make a real mess of things if the collet/holder spins. Has not happened to me but I have seen the damage on holders and it’s ugly. I do not have a power draw bar. I just tighten by hand and not gorilla tight. I’m using the same draw bar for decades and the threads are still good. I do periodically clean the draw bar threads and collet threads. My collet set is Bridgeport. Most if not all of my cutters are USA. I can’t ever recall a cutter not staying put in the collet…Dave


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## kd4gij (Dec 24, 2017)

Sounds like a dull end mill.


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## 4GSR (Dec 24, 2017)

If the end flutes and or the corners of the end mill are slightly dull, this could add to the issue of it moving upward in the holder.  Also, I've had the quill move on me, even with the quill locked down.  Usually, the end mill at this point breaks off.


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## kd4gij (Dec 24, 2017)

Ken has a very good point. If you are lowering the quill and locking it down. Then the quill may be moving.


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## kvt (Dec 24, 2017)

I though of the quill moving after locking, so I even held onto things and watched gauge to see that it was not moving.   
begining to think it is the end mills causing the problem. Have no way to sharpen them At this point.   Am now thinking of trying to make a tool grinder setup at some point.   Anyone know where to get end mills and a low cost.    Ken


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## 4GSR (Dec 24, 2017)

kvt said:


> ..........................................  Anyone know where to get end mills and a low cost.    Ken


I'll be glad to help you out.  
I have a bunch that have been resharpen.  Be glad to send you a few.  PM me your address and I'll put them in the mail later this week.  I promise not to change my mind. Glad you got a mill.

Ken


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## kvt (Dec 24, 2017)

Ken Thanks,   PM sent


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## HBilly1022 (Dec 25, 2017)

4gsr said:


> I'll be glad to help you out.
> I have a bunch that have been resharpen.  Be glad to send you a few.  PM me your address and I'll put them in the mail later this week.  I promise not to change my mind. Glad you got a mill.
> 
> Ken



What a *generous *offer!!! This truly is the most friendly machining site on the web.


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