O/T Problems with Power Drawbars

[Phil Orenstein]

Any ideas? The CNC Bridgeport kneemill that I am working on has a consistent power drawbar problem (among many others ) Larger tools cutting a 4130 tool steel job vibrated too much even on slow feeds and speeds, and would reverse spin out of the spindle, causing crashes, damage to the tool and the part. This happened 3 times until finally the tool adapter ears broke off. I checked the drawbar and it was not too worn at the bottom. Anyone else expereince this? What else can I do to prevent the spin outs?

 

Thanks buddies for the help!

Phil

[crazy^millman]

Phil I would contact a service person and have them check the pressure pull on the pull stud. I would also make sure you got the right pull stud on it as well. I have had the oppsite trouble with Facemills and that is them sticking after using them for hours at a time on HRS plate. I might also check the runout on the spindle insde the taper and see what it is reading. I had a Mazak that gave me nothing but fits would not rigid tap and a host of other problems. I finally after 7 servcie calls got the guy to do that and it was out .0017 where as they said .0004 was excessive so guess what after 7 months they finally put me a new spindle in and that machine is now 4 years old and I talked to the guys the others day and the machine is still running strong.

 

Good luck.

[Teh Bear without Brains kinda idiot]

Phil!

Once I had similar problem

It can be very dangerous ,even mortal (GSYFC).

It was toolholder clamping mechanism problem ,A tool was not clamped tight .

We found that in this case most dangerous are the regular end mills with flute spiral 30-45 degrees.

they were pulling tool out of the spindel ,like corkscrew .

While insert mills tend to pull toward spindel and much safer .

But anyway ,no-no for big rpm ,or this bloody thing (toolholder +tool weight 3-5 kilograms at least ) in big rpm can turn to APDS tank shell.

I once got from this "sitivation " by pure luck .

The holder whistled close to my head by couple of inches and smashed into the column .

Be cautious and check all over ,the human and nonhuman life far more prrecious ,then a bit of $$

 

Regard this

[Phil Orenstein]

Thanks a lot guys! My boss says we don't need to do any more heavy milling on that machine. Just light duty aluminum jobs.

 

Phil

[Teh Bear without Brains kinda idiot]

Phil !

 

In your place I`d better repair it .

In my case it happened in alluminium .

I was aware of the problem ,just forgot to change S5500 for a reasonable in this case S1200 .

If somone will be dead because of it , your boss will be guilty and your company will pay a lot of $$$$$$ not to mention the moral aspect of the matter .

 

Teh scared bear

[Keith Graydon]

I'd still check the taper