New Member looking for Machinist running repair information.

UKJay · Oct 9, 2017

Hi Fellas,
I'm new to the community and I would like to ask if there are any methods ( accepted or otherwise) to reclaim enough Outside Diameter on small journals ( 3/4 " and below ) on shafts that run in small ball bearings. I was on shift last weekend and was asked to see if I could facilitate a running repair on a check weigher ( for small packaged frozen food packages ) . When I stripped the unit down the journal that was running in a 608 2RS ball bearing had worn about 20 thou and I had no spares . The repair had to last a 12 hour shift. By the way I am not a machinist I am a mechanically biased maintenance engineer. The only thing I could think of was to put a knurl on the shaft but I could not get more than 40 percent of the journal because of the wall of the knurling tool holder. My repair worked for 4 hours then failed so I would humbly like to ask some of you obviously elite machinists ( judging by reading many threads ) are there any other methods I could have employed?
Thanks in advance fellas,
Jay.

motion guru · Oct 9, 2017

Need more information - is the shaft diameter at the bearing location the same diameter all the way to the end of the shaft where the bearing is installed from? How is the bearing retained on the shaft? (Snap ring? Bearing collar? Nut on shaft?) . . . can you give us a sketch?

yardbird · Oct 9, 2017

Could've globbed some weld on there and then turn the diameter back to size. Hard to say without seeing it.

Brent

UKJay · Oct 9, 2017

Sorry Guys if I was sparse with technical info. The shaft was 410 Stainless , the total length was 300 mm . The journals were 20 mm long and originally machined to be an extremely light press fit in a 608 2RS bearing ( 8mm ID x 22 mm OD x 7mm race thickness. The abutment OD was 12mm i.e. the rest of the shaft diameter was the same.
Jay.

winger · Oct 9, 2017

Emergency fix: Center punch all around the shaft as even as you can, smear some JB weld on, press on the bearing and let it cure.

Measure for a new one before reinstalling.

Dave

Sparky961 · Oct 9, 2017

Welding/turn is a good option, but hard to get enough but not too much weld for a novice. Making a new shaft, if there isn't anything else too complex about it is another one.

Another would be to turn the original down and press a sleeve overtop (with loctite if your fit isn't that precise). Then turn it down to the correct fit once more.

DDoug · Oct 9, 2017

What was the cause of failure to wear a shaft .020 ?

redlee · Oct 9, 2017

Sparky961 said:
Welding/turn is a good option, but hard to get enough but not too much weld for a novice

Welding 410
Better do it properly or it will fail.

UKJay · Oct 9, 2017

To Digger Doug,
The cause of the initial failure Doug is that the Engineering team are unbelievably inexperienced. Lovely bunch of lads but instead of serving a full apprenticeship these lads are starting off as what's referred to as a machine minder, going to college for a year and then being called maintenance engineers. None of them out of nine guys had ever heard of limits and fits. That's how desperate we are in the UK for engineers .As for the technical reason Doug, I'm not sure bud is the honest truth .
Jay.

DDoug · Oct 9, 2017

UKJay said:
To Digger Doug,
The cause of the initial failure Doug is that the Engineering team are unbelievably inexperienced. Lovely bunch of lads but instead of serving a full apprenticeship these lads are starting off as what's referred to as a machine minder, going to college for a year and then being called maintenance engineers. None of them out of nine guys had ever heard of limits and fits. That's how desperate we are in the UK for engineers .As for the technical reason Doug, I'm not sure bud is the honest truth .
Jay.

So the bearing seized up years ago ? and wore down the shaft ?

Where did all the stainless shavings go to in that food environment ?

UKJay · Oct 9, 2017

Thanks to anybody who replies. It's looking like like I will have to immerse myself in all things machining. The department is run on a shoestring budget and don't have a dedicated machinist or anything even close. In fact I guarantee if a machinist turned up on site of the calibre that this forum has I think the guys there would make the sign of the cross and want to burn you at the stake for magical witchcraft !!!
Jay.

UKJay · Oct 9, 2017

To Digger Doug,
Probably in a load of Aldi Cottage Pies or Chicken Masala. As I say Doug, the problems are all stemming from absolute inexperienced bud. The guys are just not serving quality apprenticeships and that is showing up in repetitive failures on a daily basis . Not one of the nine guys can use a DTI clock . It's going to be myself and one more time served guy trying to teach as much as we can in as short as space as possible.
Jay .

Sparky961 · Oct 9, 2017

redlee said:
Sparky961 said:

Welding/turn is a good option, but hard to get enough but not too much weld for a novice

Welding 410
Better do it properly or it will fail.

Click to expand...

Didn't realize 410 had any special requirements, as I've never had to weld it myself. However, the OP was looking for a temporary fix. I'm sure a TIG welder and some mystery rod would have made it last at least for a shift or two.

UKJay · Oct 9, 2017

By the way if anybody can suggest reasons for this chronic shortage I would be really interested to hear. I think the last generation all wanted to do Information Technology and related jobs so there is a shortage of hands on engineers.
Jay.

SeaMoss · Oct 9, 2017

You could try a Speedi-Sleeve. Can't work any worse than what you already did. .020" is kind of a lot for Loctite but they might have a product for that, too. Worth a look-see ...

UKJay · Oct 9, 2017

Actually in reply to Sparky, I would be really interested to find a publication with a host of running repairs. I have googled it but as yet haven't found anything of note. I think it's an under appreciated skill to keep mechanisms working until such time as a permanent fix can be found.
Jay.

Sparky961 · Oct 9, 2017

Another idea that springs to mind, but is somewhat "hacky" is to use shim stock to fill the gap between the shaft and bearing. Maybe add something like Loctite if you want to be paranoid. Chances of getting it running true are low, and it would be trial and error to get a decent fit. There's also the chance of it coming loose and becoming shrapnel or food additive. But it could just as easily solve the problem for a day or two while replacement parts are in transit.

Sparky961 · Oct 9, 2017

UKJay said:
Actually in reply to Sparky, I would be really interested to find a publication with a host of running repairs. I have googled it but as yet haven't found anything of note. I think it's an under appreciated skill to keep mechanisms working until such time as a permanent fix can be found.
Jay.

Agreed. However, they are too often expected to last far beyond their intended use. This gives "duct tape and bubble gum" repairs a bad name.

UKJay · Oct 9, 2017

Thanks Guys, for all your input, it's really appreciated. As I say it would probably be great if I had a host of these temporary fixes up my sleeve. As I've said I'm not a machinist but can get buy with basic stuff and have always worked to close tolerances so I can transfer some of my skills over to maching but wouldn't even be classed as a competent novice amongst you lads. I'm on shift completely on my own on a Saturday night and the job I've mentioned is run of the mill. Actually, they don't really expect much off their team but I expect it of myself if you know what I mean ( professional pride ) So I'm hoping I don't run people up the wrong way by asking basic questions.
Jay.

David_M · Oct 9, 2017

I'm not understanding what size the shaft is that the bearing needs to slip over if you stated that.

You are using a 608 2RS bearing 8mm ID x 22mm OD x 7mm thick. A 627 2RS bearing is: 7mm ID x 22mm OD x 7mm thick. Could you use one after reducing the journal 1mm in a pinch?

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