Thread: Headstock Spindle Advice Please

In picture 2 those bearings look pretty badly scuffed.

I would replace them.

Rob

Hi there,

I can't advise on what you should do but I can advise on the removal of the bearings since I have done that some time back. The front taper bearings are a pain to remove because of the cover plate and spindle nose but I managed to fit 2 sufficiently thick pieces of material between the bearing and spindle nose, one either side and then CAREFULLY pressed it out on a press. I think that carefully pressing them out is a lot less likely to affect any accuracy or cause damage than hitting them out with a soft dolley and hammer.

That front roller bearing looks like a typical Chinese bearing that has had crap passed through it. Mine were the same, mainly from the casting sand that got constantly passed through them. Mine were bad enough to effect the quality of the finish on anything I turned. Have you had this problem with those bearings? Maybe yours are not that bad, sometimes the camera can make things look worse than they are! What does the outer race look like?


Cheers,

Simon

I would go for the seal if you can. Good thinking on the indexing slots.

Dave

Yeah - I'm not happy with the look of the outer race either. My 'press' (also made of recycled materials) is limited to about 5T - I will give it a try, but if I fit new (quality) bearings, then it won't matter too much if I drive it off.

Yes Simon, I would say it's been pretty difficult to get a really good finish. However, I have not seen any evidence of moulding sand - yet.

The seal will be an interesting exercise because I will need to put everything back together (with a temp plastic flange) while I turn up the flange to take a 'real' seal. ... Then pull the spindle out again to fit the reworked flange!

I need someone nearby to machine the flange out while I'm 'latheless'.

Dave & Ewan might be interested to see my planned index slots (V's) IAW this chart that divides the circumference into 3s, 4s, 5s, 6s, 7s & 10s.
HSIndexMarks.jpg
I will make a stop attached to the flange with a M8 to screw down onto notches on the spindle plate.
Why 7? Some countersinks have 7 cutting edges (to sharpen) and some key-mills have 10 teeth. Yes, I know PDW will say 'just buy new ones', but where is the challenge in THAT?

Will show results soon, Regards Daryl

Lathes do not have lip seals on them, for the reason they generate considerable amounts of heat, this then expands the spindle increasing preload of the bearings..

They run labyrinth seals, I guess this is what yours would have as they seem to be industry standard at least on manual machines...

Originally Posted by DarBee

I will make a stop attached to the flange with a M8 to screw down onto notches on the spindle plate.
Why 7? Some countersinks have 7 cutting edges (to sharpen) and some key-mills have 10 teeth. Yes, I know PDW will say 'just buy new ones', but where is the challenge in THAT?

Will show results soon, Regards Daryl

Nah I'd say get a dividing head or simple indexing head..... buy or build, either. Does what you want and a lot more that sooner or later you *will* want as well.

Plenty of plans out there, a good machining project and a useful tool at the end of it.

Though if you do a lot of cutter sharpening you're going to need a tool & cutter grinder. And so the machine tool collection grows.

PDW

DarBee, sometimes when you remove metal from a precision machined component it can change the stresses and then that component may no longer be precise.
Why don't you think about making a new backing plate for your chuck incorporating the indexing plate ?

Hi Daryl

Originally Posted by DarBee

then it won't matter too much if I drive it off.

Well unless you bend/ding the spindle that is.

I'm with Shed, making an add on part also means you can screw up and not worry

As far as sealing the spindle goes. You're worried about grinding grit/dust? One idea I've been putting a little thought into is feeding compressed air into the heatstock. Only way out is through the bearings. This should stop anything coming in and I wouldnt have thought you need to use much air. Still I dont know as I've been looking at air filters, but I'm not even sure it really needed(above what I use for spray painting). Maybe a little fuel filter just before the headstock for luck lol

Whats the diameter of the part you what wo cut indexing grooves? Are you sure you have enough space between the grooves?


Stuart

Evening All,
Well I am back with a new set of bearings - best quality japanese ones that I could find. Looking now at the sage advice above, of course I need to change tack a little bit.

The reason I needed the flange OFF was to increase the size of the chuck bolt access zone in the flange - here it is nearly done;
P5310775.jpg

It was a bit of fun removing the bearing using my 35 YO H.R. Mfrd press (Heath Robinson brand - AKA Daryl), but as always, It's never failed me yet. Well .. it did fail a few years ago when the jack seal failed after I whacked the top bar with a hefty knockometer!!
P5310773.jpg

As some of you have described, the flange contains a labyrinth seal - not very effective to my way of thinking. However, I hear where you are all coming from (in the words of some one famous). While at the bearing shop today, he found an O ring that fitted into the labyrinth groove. I'm wondering if it wouldn't cause a heating problem after the 1st hour of use, if well greased. I'd think the risk of potential (rubber) contamination would be low.
P5310774.jpg

Other Issues
Upon your sage advice, (thanks Shed), I'll make a separate plate for indexing. For Stuart, the DIA is about 110mm. The 3rd row of the table gives me an idea of the deg/distance between those grooves that will be close together.

Pre-Load (another chance to advise me again please!)
How should I determine how much pre-load should be on the bearings? I can see a bit of a problem here because the notched nut (back of spindle) was pretty tight to get off, so there isn't going to be much 'feel' getting it back on.

Old Bearings (HRB brand)
Some of you may be interested to know that the bearing man pointed out to me today that the back bearing was marked as a 'Precision' bearing (.../P5), but the nose bearing isn't so marked. Notwithstanding, he also mentioned that they have never heard of HRB EVER making P bearings!

As usual, many thanks for your replies - looking forward to some more now.

Regards, Daryl

PS: What about young Alak - brings back some school days memories doesn't it.

Originally Posted by DarBee

As some of you have described, the flange contains a labyrinth seal - not very effective to my way of thinking. However, I hear where you are all coming from (in the words of some one famous). While at the bearing shop today, he found an O ring that fitted into the labyrinth groove. I'm wondering if it wouldn't cause a heating problem after the 1st hour of use, if well greased. I'd think the risk of potential (rubber) contamination would be low.

I'm not sure where you are heading here DarBee ?
O rings are a static type seal, sometimes they are used on pump plungers and they are also used for nuttin a ram, but I cannot remember seeing one used as a seal on a spinning shaft.
If you put an O ring around your lathe spindle it is going want expand when the revs start to get up a bit, it will not last long.
You really need to ascertain if dirt got in to the bearing ? Was it a faulty brg ? People have run these lathes for a long time without having to modify the labyrinth ?

shed

Ha! The ol' precision Chinese bearing trick!

Well, my lathe originally had precision front and rear. P5 front and P6 rear. With the two bearings, it's the play or eccentricity or lack of precision in the front bearing that will show up more in your finish than the rear. In the end, I found it difficult to find P6 and also many here have said that P6 is not really a precision bearing, either way I decided to put in P5 front and rear.

They were not easy to come by, one came from the U.S. and the other from the U.K. but they were less than half the cost landed from anyone here! Many people just put in standard (but good quality) bearings and report good results. I wondered if in reality if a good quality (SKF, NTN, Nachi, etc) bearing are still better than any "precision" Chinese bearing and certainly keep the precision over a longer period.

Now for preload. When I was replacing mine, a search on preload for such came up with many different "tried and tested" methods that people had. Probably the most common method was to nip up the nut until no noticable end play was present, then check for movement with a dial indicator on the spindle. (Don't forget, there will be a small amount of load on the nut even before the endplay has been taken up as the nut pushes the bearing onto the spindle shaft. Also, if backing off the nut, the preload will not be reduced until you give it a knock with a mallet.) Now, run the lathe at the lowest speed setting for about 15 min and check the temp with your hand. They shouldn't get too hot to touch but should get warm. If there is noticeable play then nip up a bit more and re-test.

Once you are happy with the results, run the lathe in all speeds for about 20 mins each, starting at the lowest speed, working up to the fastest. Check the bearing temps again, check spindle play again.

Some people mention chucking up a 12" bar in the lathe and measure with a dial indicator the deflection at the chuck while levering the bar but I'm not sure about 2 things, (1) how much force you use and (2) what is acceptable result on the DI.

Also, make sure your bearings a really clean when installing. I triple washed the bearing and cones and installed with examination gloves and squirted them with clean oil before running the lathe as initially they would start up dry otherwise. Probably a bit OTT but hey I know I did a good job and shouldn't ever have to replace them.

Other, more experienced people may shoot me down with this so I'll be interested to see what other have to say.....

Simon

Originally Posted by shedhappens

I'm not sure where you are heading here DarBee ?
O rings are a static type seal, sometimes they are used on pump plungers and they are also used for nuttin a ram, but I cannot remember seeing one used as a seal on a spinning shaft.
If you put an O ring around your lathe spindle it is going want expand when the revs start to get up a bit, it will not last long.
You really need to ascertain if dirt got in to the bearing ? Was it a faulty brg ? People have run these lathes for a long time without having to modify the labyrinth ?

shed

I agree. Have you looked inside the headstock. Is the oil very clean, no sludge, no sand or grit? Most contaminants that manage to get past the labyrinth will only get through the bearing once, before settling on the bottom in the headstock. That's if they enter at the top, at the bottom, they miss the bearing.

Your bearings look like they have been damaged by continued abuse by numerous contaminants over a period of time. They looked like mine did.

There is not a huge amount of clearance between the spindle and labyrinth, I wouldn't think too much would get in there. I have machined CI and yet in has never managed to find it's way in the headstock.

I would clean your headstock out thoroughly, flushing with kero, replace the oil, do some more work on your lathe. Then after a few hours of turning, open your headstock up to look and see if anything has got in. If it's still clean then don't fix it cause it aint broke!

Cheers,

Simon

Thanks Simon & Shed. Looking at another post here a couple of weeks ago had also convinced me to ensure the entire headstock should be thoroughly cleaned out. The opportunity has now arrived.

The inside of the head does look clean - but I'd prefer to chuck the oriental oil anyway.

Thanks Simon for the detailed pre-load info - very useful. Not quite the same as changing the trailer bearings .

I will leave the labyrinth seal alone as well - but might try the O ring on the outside of the spindle - up close to the flange - that should act as a slinger if any crud gets on it. I can always cut it off if ineffective.

Avagoodweekend, Daryl

It's interesting reading some aspects of this thread.

The assumption that a lipped seal will cause enough friction to heat up a spindle is apparently a big worry, but it's nothing compared to heat build up from pre-loaded roller bearings, which is apparently OK.

I'm just a little surprised that a tiny lip edge on a seal could be such a major heat source - I find that hard to believe, as it would just burn itself away in a short time without oil and if lubricated spin harmlessly with oil.

I agree that an "O" ring is not generally used for a high speed spindle.

Although I generally dislike quotes from Wikipedia as it's less than accurate on a lot of stuff, I think it touches on the main points in this case:

Labyrinth seal - Wikipedia, the free encyclopedia

Labyrinth seals (or oil slingers) have been used for a long time as an alternative to a felt or neoprene seal in a variety of mechanical devices, but I have serious reservations that it's a heat related choice.

In regard to preloading roller bearings, on my lathe the tension is correct if it takes the chuck and spindle 1.5 turns to stop when spun by hand, with the change gears and drive system disconnected.

Cheers

Rob