Anaerobic Adhesives

[Antman]

Hi guys,
I’ve had a bit of experience with thread lock type anaerobic adhesives now I want to try a bearing retainer type, made locally in Sarf Efrica by Pratley. Pratley products are pretty good, over here we believe that Pratley epoxy is the only SA product to have gone to the Moon. How strong is a bearing retainer type glue? For instance, if one has a close fitting slip fit shaft glued in a pulley can one transmit usable torque, say the glued area is around 2 square inches? How do you eventually disassemble the glued joint, assuming that it holds?
Thanks,
Ant

 

[Blogwitch]

Ant,

If you follow the destructions on the bottle to the letter, you are almost guaranteed a good joint with these adhesives.

If they can stick full sized loco wheels on with the stuff, I am sure it can take what you have to throw at it.

Be careful you get the right grade for the job in hand, I keep in stock three different grades, and that covers everything I really need.

To get the joints apart, warm up gently from both sides of the joint with a small blowtorch, let the heat penetrate a little, and the joint should fail enough for you to get it apart.


John

 

[kvom]

I used Loctite 620 to adhere my loco drivers to their axles (.875" diameter). The larger the diameter of the shaft the stronger the bond. With this size shaft, I found that I still needed my shop press to remove the wheels after application of the torch.

 

[Antman]

Locomotives wheels? A reallly good press fit first? Thanks John and kvom, I'll try it with confidence in my application and see if it works for me.
Ant

 

[Blogwitch]

Ant,

Not a press fit, there has to be a tiny gap for the adhesive to sit in to do it's job.

If I was going to fit something like that in a model engineering capacity, I would make the shaft a couple of thou too small, then the area it sits inside the wheel or hub, do a straight knurl on the shaft. That should give you both a press fit AND somewhere for the adhesive to sit inside.

The knurled press fit will keep everything square while the adhesive sets.

John

 

[kvom]

My wheels are a smooth sliding fit on the axles, probably about .002" clearance. 620 will work up to .015" according to the docs.

Since I had to quarter them accurately it was necessary to be able to rotate them smoothly once installed with the adhesive in place. In fact, the loctite started to set within 10 seconds meaning I needed some coordination once it was applied. With smaller diameters you have more time to work before it stiffens, probably 30-45 seconds at 1/4" shaft.

Directions recommend applying to the shaft and then rotating it inside the hole to spread the fluid evenly.

 

[mu38&Bg#]

The spec sheet for the adhesive will have figures for cured shear strength. You can figure torque or axial load based on this and the surface area. Disassemble by heating to the temperature noted in the documentation.

Greg