R8 chuck not fitting the taper?

[zaebis]

Folks,

I have a machine (one of those CNC converts) that I purchased recently with R8 taper. All the R8 tooling that I have works fine, I can pop it in and tighten the drawbar. Except one R8 chuck - ER20 collet holder that I really need but it doesnt fit the taper. It slides almost all the way in, I can feel that key is in the keyway but then it stops against something short about 1/2 inch of being fully seated so I cant grab it with a drawbar to tighten.

When I compare this chuck visually with all others (that work) there is no difference!!! I calipered all the sizes and the only slight difference is that the keyway is slightly narrower on the problematic chuck. Anyone experienced anything like that? The chuck is made in Poland and has a good quality finish on it.

[One of Many]

The depth of the keyway may be a bit shallow. You could back out the key in the spindle a tad. The lower bearing cap would need to be removed to gain access to the setscrew that retains the key.

Either that or carefully recut the keyway in the collet.

DC

[zaebis]

Originally Posted by One of Many The depth of the keyway may be a bit shallow. You could back out the key in the spindle a tad. The lower bearing cap would need to be removed to gain access to the setscrew that retains the key. Either that or carefully recut the keyway in the collet. DC

The depth? It is exactly as the one from the working chucks. Its width is however slightly less (by .005). Also when it doesnt fit in it stops decisively and against something solid. I will double check the depth today though.

[littlerob]

I would just take the key out, once the collet is tight it's going nowhere unless for whatever reason you are using L.H. tooling. I always take the key out with an R8 collet. JMO

Robert

[mactec54]

Hi littlerob

That is not what you tell someone to do (remove the key) I know a lot of unskilled people do this only to reck/damage the spindle over time

[One of Many]

Originally Posted by zaebis The depth? It is exactly as the one from the working chucks. Its width is however slightly less (by .005). Also when it doesnt fit in it stops decisively and against something solid. I will double check the depth today though.

One way to find out if it is the key way fit is to remove the key and try it without. The key isn't required to drive the collet, it is primarily intended to tighten the collet.

I have found where the upper diameter edge of an import R8 holder had been swelled in one spot from a drop to the floor. It didn't take much, but enough to prevent it seating.

DC

[littlerob]

Originally Posted by mactec54 Hi littlerob That is not what you tell someone to do (remove the key) I know a lot of unskilled people do this only to reck/damage the spindle over time

How is it going to damage the spindle? What spindle reckage/damage could possibly occur over time? As DC said it isn't there to drive the collet it is just a guide for tightening it.

[Geof]

Originally Posted by mactec54 Hi littlerob That is not what you tell someone to do (remove the key) I know a lot of unskilled people do this only to reck/damage the spindle over time

Not only unskilled, sometimes very skilled; the key hasn't been present in my original manual mill for about twenty years and it works fine. As both littlerob and DC say it is only there to stop the collet turning while you tighten the drawbolt.

[One of Many]

Originally Posted by Geof Not only unskilled, sometimes very skilled; the key hasn't been present in my original manual mill for about twenty years and it works fine. As both littlerob and DC say it is only there to stop the collet turning while you tighten the drawbolt.

Spinning a Collet isn't as risky. With or without a key, I've seen the results of fly cutters and shell mills spin and neither ends pretty when conflicting with a solid object. When it does occur, the only difference between skilled and unskilled operators is; one knows how to cover it up and the other can just play dumb not knowing what all happened or why!

DC

[mactec54]

Hi Guys

There is more to this key thing than most are aware of the key is not there just to hold the collet while you do it up

By removing the key in a R8 you leave a hole in the inside of the spindle ( in most) which can & will let metal chips & junk into the spindle bearings (on some) not good short life for the spindle bearings at $300 a set

The key is there also to hold the collet from turning when you undo it if you get a tight thread I would like to see the mess you make of the collet/drawbar etc trying to get it out without a key

What would a manufacture go to the trouble to put a key in a spindle if you don't need it
may be Geof has the answer 20 years without a key????

Machining centre's have key's some have ( 1 ) some have ( 2 ) to locate the tool holder
& to stop it from being able to turn in the spindle while cutting

Another reason a key is there is so you put your collet/toolholder always in the same location in the spindle if your collet or toolholder get damaged or a chip gets on it there will only be damage in the spindle or collet/ toolholder in one place without a key you will get damage were ever the collet or toolholder is placed in the spindle it does not take long for a spindle to be of no use once it is damaged like this


I was at one time regrinding spindles 4 to 6 a week because of this kind of damage mostly because people new better than the manufactures & removed the key

[mc-motorsports]

Originally Posted by mactec54 Hi Guys There is more to this key thing than most are aware of the key is not there just to hold the collet while you do it up By removing the key in a R8 you leave a hole in the inside of the spindle ( in most) which can & will let metal chips & junk into the spindle bearings (on some) not good short life for the spindle bearings at $300 a set

That is a valid point.

Originally Posted by mactec54 The key is there also to hold the collet from turning when you undo it if you get a tight thread I would like to see the mess you make of the collet/drawbar etc trying to get it out without a key

I guess a little finesse is required. I'm not going to say it's impossible to screw something up, I'll only say I've never had a problem.

Originally Posted by mactec54 What would a manufacture go to the trouble to put a key in a spindle if you don't need it may be Geof has the answer 20 years without a key????

I think he will be ok.

Originally Posted by mactec54 Machining centre's have key's some have ( 1 ) some have ( 2 ) to locate the tool holder & to stop it from being able to turn in the spindle while cutting

We're probably talking about a 2hp machine, and as you know, the spindle taper is what is holding the tool, otherwise the taper contact patch would not be so critical.

Originally Posted by mactec54 Another reason a key is there is so you put your collet/toolholder always in the same location in the spindle if your collet or toolholder get damaged or a chip gets on it there will only be damage in the spindle or collet/ toolholder in one place without a key you will get damage were ever the collet or toolholder is placed in the spindle it does not take long for a spindle to be of no use once it is damaged like this

I have yet to see a R8 automatic tool changer, hence the operator input upon manual tool changes, I think you learn to keep precision surfaces clean and well kept on the fist day of your apprentiship, trade schooling, or on the job training, no?

Originally Posted by mactec54 I was at one time regrinding spindles 4 to 6 a week because of this kind of damage mostly because people new better than the manufactures & removed the key

I rebuilt spindles for 9 years, I saw some of the dumbest mistakes ever made, some of them, I couldn't imagine watching happen. As much as I would not encourage removing the locating key from a R8 spindle, it's not the end of the world.

I have 2 knee mills without the key, bought them that way, never worried about it. They are both in use every day, one for 2 years, the other for 5 years, no problems with the spindles.

MC

[davereagan]

You could have massaged the keyway in the problem collet with a die grinder in less time than it took to stroke down this post.