Spindle nose re-grind?

[phaxtris]

Story goes...a while back I tossed a center in the spindle...and there was a noticeable "wobble" in the center...so I threw an indicator on the outside and inside tapers, .004" runout!

Yea massive, but not noticable, and doesn't seem to affect accuracy much with the chuck mounted, someone must have turned the backing plate with the runout... whattever

I pulled the spindle this weekend to see if it were bearings or a bent spindle, I've attached a pic of my setup to check the spindle, it may not be .0001" accurate but it is enough to see that the internal and external tapers are definitely running out

The lathe can turn accurate enough parts for my use as is, but it bothers me that i 1 have to turn the face place to have it run true, and 2 I would have to turn the center every time I wanted to use the face plate

So the question is...has anyone ground a spindle nose and Morse taper with a tool rest grinder in situ? Or should I just live with it... skim the face plate and turn a center in pos when I want to run faceplate/center ?

 

[Susquatch]

Can you get a new spindle?

I don't follow why you need to faceoff the face plate each time. Can't it be faced once and then indexed on the spindle so it always goes on the way it came off?

Can you setup a larger female taper right on the face plate instead of using the spindle MT?

Can you make a spindle center adapter that runs true to the spindle and use that instead of the spindle MT?

 

[phaxtris]

Can you get a new spindle?

I don't follow why you need to faceoff the face plate each time. Can't it be faced once and then indexed on the spindle so it always goes on the way it came off?

Can you setup a larger female taper right on the face plate instead of using the spindle MT?

Can you make a spindle center adapter that runs true to the spindle and use that instead of the spindle MT?

i would only need to skim the faceplate once, it has a keyway to register location....this is the reason you cant see the runout with the chucks, they mount to backing plates that are turned while mounted and register in a key way, it would be the center that would need to be cut every time as there would be no way to index it ( if i was using the faceplate with the center)

if i just want to run a center i just do the cut a center in the chuck trick and dog off one of the jaws, no big deal there

the only way im getting a new spindle would probably involve a trip to brazil and learning to speak Portuguese, so thats out

the easiest thing i think would be to skim the face plate and cut the center every time, but that brings up the question, do they make non hardened morse taper centers ? i cant seem to find one


just kinda looking for input on what other people might do....im very tempted to just roll with it how it is, i never even knew it was out until that one day i slammed a center in the spindle for no good reason

 

[YYCHM]

Make your own MT centers and true them up with every use. Do you have a taper attachment?

I guess you could try applying a MT reamer to the current spindle and see if things improve......

 

[phaxtris]

Make your own MT centers and true them up with every use. Do you have a taper attachment?

I guess you could try applying a MT reamer to the current spindle and see if things improve......

i thought about an mt reamer, i dont think it would be hard enough to cut the spindle, and it would probabaly just follow the current taper, i dont know that it would remove the runout

i dont have a taper attachment, i think the compound might have enough travel to make an acceptable taper, i also havent actually tried to cut the center i have.....maybe i should give that a go, what do i have to lose really

 

[PeterT]

A little out of my league here but I really wonder how accurate the spindle tube itself is, which is how you have it supported. If it is slightly banana, then the spindle nose will appear out relative to the rollers. But I think the important runout is the spindle nose once bearing is fixed in the headstock. Did you already establish in the lathe that you have spindle nose runout & that's why the spindle is out now?
Assuming the bearing is still in good shape, is it possible to support on the housing or bearing OD & see if you get the same numbers?

 

[phaxtris]

A little out of my league here but I really wonder how accurate the spindle tube itself is, which is how you have it supported. If it is slightly banana, then the spindle nose will appear out relative to the rollers. But I think the important runout is the spindle nose once bearing is fixed in the headstock. Did you already establish in the lathe that you have spindle nose runout & that's why the spindle is out now?
Assuming the bearing is still in good shape, is it possible to support on the housing or bearing OD & see if you get the same numbers?

Yes, it runs out when installed, I just checked it out of the machine like that as a sanity check, I don't take those numbers as the actual runout numbers, just a confirmation that it wasn't bad bearings

 

[Susquatch]

just kinda looking for input on what other people might do....im very tempted to just roll with it how it is, i never even knew it was out until that one day i slammed a center in the spindle for no good reason

Well that answers my next question which was gunna be "Why do you need a center?"

Ive had a lathe for 40 plus years. I've never used a center in the spindle even once. I don't even have one. My newer lathe has an mt5 taper so that's a honking big taper for a center.

If I need a center, I make one that is chucked not put in the taper, and it's usually just a small piece of bar cut with my compound at 30 degrees to make a 60 degree taper. Since it is cut in a chuck as it will be used, it's always perfectly concentric to my spindle.

Given what you just said, I'd stop worrying about it and just roll with it too.

For that rare time you might actually need one, just get a big bar that is machineable, cut your spindle taper into it using your chuck, flip it, and then make a new 60 each time you use it. An index mark with a punch, or carbide scribe, or even a sharpie might work pretty well too. I frequently use that trick so I can avoid parting off and wasting stock on a bar that is machined full length. It's surprising how well a simple index mark will repeat.

 

[Mcgyver]

I've ground spindle tapers before for collet mounts but don't there is much point for centres imo. With the three jaw chuck mounted, chuck a piece of steel, turn a 60 degree point on it with the compound....I think most machinists do it that way as it eliminates a source of error. The dog is driven by a jaw. The stub in the 3 jaw will be as true to the lathe's axis as the bearings are.

 

[6.5 Fan]

I agree with what Sasquatch said, for the very few times you need a center, machine one in the three jaw.

 

[Susquatch]

I've ground spindle tapers before for collet mounts but don't there is much point for centres imo. With the three jaw chuck mounted, chuck a piece of steel, turn a 60 degree point on it with the compound....I think most machinists do it that way as it eliminates a source of error. The dog is driven by a jaw. The stub in the 3 jaw will be as true to the lathe's axis as the bearings are.

@phaxtris - This is what I recommended above too, but @Mcgyver said it better than I did.

Its also nice to know that this is what most machinists do as I am mostly self taught.

 

[Mcgyver]

@phaxtris - This is what I recommended above too, but @Mcgyver said it better than I did.

Its also nice to know that this is what most machinists do as I am mostly self taught.

lol, me too. I don't mean to sound as if puttng on airs, I'm not a machinist and I can't present a comprehensive and statistically accurate polling around my claim of "most" , but over the years I believe I've heard more guys known to be career machinists saying its how they do so than say they don't do it that way.

I'm sure you'll agree, that once you get onto it, you never think mounting a centre in the spindle.

 

[Former Member]

Well that answers my next question which was gunna be "Why do you need a center?"

Ive had a lathe for 40 plus years. I've never used a center in the spindle even once. I don't even have one. My newer lathe has an mt5 taper so that's a honking big taper for a center.

If I need a center, I make one that is chucked not put in the taper, and it's usually just a small piece of bar cut with my compound at 30 degrees to make a 60 degree taper. Since it is cut in a chuck as it will be used, it's always perfectly concentric to my spindle.

Given what you just said, I'd stop worrying about it and just roll with it too.

For that rare time you might actually need one, just get a big bar that is machineable, cut your spindle taper into it using your chuck, flip it, and then make a new 60 each time you use it. An index mark with a punch, or carbide scribe, or even a sharpie might work pretty well too. I frequently use that trick so I can avoid parting off and wasting stock on a bar that is machined full length. It's surprising how well a simple index mark will repeat.

Depends on how you are doing your work and how you can adjust your work in a lathe.

I've used centers in the spindle on several occasions over 30 years mostly when my spindle is to small for the work to get the best results and there the answer is "turn between centers son"! The second is turning with inducing external stresses from the chuck on the part during turning (this is a whole other discussion).

With modern smaller lathes spindle dimensions have increased so much so that centers are becoming less used, but having the option is great (but time consuming) option.

I bought my new lathe for one reason only, not to use centers as the solution and save about 15-30 mins per piece of prep and setup time, now its just a chuck it and cut it operation.

Now as to your issue of taper correctness, start with your lathe setup first before making alterations this drastic though important if required. There is a whole (heated and very informative ) thread about this. Second test the offending device in the spindle in several orientations to confirm if its the spindle or the device.

Finally if its intrusive enough cut and/or grind away, this is truly how you fix it (there are done good Youtube videos on this).

Remember, check, check, check and check again pause and check again before you cut/grind as worst case could cause you more grief and problems.

 

[phaxtris]

So it sounds like everyone is on the same page, leave it, cut a center in pos when required

That's the way I was leaning, better than chance making it worse

 

[historicalarms]

i thought about an mt reamer, i dont think it would be hard enough to cut the spindle, and it would probabaly just follow the current taper, i dont know that it would remove the runout

i dont have a taper attachment, i think the compound might have enough travel to make an acceptable taper, i also havent actually tried to cut the center i have.....maybe i should give that a go, what do i have to lose really

Im with YYC on a simple new taper pocket manuf would be the most expedient "permanent fix" but i also agree withphaxtris that introducind a stationary reamer into a turning spindle will just produce another wonky pocket....my sugestion would be to take the spindle to another shop that has the capability of turning the reamer into a stationary spindle (line up for square & straight would be crucial).

 

[mickeyf]

The one case that comes to mind in which you might want to put a center directly into the spindle rather than in a chuck is if you have a work piece that is so long that you need that extra few inches of length that the chuck consumes. Rare, but can happen. I wouldn't go out of my way to worry about that until it actually came up, which might be "never".

 

[Susquatch]

The one case that comes to mind in which you might want to put a center directly into the spindle rather than in a chuck is if you have a work piece that is so long that you need that extra few inches of length that the chuck consumes. Rare, but can happen. I wouldn't go out of my way to worry about that until it actually came up, which might be "never".

True, but then what do you attach the drive dog to? LOL!

I'm in the camp that says that @phaxtris will never use it.... LOL!

In my mind, the only time that spindle taper will get used will be for a spindle mounted collet holder or a test bar. The latter is probably a moot case now that we know how wonderful those test bars are.....

 

[phaxtris]

True, but then what do you attach the drive dog to? LOL!

I'm in the camp that says that @phaxtris will never use it.... LOL!

In my mind, the only time that spindle taper will get used will be for a spindle mounted collet holder or a test bar. The latter is probably a moot case now that we know how wonderful those test bars are.....

You would drive the dog off the faceplate, it mounts flush to the spindle nose, err flush with the spindle nose

 

[Susquatch]

You would drive the dog off the faceplate, it mounts flush to the spindle nose, err flush with the spindle nose

I meant without the faceplate....

We already talked about the faceplate method before so I assumed this is without that and hence my question....

 

[phaxtris]

I meant without the faceplate....

We already talked about the faceplate method before so I assumed this is without that and hence my question....

Without the faceplate method loses you the 6-8" for the chuck, that's the point of the center in the spindle...center in the spindle dog driven from the faceplate