Loc-tite and a light press fit?

CalG · May 12, 2015

Bronze bush into Alu housing

2 " diameter OD 1.75 ID .0015 interference fit.

Does "Bearing Mount" Loc-tite, offer anything to the fixing?

Seems like it would just wipe away.

I applied it anyway ;-)

comments?

tdmidget · May 12, 2015

If it is a press or otherwise interference fit, where is there any room for Loc-tite or anything else?

true temper · May 12, 2015

I would say it adds strength to your assembly.

Years ago I was pressing some bushings in a scraper hitch, stoped to re rig, and it locked up had to cut new bushing out with torch. Next new bushing got some lite oil never had a problem after that.

CalG · May 12, 2015

tdmidget said:
If it is a press or otherwise interference fit, where is there any room for Loc-tite or anything else?

Your response is my question! ;-)

RC99 · May 12, 2015

tdmidget said:
If it is a press or otherwise interference fit, where is there any room for Loc-tite or anything else?

No surface is completely smooth without imperfections that are essentially voids in press fits...

CalG · May 12, 2015

Molecules are "very small" ;-)

tdmidget · May 12, 2015

RC99 said:
No surface is completely smooth without imperfections that are essentially voids in press fits...

And the tiny amount of loc-tite or any other super goo in those spaces would have no effect at all.. A real interference fit eliminates the voids that you imagine to be there.

CalG · May 12, 2015

td

So is it a matter of "real" press fit? Where does reality begin?

homanfab · May 12, 2015

Actually Loctite 648 bearing retaining compound works even with a shrink fits. Recently ran a test at work where we applied 648 to the outer race of needle roller bearing to test the retaining strength. A bearing without the Loctite pressed out around 5000 lbs. The one installed with the loctite required 5 to 6 times(I don't recall the exact number of the top of my head) the force to break the bond and then pressed out similarly to the other bearing. This was done in a load frame so I have the force plots. You could see where the Loctite had bonded to the very smooth bearing race even though it was a press fit.

tdmidget · May 12, 2015

But, again, where was the space for the Loc-tite? a shrink fit has NO room for any such compound. A press fit should have very little if any.

CalG · May 12, 2015

subjective not qualitative...

molecules are VERY small.

true temper · May 12, 2015

A shrink fit is different than a press fit.

Edit, that bit of advice along with a lot more is from Gbent.

dgfoster · May 12, 2015

homanfab said:
Actually Loctite 648 bearing retaining compound works even with a shrink fits. Recently ran a test at work where we applied 648 to the outer race of needle roller bearing to test the retaining strength. A bearing without the Loctite pressed out around 5000 lbs. The one installed with the loctite required 5 to 6 times(I don't recall the exact number of the top of my head) the force to break the bond and then pressed out similarly to the other bearing. This was done in a load frame so I have the force plots. You could see where the Loctite had bonded to the very smooth bearing race even though it was a press fit.

Isn't interesting when someone has actually tested a question as opposed to "reasoned out" the answer.

If you look a a part that has been pressed in and then pressed out like the outside of a bearing you do see where the grinding texture has been disturbed as evidenced by more or less narrow lines that run parallel to the directionof pressing that have been worn into the ground surface pattern. But more than half of the total surface still shows the original ground surface pattern. Loctite applied to such a bearing prior to insertion must be retained in the intact portion of the surface and thus is ready to do its job. (Hmmm, this sounds like a "reasoned out" answer.

) I wonder if homanfab was able to see traces of loctite in the grooves of the unscored ground pattern areas.

Denis

CalG · May 12, 2015

It was a Press fit, though I did chill the bushing, and tried to keep the housing warm. it was an "in door, out door"operation in winter ;-)

dgfoster · May 13, 2015

Cal, So on good cold Vermont day there might be 100 deg F difference or so in vs out. The bronze with a thermal coefficient of about 10 millionths per inch per degree could have shrunk somewhere near 2 thou over the 2 inch diameter---certainly significant. Unless I dropped or added a zero....

Denis

HuFlungDung · May 13, 2015

In the process of sleeving bearing seats in electric motor endbells, I usually install the sleeve with about .005" interference ( sleeve is only .050" wall) and a thin grade of anerobic cement ( I think it's a Devcon product that I've been working from the same bottle for 20 years

). I use it as a lubricant, but am also cautious to press the sleeve in very quickly, as I have had the joint seize when part way in, if any sort of lengthy delay is made in installation. I always figured there is plenty of space in the toolmarks of a smooth turned surface to hold a bit of a residue.

CalG · May 13, 2015

dgfoster said:
Cal, So on good cold Vermont day there might be 100 deg F difference or so in vs out. The bronze with a thermal coefficient of about 10 millionths per inch per degree could have shrunk somewhere near 2 thou over the 2 inch diameter---certainly significant. Unless I dropped or added a zero....

Denis

The kind of numbers I was considering, but a 50 degree spread would be more realistic.

But that has little "bearing" on the wiping clear of any voids.

atty · May 13, 2015

Well....gee, I haven't seen any posts that indicate that the application of Loctite "reduces" the bond, so what's the downside? Are the "Press Fit Police" going to knock at your door for using it?

Anybody???

adama · May 13, 2015

IMHO on turned parts it really helps, as others have pointed out it fills the surface imperfections, anything that reduces gaps between the parts - increases the areas loads are spread out too will increase product life. loctite use to claim a reduced chance of gualing with there products from memory too.

Also worth adding, i have also personaly seen it's use result in less corrosion on all kinds of fit, it sealed of the imperfections water would wick into!

Mike1974 · May 13, 2015

There are actually a few different kinds of Loctite for 'gluing' bearings or sleeves or whatever it is you want to do. I know one of them is for interference fits like you describe, and one is actually for slip fits. It actually fills the gap (IIRC the bottle says up to .005", but I don't know about that) and really does glue the two pieces together. I think there is a third one as well. I think they are labeled something like use for "press fit xxx tolerance", "light press fit xxx tolerance", and "slip fit xxx tolerance". I might be wrong on the 3 different kinds, but I know for sure they have one for 'slip fits' and one for 'press fits'. I was told that one of the big die set manufacturer bored their bushing holes oversized by a few thou or so and then used the Loctite slip fit type stuff to glue the bushings in place. Not sure about this. Why glue the bushings in but press (and I mean PRESS) the guide pins in? Maybe to prevent the bushing from collapsing as it is pressed in...?

edit: search MSC website and filter the Loctite stuff for 'retaining compound' you will find quite a few different kinds

Loc-tite and a light press fit?

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