Denford Software & Machines

The school where I work has a VMC 1300 mill that has started producing very poor finishes, ie. chatter, ( see attachments ), so while troubleshooting I found some vertical and lateral play when the toolholder is inserted in the spindle. When the pull stud is removed from the toolholder and inserted into the spindle, it can be seated with no lateral or vertical play. Is there a documented procedure about how to go about adjusting the drawbar so that the toolholder is pulled higher and tighter into the spindle ? Any suggestions and direction would be appreciated.

The tool should be pulled up tight in the taper of the spindle so there should be no movement once fitted. Could you remove a pull stud from a toolholder and check it fits in the taper correctly?

All that could cause a tool fitted with the correct pull stud to be loose would be that the springs are not correctly under tension as these pull the stud and the tool into the taper.

Has anyone done any work on the spindle?

I attach the diagram for a VMC 1300 which is much the same. I will also include some photos.

To remove the drawbar there are two nuts at the top that need to be removed VMC/0113 and VMC/0111 then the drawbar will fall clear of the spindle. Note there are four ¼” bearings that will fall out when the drawbar is removed. These should be stuck back in place with grease when refitting.

There are only a couple of things that could cause the tool to be loose:

VMC/0106 the collet that holds the 4 bearings should be fitted so that 4 threads are left visible on the drawbar and then this is locked in place by a grubscrew.

There are 44 springs in the spring stack and these should be fitted in opposite directions to each other. The first locknut (VMC/0111) is screwed down clamping the springs in place so it is 10.5mm below the top of the spindle then locked in place using a grub screw accessed through the hole drilled in the spindle. Then the second one (VMC/0113) is screwed in level with the top of the spindle and again clamped with a grub screw.

Steve, What's the best way to remove the drawbar rocker VMC/073 to get access to the drawbar locknuts? It looks like the rocker pivot has a sort of clip retainer - can I just ping this off?

Just a note to say I serviced my VMC 1300 Pro drawbar using the info supplied and it cured by lose tooling problems. I made a spanner from an old imperial socket to turn the nuts. When replacing the drawbar, not the orientation of the flat on the bar and the indent in the spindle so you can slide the bar up. My Pro has 5 balls in the drawbar.

Is this the same for a Triac?
I’ve got a 1995 Triac with bt35 6pos atc.
I’ve had increasing issues with tool clamping so stripped the drawbar down to clean and ‘decontaminate’ the expected crud and build up of dust etc from machining grp…

Unless they flipped over on removing, there were 3pairs of washers not opposed to each other…. Is this normal?

Is the 10.5mm dimension to top of the lower nut the same for all machines?
I didn’t take any measurements before disassembling…

Thanks

None of the springs should be flipped they should all be fitted oposing each other and the 10.5 should be standard for all.

Thanks for reply Steve

I’ve rebuilt the drawbar mechanism and on the whole, things are better
3 out of 4 holders are clamping fine, but I have one holder that just doesn’t want to pull back and lock out on the spindle taper… despite being used without issue in the past!?!
I’ve swapped pullstuds, with one from the ‘good’ holders… still the same… so I’m a bit baffled by the situation!

I have already moved back/up the front piece of the drawbar by one rotation, so 1.5mm.
My assumption was that this would induce additional clamping pressure on the pullstud/toolholder… but the problem is the same.

I’m wondering if the bevel washers have simply lost a bit of strength over time and the tool holders are just slightly different to each other causing the good/bad within the ones I have…?
Can I exert additional clamping pressure tool holders with the drawbar nut arrangement or bevel washers, without overdoing it and causing an issue with tool release?