End mill holder vs collet

C

cmv

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My mill has an R8 spindle. I've just been using collets to hold my end mills. It's a smaller mill - similar to a G3102. I think the benefit is that I get a little more Z axis space that way (not that I've ever needed it so far). Is there an advantage or reason to use an endmill holder like http://www.use-enco.com/CGI/INSRIT?PMAKA=KE210-0104 instead? I have had an endmill slip out of it's collet a little causing me to cut too deep (it got 'longer' so milling down until I hit the stop caused me to go too deep ruining the work). This only happened once & I could have just not snugged it enough that one time? Or that might be a common drawback of using collets to hold end mills in the spindle. Don't know so that's why I'm asking :)
 
Collets tend to run more true because of the nature of their design. providing they are properly manufactured. End mill holders have a slight amount of clearance built in so the end mill can be inserted into the holder. The force of the set screw pushes the end mill to one side thus inducing a small amount of runout by design. Depending on the quality of the end mill holder this runout can be very small or very large. Both designs work well and each has their advantages/disadvantages.

BTW - To prevent the end mill from pulling down into the work using an end mill holder make sure the end mill is pulled down against the set screw before tightening. This is a trick I learned many years ago during my apprentice training. If the end mill were to move it can only go up.

Hope you find this helpful information.

Tom S
 
I only had a problem with an end mill slipping in a collet once. It was a large 1" end mill. The drawbar needed to be tightened down more. I learned my lesson and never had that problem again. Personally, I've never seen the need for an endmill holder.

Sent from my SPH-L710 using Tapatalk
 
When you flip open the top cover you can see the splines of the spindle, correct? Is there any kind of spindle lock?
 
AlanR said:
When you flip open the top cover you can see the splines of the spindle, correct? Is there any kind of spindle lock?
Click to expand...

I don't *think* there is. Just a big pulley the drawbar goes through.
 
If you are doing some heavy cutting you should use an end mill holder. Often the end mill will push up into the collet or even screw itself right into the work piece. You should never have to over tighten the drawbar to fix a simple problem. If you have a light duty machine, you most likely will never need a end mill holder. If you have something more substantial with 1 1/2+ hp, you should have end mill holders.
 
Personally, I'm a fan of endmill holders and only use collets when I have an oddball size endmill that doesn't fit in any of the holders. I've had endmills slip in collets just as you describe and I've never had that happen when using a holder. Also, I prefer having the extra inch or two of spindle clearance that an endmill holder provides. Finally, I'm not a big fan of tightening the daylights out of a drawbar. Firmly tight is appropriate but, anything more than that is only going to lead to busted knuckles and put undue wear on tear on all things involved.


Ray
 
You can get your tool offset to repeat as well with an end mill holder.
 
Absoutly not being wise, get a Cincinnati and the hell with drawbars.. LOL
edit; I do like Bridgeports too bad we can't melt down a Bridgy and a Cincy pour into one, and have a super mill.........
 
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