Highly polished shafts and holes might not be good candidates for adhesive joint.

Recently I have tried something like that:

Tolearances for interrupted fit were machined. Part with a hole was warmed to modest 100*C. Shaft was immersed in liquid nitrogen for 10 minutes (hospitals and higher end pubs have it, pubs are using it for making icecream – just smile to manager and come with suitable 2- 4 pint household Thermos flask – do not tighten it too much – there must be a way to escape for boiled off gas). You can store it for few days before is gone. Liquid nitrogen is cold (-196*C) – take care. Spilling it over hand usually does next to nothing as it boils off before contact with skin but touching metal cooled to -196*C guarantees nasty frostbite in no time at all. Now , with aid of thermally insulating gloves, insert/press shaft into hole and let it expand upon warming. Do your job reasonably fast, before shaft warms itself. You may pour liquid nitrogen to wide mouth thermos or thermally insulated thin walled pot for the job.

You won't disassemle it easily…

Martin

Have you tried cleaning with acetone,ive heard people saying it acts as a cheap activator for aluminium .Loctite recommend using their surface activator `7649 primer N ` for aluminium when using 603 ,which is an aliphatic amine and acetone .

What are you cleaning the metal with ? I use acetone .

Make up a test piece using steel and see if it goes off then , maybe there is a problem with it using alloy or what you are using to clean the parts is affecting the bonding agent ?

If the steel test piece gives the same results and you are using acetone to clean everything maybe your bottle of retaining compound is crook and if you are leaving it overnight and it is still not going off then i would be looking at a new bottle .

The test piece need only to be a drilled and reamed hole in a piece of scrap that accepts a suitably turned pin from another piece of scrap and would only take a few moments to make .

Edited By XD 351 on 13/10/2017 12:08:52

I don't know if you're looking for anything other than Loctite but I've used this other british make called bondloc, this is the specific one; **LINK**

It seems to hold together very well and the strength is a lot better than other locking adhesives I've used.

Michael W

Hi Robin,

If I could just reply to your original post.

Loctite 638 is in my limited experience a really strong bond

I have just made a crankshaft, 1/4" diameter, using loctite 638 to to bond it to the crank webs which are made from 5/16" mild steel plate. Same for the crank pin also 1/4" diameter.

Rock solid, I have pinned them as well with 16g panel pins but it was hardly necessary.

Hope this helps Geoff

Hi Jason/Robin

I thought I would share this with you. The first photo is a scrap piece of aluminium with 4 x 1/4" holes drilled through it. The end hole has a 1/4" round bar loctited in with 638.

I left this overnight and to test the strength I clamped the bar very tightly in the bench vice using soft jaws. I then tried to break the seal by rotating the alloy bar. The whole assembly rotated without breaking the joint. I tightened the vice more as hard as I could and the joint still remained firm. I was amazed how strong it was.

The second photo is the crankshaft for the Jepson engine, again 638 on the shaft and crank pine, and incredibly strong joints.

best geoff

Comparing Loctite 638 and 603 is made unnecessarily difficult by the slightly different formats and contents of the TDS data sheets. How hard would it be for Loctite to use a common format and provide sensible explanations of how to decide which to use when. Methinks ulterior motives for the "superficially same but actually different" style used.

Anyway 638 TDS gives Compressive Shear Strength between same material pins and collars of 4,200 psi for steel and 2,700 psi for aluminium. Pretty much in line with the graph although that actually implies about 2,500 psi by my maths.

603 TDS doesn't give all that information but it does give 3,260 psi for steel pins and collars. Graphs on the one I downloaded imply that bond for aluminium gets up to around 75% of that for steel viz :- 2445 psi.

So its pretty much a wash after a week.

Have to assume that Compressive Shear Strength is actually a meaningful parameter for behaviour out in the real world. I think I can see how its a reliable and reasonably easily measurable test parameter but what it adds up to in the real world I know not. Can do the maths but it still doesn't mean much. Torque on a specified size bar in a specified hole would be so much easier for ordinary folk. We've all sheared bolts in the past so have some sort of feel.

One really annoying thing about Loctite (and other suppliers of similar nostrums) is that its not made clear how quickly headline performance drops off if you don't do things exactly right. Reading between the lines of several less than satisfactory conversations with Loctite tech reps I'd hazard a guess that most casual users are working around the 1,500 psi region even with the uber strong stuff. Still quite a lot as a 1" shaft in a 1" deep hole is "pi" square inches. Implies something over 4,500 lb to push it out even at 1,500 psi if you have full coverage. But it isn't that simple on a real component.

Clive.

Edited By Clive Foster on 13/10/2017 18:04:27

Edited By Clive Foster on 13/10/2017 18:22:55

Not specifically relevant to this thread but loosely related by liquid nitrogen. Back in the early 70's I was working as a contractor in an engineering hangar at Luton airport, we were engaged in servicing a Boeing 707 which belonged to some obscure African airline. I was working on one wing and alongside me was an apprentice who had been given the job of replacing a bush holding one of the flap tracks, and he was struggling there was no way he could get the bush to even enter the hole where it was meant to be. I watched him struggle and get more and more frustrated, eventually I took pity and took him to one side and said to him was there anywhere, either in the hangar or nearby, where he could get a small quantity of liquid nitrogen, he looked at me as though I was from another planet then it dawned on him what I was proposing he should do to achieve his task. He went off in seartch of the required liquid nitrogen and very shortly returned clutching a metal receptacle, with heavily gloved hands, which contained an amount of the required liquid, merrily bubbling away. He proceeded to immerse the bush in the liquid for a few minutes then took it out and with his gloved hands offered it up to the hole in the flap track, it literally fell into place and when it warmed up it was well and truly secured. A little while later his mentor came by to see how he was getting on with his task and was gobsmacked to see the task completed. He quizzed the apprentice as to how he had succeeded so easily and the apprentice told him about using the liquid nitrogen, his mentor said to him how had he known about how to use it and he replied that a friendly contractor had explained what to do. Engineering is always a learning process, we never stop learning.

Dave

I would knurl them slightly so there is somewhere for the Loctite to sit. If there is no gap then there will be very little adhesive in the joint.