Orden TC grinder

[Bryan]

Genemens. I've pulled the spindle out of my grinder, hoping to find out where the .1mm (.004") runout is coming from. One of the bearings stayed in the housing and one came out with the shaft. The shoulder on the shaft is the same diameter as the inner race. How do I remove this bearing? These are "super precision" ABEC-7 bearings that need to be reused if at all possible, so Bubba can sit this one out thanks. :) (Though his paw prints are all over the machine already.)

I've left the thread title vague in case I want to post other stuff about this machine.

[scottyd]

Have you tried looking up the bearing and seeing how much interferance it is designed to be mounted with? That way you can get an idea of the force thats holding it in place. That said, I reckon youve got a snowflakes chance of getting it off and not damaging the bearing. Is the bearing second hand? It might not be at ABEC7 specs anymore anyway.

[.RC.]

hmmm would dipping the shaft end in dry ice help? If you can get dry ice that is... With a hair dryer on the bearing...

Also it is a mm Fafnir, so a deep groove and not an angular contact....

[Michael G]

The only thing I can think of is a 3 jaw bearing puller on the outer race, very gently and as soon as there is a gap between shoulder and bearing that is big enough, slip in something that will pull on the inner ring.

Michael

[Bryan]

Have you tried looking up the bearing and seeing how much interferance it is designed to be mounted with? That way you can get an idea of the force thats holding it in place. That said, I reckon youve got a snowflakes chance of getting it off and not damaging the bearing. Is the bearing second hand? It might not be at ABEC7 specs anymore anyway.

It is very second hand, and there's every chance the only spec it meets is PR (pretty ropey). But until I know that I will proceed with caution. Good idea on the fit, will have a dig..... Ok, if I'm reading the table right it could have up to about 6 microns of interference. How much force would that be? My gut feeling is any interference could be enough to do damage.


hmmm would dipping the shaft end in dry ice help? If you can get dry ice that is... With a hair dryer on the bearing...

Also it is a mm Fafnir, so a deep groove and not an angular contact....

Interesting. The documentation I found was confusing in that this bearing doesn't seem to conform to their nomenclature. It has the WI which means angular contact, but not the prefix number which gives the contact angle. See attached. They do appear to be AC because one shoulder is higher than the other. Must be way obsolete.

Not sure how well heat would transfer through the balls to the inner race. Any chance of cooking the cage? Looks like phenolic. That's pretty heat-proof right?


The only thing I can think of is a 3 jaw bearing puller on the outer race, very gently and as soon as there is a gap between shoulder and bearing that is big enough, slip in something that will pull on the inner ring.

Michael

Maybe in combination with thermal persuasion.... ?

[pipeclay]

Looking at the picture it appears to be a through bore,why cant you just knock the other bearing out with a drift.

[Michael G]

Looking at the picture it appears to be a through bore,why cant you just knock the other bearing out with a drift.

It's the bearing on the shaft that is the problem, not the bearing in the bore.

Michael

[Bryan]

Would this type of puller be applicable? I think one side is flat, and that would go against the bearing?

Pipeclay, the makers have provided holes for punches to extract that bearing from the housing, so that shouldn't be a problem. As MG says the shaft is the issue. And I believe it's Not Done to apply force through balls.

[scottyd]

It is very second hand, and there's every chance the only spec it meets is PR (pretty ropey). But until I know that I will proceed with caution. Good idea on the fit, will have a dig..... Ok, if I'm reading the table right it could have up to about 6 microns of interference. How much force would that be? My gut feeling is any interference could be enough to do damage.

Bearings can be designed to be put into place with interferance fits or with certain loads placed upon them. This is why preloading the bearings in a car's wheel bearing is so important, that last final squish is what pushes or stretches the bearing components into their intended fit. The designer of your grinder would have specified the bearing, then specified the shaft interferance to suit the manufacturers recommendations, that way the bearing is spot on when it goes on the shaft.

I dont know how much force 6 microns will yeild, but ive pushed one on that had 4 microns and it required a press. I would say yours is tight enough that a hammer will not do, but others may know more conclusively than I.

If the bearing is knackered, just get it off and replace it. No point going to all this trouble just to look after a rooted bearing. Id replace it and contemplate a lower spec bearing, but it depends on your needs. Having seen the for sale thread where you picked this machine up, Id hardly suggest you can justify the mega price of an ABEC 7 spec replacement...Id love to know the price, I bet its really funny.

[Oldneweng]

Mill away sections of the shoulder to enable access for a pin punch?

Dean

[Michael G]

Would this type of puller be applicable? I think one side is flat, and that would go against the bearing?


That's the sort of puller I was thinking you needed once you can get it in. I think the least damage will be done to the bearing if steady pressure is applied.


Mill away sections of the shoulder to enable access for a pin punch?

Dean, Bryan is in a Shaper only household. While that thought is attractive as soon as you remove some material you also run the risk of throwing the shaft out of balance. While I would not dismiss it out of hand I would be approaching with caution.

Michael

[Stustoys]

Would I be completely crazy to think that the dynamic load a bearing can take is higher than its static load.. so if you were going to pull on the outer race would it make any difference to make it such that the shaft turning?

(I have an excuse if this idea is sillier than my norm. I'm on the sick list lol)

Stuart

[.RC.]

Interesting. The documentation I found was confusing in that this bearing doesn't seem to conform to their nomenclature. It has the WI which means angular contact, but not the prefix number which gives the contact angle. See attached. They do appear to be AC because one shoulder is higher than the other. Must be way obsolete.







Should not trust my memory should I.... I saw the 2 missing and had some brain thought that 2 meant angular contact..

[Michael G]

This the page for the SKF version of that bearing (tolerances to one side). The static load is around the 2 tonne mark. Now without being a bearing expert (far from it) I would suggest that provided the force to remove it did not exceed this (and no shocks were involved) it should not damage the bearing. (Static load is in a radial direction and the removal force is axial but as it is angular contact will that really make a difference?)

296666

Michael

[pipeclay]

It shouldn't be that tight on the shaft,just push or knock it off,if the problem is in that bearing then it doesn't matter.

[Bryan]

Lots of sensible ideas coming out - much clearer than my own. (Does that mean I've outsourced my brain?)

Scottyd, the price was lower than a pair of those bearings. I'm just going by (US) ebay where they seem to run around $200-250 a pair. I'm being tight because the machine has other issues and I'm not sure how useful it's going to be. A lower spec seems a sensible option.

<sounds of digestion>

OK here's a plan:

Gently apply a 3 jaw puller. If it comes off easy great, if not:
Try harder to assess condition. If NFG, replacement pair needed, gloves off. If good:
Buy spreader. Try to chamfer shoulder to suit.

[Stustoys]

How about you pull the other bearing halfway out and then use the head, 4 bolts, 4 spacers and a large center bolt as a pusher?
(or pull from the other end depending on what the shaft looks like?)

Someone else can work out what torque on what sized bolt = 2 tons :D

Stuart

[gallegos]

Axial capacity of ball bearings is usually a small fraction of radial capacity... I think pulling the outer race will defintely stuff it.

[scottyd]

Would I be completely crazy to think that the dynamic load a bearing can take is higher than its static load.. so if you were going to pull on the outer race would it make any difference to make it such that the shaft turning?

(I have an excuse if this idea is sillier than my norm. I'm on the sick list lol)

Stuart

He would need to buy a bearing bigger than the one he is trying to remove to be able to apply more load with it. If he had spare bearings of a larger load rating handy and some sort of way to mount it, then it would work. Given most of us dont have huge bearings just lying around. Also, your assumption is that the bearing's fit on that shaft will require less force than its max dynamic load, which is unknown at this point.



Axial capacity of ball bearings is usually a small fraction of radial capacity... I think pulling the outer race will defintely stuff it.

Pretty well what I was thinking too. Unless there is a way to push the inner race only, its all over bar the shouting for that bearing unless it comes off with less than its rated max load.

[Michael G]

Slight diversion here -
I bought a pair of SKF angular contact bearings last week because of the noises in my head - these were 206 size and cost $35 each. However, while picking them up I asked the bearing guys how to tell if an angular contact bearing is stuffed. The answer was basically you can't as once it is out of it's mount it is that sloppy that you don't know what is wear and what is normal clearance.

Gallegos, I'd agree with you for a deep groove bearing but for angular contact bearings I'm not so sure. If pulled in the direction that the preload is applied in I would have thought there should be enough metal there that they can cope with more than a DG. How much more is another question of course...

Michael

[pipeclay]

If the bearings are to be reused if possible cant you check the bearing on the shaft as is without needing to remove it?

[eskimo]

hmmm would dipping the shaft end in dry ice help? If you can get dry ice that is... With a hair dryer on the bearing...



many years ago before they knew about the ozone hole we used to use refrigerant to freeze the shaft and mapgas on the bearing...but we were not re-using them

[Bryan]

The 3 jaw puller did the job with a minimum of force. Which allowed me to mount the spindle between centres and clock the bearing journals for runout - which was the whole point of the exercise. And runout there is - about .035mm at worst. I tried to set the journals on V blocks and clock the tapers, but my setup was too crappy to get meaningful numbers. Will see what I can do about that, but it's probably academic as I'll need to either try to straighten it or make a new one. I've had modest success straightening slender shafts with a cheap press and patience, but this one is short and chunky. Not much to lose by having a crack I suppose.

The thing felt fine when assembled and greased - smooth & free, no detectable end float. And now I know the spindle is bent, I figure the bearings are innocent till proven guilty. OTOH you may ask, how could a blow sufficient to bend that spindle not damage bearings? My idea for further assessment was to assemble them clean and dry - or maybe lightly oiled - and see how they felt. Ideally with a true spindle.

Thanks for all the suggestions on bearing removal etc.

[pipeclay]

You did turn the headstock centre.

How true are the 2centres to each other

[Bryan]

You did turn the headstock centre.

How true are the 2centres to each other

No I didn't bother as both centres are stationary.

[pipeclay]

How then do you now that the headstock centre held in a chuck is true and not giving your runout.

[Bryan]

How then do you now that the headstock centre held in a chuck is true and not giving your runout.

Because it can't run out if it's not rotating. The lathe is off, I'm turning the shaft by hand.

[Michael G]

Provided the centres do not rotate, they will define a fixed axis. The indicator is there to measure any radial difference. When the shaft rotates on the centres any movement of the indicator will show an eccentricity with regards to the axis and can be taken as the run out of the shaft.

Michael

[pipeclay]

I might be to intoxicated to think clearly, but if you put a centre in the chuck rather than the spindle taper and rotate a job around that centres axis isn't that the same as putting a drive dog on the spindle and rotating the spindle under power.

Also how have you checked the spindle centres to see if they are running true

[Michael G]

I might be to intoxicated to think clearly, but if you put a centre in the chuck rather than the spindle taper and rotate a job around that centres axis isn't that the same as putting a drive dog on the spindle and rotating the spindle under power.


Yes, and if you fed the indicator longitudinally you might think there was a taper when there was not or things were parallel when they were tapered. Here because the indicator is stationary that does not matter. All the indicator can do is show the relative distance between the surfaces passing under the foot.

Michael

[Bryan]

if you put a centre in the chuck rather than the spindle taper and rotate a job around that centres axis isn't that the same as putting a drive dog on the spindle and rotating the spindle under power.

My answer to that is no it's not the same, and a quick thought experiment will demonstrate that.


Also how have you checked the spindle centres to see if they are running true

I just cleaned and inspected them and they looked in good condition so I gave them the benefit of the doubt.

[Steamwhisperer]

Hi pipeclay,
using centres in the lathe is the same as using Bench Centres.
You spin the actual shaft by hand nothing else.

Phil
296845

[Michael G]

Gee Phil - you should know better than to post pictures like that!
First you will have Stuart thinking that he needs one for his indicator collection, then he'll tell us of all the wonderful things he's done on it so a few of the rest of us will decide we have to make one and then...

Michael

[Michael G]

The 3 jaw puller did the job with a minimum of force. Which allowed me to mount the spindle between centres and clock the bearing journals for runout - which was the whole point of the exercise. And runout there is - about .035mm at worst. I tried to set the journals on V blocks and clock the tapers, but my setup was too crappy to get meaningful numbers. Will see what I can do about that, but it's probably academic as I'll need to either try to straighten it or make a new one. I've had modest success straightening slender shafts with a cheap press and patience, but this one is short and chunky. Not much to lose by having a crack I suppose.

Bryan - an overnight thought. Have you checked various places along the shaft? The shaft is chunky and I wondered rather than it being bent whether it has been bad from new. To manufacture a shaft like that the method is probably rough it out on a lathe and then grind the ends so if it was not set up properly it may be that you have vibration just from an eccentric mass. The fix for that could be a skim of the centre section. Bent I'd expect to see a point of maximum TIR but if eccentric there should be the same TIR in several places.

Michael

[PDW]

The 3 jaw puller did the job with a minimum of force. Which allowed me to mount the spindle between centres and clock the bearing journals for runout - which was the whole point of the exercise. And runout there is - about .035mm at worst.

I haven't got the time to think about it too closely, but it seems to me that all you've demonstrated is, that there is runout on the bearing area WRT the centres. That does not *necessarily* demonstrate that there is runout WRT any other area. It's indicative but not definitive. The centres could be out.

I think you need to mount up 3 gauges, 4 would be better, one on each of the machined bearing areas and one on each of the tapered areas. See what runout patterns you observe. Or clock each area separately and record the results on the shaft with a fine tipped pentel pen etc.

PITA doing this sort of stuff - I just spent time tweaking my Chipmaster to turn parallel between centres and got it down to 0.0002" over 5" which was as good as I could manage. I did machine the HS centre in position before I did anything else.

PDW

[RayG]

Hi Brian,

I think here are two things, one is runout, the other is balance.

Even if the taper run out relative to the bearing location is zero, there could be runout elsewhere causing vibration.

If it turns out that it is a bent shaft, what next?

Try and straighten it?
Machine a new one from scratch?
Find someone with a cylindrical grinder?

I'm going to suggest that you ignore it... :) and re-assemble the head, then with the thing running, figure out a way of holding a TPG or similar, or maybe some other existing attachment, and regrind the taper in-situ with the spindle running.

Regards
Ray

[Bryan]

Ray, I like your thinking. Actually that was the first thing that occurred to me, some kind of in-situ truing, but I decided I wanted to know what was going on in there.

Michael, Peter, I did clock it at both tapers and both bearing registers and the error was greatest at one of the registers: .035mm. The amount and location (o'clock) of error was consistent at each place after repeated tests. So I'm convinced the shaft is bent. Attempts to straighten it with my little press were completely futile.

In short, I assembled it and it's now showing .05mm TIR at the wheel arbor. That's about half what I got previously. Why I don't know. Maybe I goofed. Maybe there was an assembly problem. Anyway what matters is, how much runout can be tolerated? Given that the wheels are not a tight fit on the arbors, and that they get trued anyway. I don't have a wheel yet but I powered it bare and vibration was negligible. If it vibrates too much with a wheel I will consider ways of truing the taper as Ray suggested.

To put the project in perspective, all I want to do at this stage is single point tools and maybe drill bits. Super finishes are not required. And start to learn a bit about grinding. If I can achieve those things for minimal cost I'll be happy. And just for the record, I knew this machine was a roughie when I bought it, I'm happy with it, and its condition is no reflection whatsoever on Harty.

BTW, where do you guys buy your wheels (online)?

[Ueee]

What size wheels are they Bryan?

I get norton Surface Grinder wheels (12" x 1" x 3") from my local place, anywhere that stocks norton should be able to get them.

the only online place i know of is AbTec in the UK Abtec4Abrasives / Sanding / Grinding / Polishing (http://www.abtec4abrasives.com/)

Cheers,
Ew

[jhovel]

Bryan (and Ewan),
you may or may not recall that I have a few 12x3x1 and 12x3x3/4 grinder wheels 'surplus'.
Let me know if you can use them.

[Bryan]

Thanks Joe, but I want a cup wheel, 125mm as far as I can tell.
The only online source in Aus I know of is https://www.bolt.com.au/straight-cup-toolroom-white-c-842_995_1007_1008.html
Postage I think was about a $13 minimum a year or two back. Guess that's ok.

[RayG]

Hi Bryan,

I've picked up a few CBN wheels on ebay, a bit mixed, but there are bargains if you are patient, if you want to buy on-line then travers have a pretty good range Flaring Cup Grinding Wheels | Travers.com (http://www.travers.com/118319-53-200-040)

I've bought wheels from Australian Industrial Abrasives (http://www.australianabrasives.com.au/) they don't sell much on-line, the hardest part is figuring out what the best solution is for whatever you are grinding, for general use, white alox is a good starting point.

Regards
Ray

[Stustoys]

Hi Bryan,

Do you have more than one wheel arbor?

Stuart

[Ueee]

Hi Bryan,

Do you have more than one wheel arbor?

Stuart

I have a rouge spare here....now there are plenty of different tapers around but you never know your luck. If not it may fit your grinder Joe-or someone elses. I'll measure it up tomorrow.

Ew

[Stustoys]

If you're going to be changing wheels on the arbor and not arbors on the shaft. I can't see your runout being an issue.... though I've been wrong before. Though I'd say it will be an issue if you end up with multiple arbors with diamond/CBN wheels.(based a sample of one lol)



I did machine the HS centre in position before I did anything else.
Well if arent going to machine it is one setting the that will help, but if you are, it doesnt matter where the HS center is(though it sure will help if you have to remachine it at a later date)

[Bryan]

Ray, yes white alox will be my starting point. I forgot I actually have a thin flaring CBN wheel I got from an ebay seller in eastern Europe a while back. Seems very fine and may be good for finishing and touch ups, but alox will be needed for shaping (should have mentioned I don't use carbide tooling). I recall looking for surface speeds for CBN and not really finding any. Is it supposed to run faster than alox? Also I'm thinking since you can't true it AKAIK, your setup would need to be good. That's why I couldn't get it to work on a bench grinder.

Stu, I only have one arbor at this point, but hope to make some more.

Ewan, Harty said he couldn't ID the taper. It's nominally 1" x 3/4" x 1" long.
Finding one or two would sure save me some hassle.

[RayG]

Ewan, Harty said he couldn't ID the taper. It's nominally 1" x 3/4" x 1" long.
Finding one or two would sure save me some hassle.

Hi Bryan,

Have a look at Sopko, William Sopko & Sons Co., Inc - Products (http://www.wmsopko.com/products.htm) they are a bit exxy, but good stuff.

Regards
Ray

[Ueee]

The one I have is too big. Roughly 1.250x.930x1.750 long. Any takers?

Ew

[Bryan]

I want to make some wheel arbors. Nominal size is 31.75mm (1.25"). The arbor I have measures 31.70, but it's seen better days and I'm not sure which number to aim for. I know there should be clearance on the wheel bore but how much? Does anyone have a newish arbor they could mike for me?

The spindle has some run-out and there's an opportunity to compensate with the arbors. I figure the wheel/arbor clearance tells me the smallest amount of run-out worth chasing.

[Michael G]

My never before used wheel has an ID of 1.254" (31.85mm)
The spindle on the arbor (lightly used, no abuse marks) is 1.230" (31.24mm). The wheels have a soft inner to them, so I would not expect any wear even if the wheel did slip.Provided the wheel clamps up firmly, dressing will take any eccentricity out of the OD. 31.70mm does not sound too awful.

Michael

[Bryan]

Thanks Michael. I will add that I'll be using a straight cup wheel in the first instance and I wouldn't want to be dressing the rim of that too often, for fear it would become unsafe as it thinned. So it seems worth minimising runout. If no-one ventures a larger number I will stick to 31.70.

[Ueee]

Are you running the machine on a vfd Bryan? If not the jerk from the motor starting tends to be enough to move the wheel a tiny bit on the arbor. Since your spindle has runout I would put permanent witness marks on the spindle and arbors so you should be able to put wheels back with negligible runout.

Ew

[Bryan]

Ew at this stage it has a single phase motor. Later I may either do a 3ph/vfd or a treadmill conversion.
Registration makes sense, I will certainly do that. Will be interesting to see how much slip I get with single phase.

Is a mechanical clutch a crazy idea? Or just a belt release?