Any machinists on here?

[JxxxOxxxE]

I'm sure we've got some...

I've got a couple questions regarding truing a lathe spindle and wondered if we had anyone with the knowledge...Someone that has used or owns a tool post grinder would be great....

 

[CBCollier]

We have a tool post grinder in the shop. Not my forte, but shoot me a question, I would be glad to get it answered by me or the other guys in the shop.

 

[JxxxOxxxE]

We have a tool post grinder in the shop. Not my forte, but shoot me a question, I would be glad to get it answered by me or the other guys in the shop.

Basically I acquired a free lathe a couple years ago. I've done some repairs to it and used it off and on for random projects that had no real tolerances. I now have the need for some real accuracy.

I replaced the spindle bearings in it as they were pitted very bad which showed when trying to finish a part.


What has happened is that someone sometime before me tried to true the D1-6 spindle and nose taper up with the old worn out bearings...This has made the runout on the chuck quite bad


You can tell in these 2 pics that someone has attempted to bevel the front edge of the nose taper rather crudely. Its completely uneven and I could probably be more consistent with a electric grinder...

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Here are 2 short videos showing the measurements

http://www.youtube.com/watch?v=FwIudpVMCDg

http://www.youtube.com/watch?v=mHHj32RWYbg


From some reading on some of the national machinist sites, it seems like I need the use of a tool post grinder to grind the spindle face back true, and re grind the taper to the correct dimensions...I'm afraid getting the taper correct may be above my current skill level...

 

[Shadowrider]

Wow man that spindle's whacked.

Do you have a taper attachment on your lathe? If not you are going to need more than a tool post grinder otherwise you can't do the taper. Form grinding it won't get you any kind of accuracy.

We always had someone come in and regrind the tapered spindles on our mills. You can get it close enough for home projects with a taper attachment but it's not going to be easy and you will need to find the taper gages somewhere. Basically you grind the tapers 1st to cleanup and then regrind the faces to fit.

 

[CBCollier]

Maybe I am just not seeing it, but the runnout you are showing is on the face of chuck or is the chuck removed? If that is the chuck, is the damage done to the chuck or the actual spindle of the lathe. If it is actually in the spindle like you say, then boy, you do have a mess on your hands. When you said tool post grinder, I was under the impression you where referring to a grinder used to regrind tools.

 

[JxxxOxxxE]

Wow man that spindle's whacked.

Do you have a taper attachment on your lathe? If not you are going to need more than a tool post grinder otherwise you can't do the taper. Form grinding it won't get you any kind of accuracy.

We always had someone come in and regrind the tapered spindles on our mills. You can get it close enough for home projects with a taper attachment but it's not going to be easy and you will need to find the taper gages somewhere. Basically you grind the tapers 1st to cleanup and then regrind the faces to fit.

Definitely...whacked....LoL...

I do believe I have the taper attachment, although I've never messed with it...And being as novice as I am, I am not sure if its all there or not...

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I believe the taper needs to be 7* 7' 30" as referenced here: http://www.lathes.co.uk/latheparts/page12.html


Do you recall any of the people/companies that were used to regrind the spindles? I've yet to find anyone in the state that does it. A new spindle is $1500 from the manufacturer, although before I go that route I will pull the spindle and send it out to have it looked at first...

Maybe I am just not seeing it, but the runnout you are showing is on the face of chuck or is the chuck removed? If that is the chuck, is the damage done to the chuck or the actual spindle of the lathe. If it is actually in the spindle like you say, then boy, you do have a mess on your hands. When you said tool post grinder, I was under the impression you where referring to a grinder used to regrind tools.

The chuck is removed. Thats the face of the spindle.

Here's the back of the chuck

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Here's a front shot of the spindle

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Depending on the type of tool post grinder your envisioning, thats what is supposedly used...

 

[Shadowrider]

Yep that be the taper attachment. You are probably right on the angle, that sounds right from what I remember. You might just be able to be turn it in place. You still got to come up with a gage and some prussian blue tho.

But honestly, I would pull the spindle and send it out if you are able. It is possible to do it with your taper attachment but it would be an incredible PITA to do and that's provided that you can even find a master gage to use. If you can send it out and it is in fact re-workable that would definitely be your best route. Even replacing it with a new one would be better than the guy we used. He was out of state back east somewhere and his travel costs had to be covered in addition to his fee. It took him about 4 hours to do a CAT5 spindle on a CNC mill, so we always had him come if we needed more than one done. I have no idea of anyone local that does this.

 

[romanleader]

Curious what the run out is on the face and o.d.

 

[JxxxOxxxE]

My only concern with pulling the spindle out and sending it off is that it seems to me that I'd get a better alignment/concentricty if it were ground/trued in its own bearings...maybe that's not the case though...

Curious what the run out is on the face and o.d.

This video http://www.youtube.com/watch?v=FwIudpVMCDg shows it around .006"

I took a reading on the OD, but figured it wasn't really relevant as its not a mating surface...I don't remember what it was...

 

[Shadowrider]

As long as they indicate both the front AND rear bearing surfaces in dead nuts it will work. I guarantee you the factory doesn't grind the spindle surfaces on each individual machine after assembly. Besides if you are doing really close tolerance work you will want to true your chuck jaws occasionally anyway and that does exactly what you are talking about.