Needle Roller Thrust Bearings

I've tried the SKF website, but I'm still struggling to understand the best way of installing roller thrust bearings.

I realise you can do without the thrust washers if the machined bearing faces are good enough (but how good do they need to be?)

But I have one face where it will be impossible to machine them without either 'back facing' or just skimming with an end mill. I doubt either approach will give me an ideal bearing surface. So, use the washer - but how should I locate the washer so it is clear of the shaft? Should it be loctited in place, fit in a recess or does it just 'float'?

Neil

Those I've seen on machines etc. I've stripped just float on the shafts. They are not fixed at all. They are sometimes in a machined recess.

John

Edited By John Baguley on 06/11/2014 15:34:43

The thrust bearings on my WM16 just float on the shaft; the washers on thrust bearings are generally hardened to accept the pressure from the rollers ( IIRC around 50-55 Rockwell?   ) if you let the rollers run against a machined face you will eventually have a roller track worn into the machined face.. not good!

George.

Edited By mechman48 on 06/11/2014 16:49:22

Hi Neil,

re thrust bearing...how much work is it going to do...ie like a cross slide wheel (nothing) or as a screw jack screw (very heavy).....?

for heavy work go with the rollers and the lighter side of things of things either use a bronze washer or even some plastic...

but always have something for a thrust washer...... when I've been stuck a well lubed steel washer got me out of trouble, thats until the next strip down....as for the faces.....as long as one say the wheel is super smooth u'll be just fine.......for the diff. to machine or rough side of the thrust face...as long as there are no big lumps and it flat'ish say with a smooth file it'll be ok......the smooth side will spin and the rough will tend to hold the thrust washer.....obviously lube on assembly (but if you go with the rough and smooth, only lube the smooth side) but other than that don't worry to much.....

cheers Frank

Hi niel we use these type. Naxi very reliable in service.

http://www.rwh.hu/data/files/gzWBUdvjBUI0r6UMWTG84Sb73mN6yQh5.pdf

Brian

Thanks folks

These are for the Super Adept rebuild, the back bearing is a bronze bush with a roller bearing and twin adjusting collars either side and a 16-degree (included angle) bronze taper bearing at the front.

Sounds like I should use the washers, at least against the stationary headstock surfaces. Probably worth making a recess, if possible (will be a bit tricky). I may use hardened adjusting collars which will make them redundant for the outer side.

Neil.

Neil, you don't need a recess, if you think about it they self align as long as they are under a little bit of axial pressure.

.

As good as a ground and hardened thrust washer

... not forgetting the all-important parallelism.

MichaelG.

.

Seriously: If you get one surface as good as you possibly can, and then lap the other one to it, you should be in with a chance. The biggest risk would be them ending up as male & female cones.

... A reasonable [space saving] alternative might be to use thin PTFE washers instead of the needle rollers.

The needle rollers at the ends of car gearbox layshafts run directly on the shaft but the shaft is always hardened and ground. Presumably the preferred situation for thrust roller bearings is to run on hardened washers. I imagine the machine or its owner will die of old age before any wear on the washers becomes apparent.

I know a lot of people have reported great success using needle rollers in loco axleboxes, running them on unhardened steel. I suspect Chris is right and whatever I do will outlast me, although I want to do it right if I can.

Considering how little of the machining of headstock is critical - a tenon accurately aligned with two bores - one for the spindle bushes and a second, less critical, bore for the back gear, it's causing me great anguish!

Neil

Neil,

I hesitate to respond being an absolute beginner, but the one thing I have done recently is fit a needle roller thrust bearing into a plain phosphor bronze headstock bearing.; albeit on a Myford M type.

I used the supplied ground washer in the outboard recess of the headstock bearing; this because it's a split design and therefore has a slot which the rollers would otherwise drop into. The existing threaded thrust washer which originally bore onto the bearing had a very nice ground finish and so I used that instead of the second of the supplied washers. This was just to save a smidgeon of space which as things turned out wasn't necessary, so next time I'm in the area I'll fit the second one. My instinct say to use the right thing wherever I can.

The new ground washer just runs free on the spindle and seems perfectly happy to do so. It's a loose finger fit into the recess too, so I don't think nailing it into a rigidly fixed lateral position is important. The lathe itself runs as sweet as a nut with no chatter or end float, so I've taken that as proof of the pudding.

The supplier I used was "Simply Bearings" who seem a clued up outfit with a wide range of Imperial sized parts, modest prices, and a prompt delivery service. I'm just a satisfied customer, nothing else.

Another job I might tackle is fitting thrust bearings into the cross slide and topslide lead screw assemblies, and SB will be my first port of call. I think Arc have some weeny ones too.

... A reasonable [space saving] alternative might be to use thin PTFE washers instead of the needle rollers. I tried that on the cross slide micrometer; it worked well enough for a short while, but PTFE is quite motile and moves under pressure, so the job rapidly sloppied up again. It would be worth a try if you could constrain it at the periphery as well as the end faces. The thrust bearings I used come up at 3.2mm total thickness from memory, so pretty slim.

Eug.

Edited By Eugene Molloy on 07/11/2014 11:44:34

Edited By Eugene Molloy on 07/11/2014 11:58:27

Edited By Eugene Molloy on 07/11/2014 12:05:23

Eug.,

You are correct regarding PTFE.

Very slippery stuff, but it WILL creep unless 'contained' in some fashion.

Headache so no Workshop today.

Geoff - Bummer or what, with all machine ready and waiting

Thanks Eugene, a bit of practical experience always reassures!

I got my bearings from Arc. It was relief to see they fit over the spindle very nicely!

Neil

The biggest problem with roller thrust bearings is keeping crud out as you can't, to my knowledge, buy any form of sealed versions in the smaller sizes. I've used them modifying my lathe feedscrew handle assemblies which is not an overly critical application but where they're in danger of getting a lot of swarf and dust on them, I try to recess them in into a recess only a thou or so bigger than the washers.

For no reason whatsoever, I'll also mention that the large myford vertical milling slide has roller bearings with hardened washers fitted on the feedscrew as standard.

I was considering making the inner of each pair of adjusting rings recessed as a form of 'shroud' over the bearings.

Neil

Without going too far off topic can anyone tell me how roller thrust races work?

Ball thrust races I can understand, but the ones with radially arranged rollers seem a type of oxymoron. If the thrust faces are flat and parallel and the rollers parallel too, then a lot of slip has to take place because of the rolling circumference is different at the ID and OD.

For Neil's headstock best would be to 'backface' as you mentioned, alternatively I think I have seen self aligning ball thrust races (concave/convex backing washers)

Ian P

Just for clarity, please note that I did suggest a thin PTFE thrust washer, which is inherently stiffer in compression [than a thick one]. ... I was thinking in terms of about ten thou' thick, or maybe less.

'twas just a thought ... the roller thrust bearing is almost certainly a better solution.

MichaelG.

Edited By Michael Gilligan on 07/11/2014 22:10:16

Neil, perhaps the shim washers that are found on things like electric motor shafts, they are maybe .005" thick, and hard. My supply comes from 50+ years of collecting.

Ian S C