Loctite wheel to shaft

Ive read all there is relating to this subject on here but not satisfied with my understanding. The shaft is a tight fit to the wheel, so tight that it scrapes all the liquid off. If I knurl it it surely will never fit, so what is the best knack to apply? If I make the shaft undersize by even a thou it will 'rattle' around?? Ive got 620 & 675.

Current advice is apparently that an interference fit does work, but [like you] I remain sceptical ...

The traditional way was to make the shaft very slightly undersize, and then "bruise" some ridges [three is a good number], to make it a light press fit in the hole, with space for some Loctite.

The picture, which has been posted on an earlier thread [so you have probably already seen it] is a 2mm diameter pin, and the non-original "nicks" are from the side-cutters that I used to pull it out of the shaft.

MichaelG.

Edited By Michael Gilligan on 26/10/2014 20:39:59

Fizzy,

Have a look at the second graph here. It suggests that the strength is much greater (almost double) for a 0.05mm gap than it is for a 0.15mm gap. 0.05mm is pretty small so, although you think you've scraped all the Loctite off, there is probably sufficient clinging to the microsurface of the 2 metals to effect a strong bond.

Why not do a quick experiment with some scrap to a similar fit to your wheels and shafts? Looks like you need to leave it for a week at room temperature to get maximum strength.

Rod

Rod,

0.05mm [or, about 2 thou] is probably more than the clearance on the body of that little pin that I pictured: The edges of each bruised dent serve to make it an interference fit in the hole and keep it centered.

The instructions for using Loctite with full interference fits do recommend slightly roughening the surfaces, so I'm sure you are correct about the microsurface.

MichaelG.

Turn the shaft to a tight fit. Then undercut the shaft by a thou or so for part of the length that passes through the wheel. So if the wheel is say 1" thick, you might undercut 3/4" of it (centred on the wheel thickness).

The undercut allows room for the Loctite, while the tight fit bits locates the parts.

(If you prefer, you can do several shorter undercut areas).

I made mine a light push fit with a band in the center about 3/8" wide and a couple of thou under size. This method allows the wheel to locate and provides a gap for the locktite. (not my idea by the way) I know it works because when I made the coupling rods I realised the quartering was slightly out. Took quite a bit of heat to release it !!

.

For reference, here's what I wrote in another thread [no pun intended]

Update: ... This very useful document appears to be the current guidance from Henkel, covering Loctite Retainers.

Factor 3 (Page 10), and Factor 4 (Page 11) are particularly relevant to close-fitting joints.

It seems that the advice that we were given remains conceptually valid, but is now presented at the microscopic scale. ... This is good, because it encourages the use of simple "light press fits".

MichaelG.

Hi Fizzy, I've not used 675 and only occasionally 620, but in my old maintenace job we used 638 very often. One particular job was a gear box manufactured by a reputable company. The box used helical gears and the power source was an electrcal motor mounted into the top of the box, I can;t remember the power rating, but they were not micky mouse size, the output shaft size was 4". They had the problem of the pinion gear on the motor being pulled off by the gear it was driving and the driven pulling off its shaft despite this one being retained by a locking nut. every thing was fitted to spec etc. but the problem would not go away and after referring back to the manufacturers, thier solution was to use threadloc on the driven gear lock nut and 638 to retain the motor pinion gear on ithe motor shaft. The motor pinion was a tight push on fit and had a key to resist rotation and had grub screw deep dimpled into the shaft, nothing was changed except the grub screw was changed for a high tensile set screw so that locking wire could be used and threadloc. When the pinion was fitted with a little loctite as recomended it seemed as if the Loctite was just scraped off, but despite removing the set screw and using a hydraulic gearpuller it would not budge without heating to the temperature given in thier technical data. The solution that the manufacturers gave solved the problem completly. Therefore I believe providing you follow Loctite's instructions and that includes proper cleaning of the parts, you should have no trouble with your joint.

Regards Nick.

When I put a new small gearwheel on my backgear shaft I made it a tight fit then lightly threaded it and battered it onto the backgear shaft with a drift

No pinning etc, and it's been fine ever since

You could put loctite into the thread

I had a flywheel get loose on a mid size chain saw. Spun the hole out moderately bad. Saw was junk with no spares longer available. Put couple drops of 242 on the shaft and let it setup. Lasted 20 years until wore out everything else.

ah...675 only works on ferrous/copper (unless you have catalyst) no flaming wonder I was less than impressed!

.

I didn't know that ... but sure enough [see here]

Before investing in special catalysts, it might be worth trying Copper Sulphate solution.

MichaelG.

Am I missing something but when it says Ferrous OR copper alloys then surely steel is ferrous and your cast wheels have iron in them so again ferrous. The primer would be needed for say Aluminium

.

Quite so, Jason ...I don't think you are missing anything; but I don't recall Fizzy mentioning what materials he was using.

MichaelG.

.

Tony,

I have never used 675, or the new catalysts ... which is why I was cautious.

But I have certainly accelerated curing of other anaerobics by using Copper Sulphate.

MichaelG.

The paperwork referenced above says bonds to copper only have 30% of the strength of those to mild or stainless steel. That may have an influence?

Neil

Useful "White Paper" here

[note the active ingredient in many of the Activators]

MichaelG.

how about the cotton reel method?

cheers,

julian

Maybe Fizzy should put a big Glob of weld on teh end of the axle, that will stop the wheel comming off