[thomasz]

Hi!

We have to rebuild the spindle in our 4020HT (10.000 grease).

To chance the bearings and grind the taper isn't the problem,
we have a partner company that does it for us.

Problem is if the taper is grinded, the face have to grind a lillte too.
Some BT40-holder would not seat in the tape completly.

Unfortunately you can not unscrew the pushers (drive dogs) on the front of the spindle.
How to take away some material?

Thomas

[txcncman]

When you say pushers, I assume you mean what I call drive dogs. Since I have never done this rebuild, please explain why you cannot unscrew them.

[thomasz]

Hi!

The two drive dogs - you are right.

You can't unscrew them - see pic.

Thomas

[HuFlungDung]

I don't think you'd have much choice except to grind the face. You'd need to set up a vertical grinding spindle on the table of your machine, with a cup style wheel, orient and lock the spindle so the lugs are aligned with the table travel, and write a little program to surface grind the spindle face on each side of the lugs.

[txcncman]

Thanks. I would recommend not grinding in place unless you are 100% confident of the machine alignment.

[thomasz]

the spindel ist already build out from machine

[denmar]

Don't see why to regrind the face, it's got nothing to do with the rotor taper.

[txcncman]

Don't see why to regrind the face, it's got nothing to do with the rotor taper.

My understanding is that they need/want to regrind the taper. They have concern when the taper is reground, the tool holder flange will interfere with the spindle face. They could have the tool holder flanges reground. But then anytime a new tool holder was purchased, it would have to be reground also. Since they will already have the spindle at a regrinding facility, it just makes since to take care of everything at once. I personally do not think they should have to grind enough from the spindle taper to cause tool holder flange interference. This could all be calculated out. I do not know if they have done that much homework or not.

[txcncman]

If my calculation is correct, and they grind 0.010 per side on the spindle taper, the flange of the tool holder will be moved 0.0693. I do not know if this is enough to cause interference between spindle face and flange.

[denmar]

If you look closer, the tool holder flange seats 0.150 below the face.

[txcncman]

If you look closer, the tool holder flange seats 0.150 below the face.

I do not understand your point. Are you trying to say that since the flange to spindle face clearance is designed to be 0.150 that there is no need to regrind the spindle face?

[thomasz]

okay - i try to explain:

the space between face of the spindle and flange from one toolholder
is now 0,7mm (0,027") - there are other toolholders with little more space
but 0,7mm are the smallest

if we grind now the taper a little bit, the tool will get deeper in the
spindle of course

but if the tool get more than 0,7mm in the spindle we have a problem
because the toolholder will not sit in the tape exactly

If you look closer, the tool holder flange seats 0.150 below the face.

wow - if so, we have another problem - a look in a cataloge say BT40: 2mm (0,08") - hmm

[txcncman]

@thomas - I think you should carry on with grinding the face. I do not think denmar understands what you are attempting to do.