When is it necessary to Loctite a shaft in a bearing
When is it necessary to Loctite a shaft in a bearing
(OP)
I need some guidance in determining whether or not I need to lock a shaft in a bearing. We have a bearing block that has two deep groove ball bearings installed (one on either side). This block houses a 12mm shaft. The shaft is positioned in place by securing a collar on both sides of the shaft. The shaft rotates at 1000 rpm...





RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
You need to determine the load condition, i.e. which ring sees the load rotating. That will be the ring that requires a tighter fit. e.g. standard electric motor running a V-belt system - the inner ring see the load rotaing. Outer ring sees a stationary load. Hence the tight fit on the shaft.
If you are geting creep, then you don't have enough interference.
Internal clearance will be modified, depending on the degree of interference, butyou can overcome that easily by using a C3 or even C4 bearing.
Lester Milton
Telford, Shropshire, UK
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
And if they are critical to your plant stock them in your stores.
Lester Milton
Telford, Shropshire, UK
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
CM now becoming a 'standard' for electric motors, especially ones that have to run quietly. This is a clearance range somewhere between normal and C3; i.e. slightly tighter on average than C3.
Lester Milton
Telford, Shropshire, UK
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
1. If you have a tight fit (which ideally you should) and press the bearing on to the shaft there will be no clearance for the Loctite
2. There is always a danger that you might get Loctite in the bearing
3. Bearing removal may require heating or excessive force
4. Before Loctite was invented, bearings were successfully installed without it
5. No bearing manufacturer recommends it, as far as I know.
(This does not necessarily mean anything - but could give them an excuse if anything goes wrong)
RE: When is it necessary to Loctite a shaft in a bearing
My work area is absoloutely not a perfect world
RE: When is it necessary to Loctite a shaft in a bearing
ago and was wondering if anyone recommended it
to keep the bore or od from creeping around
the circumference. I do not know if creep is
a bad thing on is expected in all applications.
Maybe with a press fit, this does not happen.
RE: When is it necessary to Loctite a shaft in a bearing
rnd2 : You are obviously a Brit, since you said "fitters". In the UK, (except in mass production), it still seems to be tacitly assumed that things will have to be adjusted at assembly, just as they were in the days before interchangeability was developed in the US. But in the US, there are only "assemblers" - a rather different mind set. Now if you look at the last sentence of my very first post, right after the initial question, you will see that I basically don't totally disagree with this "fitter" that you mention, if you interpret his being confronted with an undersized shaft as "an emergency". This fitter of yours brings to mind my very first undergraduate summer job in a machine tool company in the UK (it was a subsidiary of a US company and has long been defunct). Being one of the "lowest of the low", I was put to work helping a fitter, whose job was to assemble gearboxes for a line of large machine tools. This guy had been a plumber in his previous job, and I later came to recognize that some of his practices were outrageous, although I didn't know any better then. He hand polished the bearing location diameter of nearly every precision ground shaft that went into a gearbox, until the bearings would just slide on (he didn't "approve" of tight fits either). It wasn't long before he had me doing this for him, and of course I went a bit too far in some cases, being relatively unskilled. These shafts were quite complicated and expensive, so when this happened, to save my butt, he would furtively look around the shop to see if anyone was looking, and then put three pricks with a center punch on the shaft surface so that the bearing would appear to be tight. I have often wondered what happened to those gearboxes! We did have Loctite in those days, but it was relatively new then and wasn't quite "acceptable". If he had used it at that time, and it had been discovered, we would both have been in big trouble. But it would certainly have been better than the prick punches, except for the problem of disassembly.
RE: When is it necessary to Loctite a shaft in a bearing
Close, but no cigar. We have fitters in Australia too.
I now understand the remedy for removing a loctited whatever is to capitalise on two things:
1) Over 75 deg.C bond strength reduces significantly and is virually non-existant above 100 deg.C.
2) Loctite apparently has low impact resistance.
Applying this logic suggests increments of increased heating and belting err bashing err tapping til it comes off.
RE: When is it necessary to Loctite a shaft in a bearing
RE: When is it necessary to Loctite a shaft in a bearing
The rolling components are supposed to roll, and the stationery components are not supposed to move. Anything that keeps it that way and does not impede the rolling components has got to be beneficial.
As far as Loctite goes there seems to be two mind sets:
Don't use it: It's not required if the job is perfectly engineered (OEM) and later the stuffed bearing will be easier to replace. When it is time to replace the bearing heat is'nt necessary so it is entirely possible to save other bearings that may be in the train.
Use it: It is required if the job is'nt quite perfectly engineered (maintenence) and the stuffed bearing and all the others in the train are going to be replaced anyway because its not worth risking leaving old bearings in the train.
Hope this helps
RE: When is it necessary to Loctite a shaft in a bearing
Reasons for not using loctite:
-could contaminate bearing
-could cause bearing not to seat properly against shoulder
-could actually build up more under some areas of the bore causing deformation of the bearing ring and pinch points(most important)
Reasons to use:
-only if shaft fit and finish is poor or if the bearing is being replaced and the worn shaft is not being re-done.
There are definitely occasions when using a retaining compound is going to help. The most important suggestion I have is that the proper compound be used. Loctite and others make a compound for this express purpose. Using threadlocker is a bad idea and is more likely to cause problems.
Hope it helps