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"Bonding" stainless steel

What to use?

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Gary Murphy 113/08/2020 10:33:18
462 forum posts
22 photos

Before I start to locate the materials would like to know if its possible to bond Stainless steel.

This is not for Aircraft use. I need to make some tie rods which are not easy to bend. So thinking of Stainless steel tube, apx 6mm in dia. Then run a stainless threaded rod through the tube. Depending on the sizes available this might not be a snug fit SO would I be able to "bond" the rod? I am expecting it to be a fairly good fit so getting "epoxy" etc down the gap will be hard IF it will even stick SS.

Was wondering if the liquid that sticks seals or bearings would do the job OR would the theaded area cause too big a gap?

I just feel the bonding of the 2 will give more strength against bending.

any info would be great,Also if anyone knows a stockist of smaller size SS that would be great. I have only been able to find much larger stock. Apart from ordering from China!

Denis Watkins13/08/2020 10:49:41
4633 forum posts
129 photos

EBay has supplied me small sizes, tube and rod, threaded and plain so check there Gary.

The is even a chap manufactures spacers to your drawing but can add up in price.

As for bonding, more info is required like length and load

But bonding is viable with the usual case of roughing up polished surfaces

Edited By Denis Watkins on 13/08/2020 10:55:56

Martin Harris13/08/2020 10:55:11
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9501 forum posts
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Posted by Gary Murphy 1 on 13/08/2020 10:33:18:

Was wondering if the liquid that sticks seals or bearings would do the job OR would the theaded area cause too big a gap?

I can't help with the general question - some more detail might help but these products are anaerobic...or in other words, set when air is excluded so rely on close fitting joints and would be no use in the situation you've described.

If you're using studding, lock nuts at each end might add some stiffness to the assembly.

Edited By Martin Harris on 13/08/2020 10:57:11

Chris Walby13/08/2020 10:55:16
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1323 forum posts
332 photos

If its a fairly tight fit (like fitting a bearing) then Loctite will do a treat. If its a wider clearance the again Loctite will most likely do a product that works., just make sure the surfaces are clean and grease free

Loctite used to have a very good customer support line where advice was very helpful...if they didn't have a product then nail was the last resort!

To contact Loctite Industrial, please click here. For Loctite® Industrial Products call 800-562-8483 or visit Technical Service for Loctite Industrial Products

PS - One last question...choose wisely if you ever want to get things apart, the bond may be stronger then the steel its bonding to !

Robin Colbourne13/08/2020 12:27:06
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640 forum posts
17 photos

At one time I was a manufacturing engineer for a composite cover intended for the Rolls-Royce Trent Engine. This cover had a stainless steel plate on the front for electrical connectors and the intension was that the edges of the plate would be moulded in to the composite cover. Having spoken to The Welding Institute (TWI), who despite their name, are concerned with all sorts of bonds in all materials, stainless steel was a poor choice to get this bond. According to TWI, the barely perceptable oxides that form on the surface of stainless steel almost immediately make a reliable bond very hard to achieve. All you can do is abrade it really well to get the maximum possible surface area, and make sure you have 100% adhesive coverage.

Having said all that, I achieved a decent repair with a piece of stainless steel tube and epoxy when fixing one of the roof supports on our gliding club golf buggy (used for pulling the gliders back to the launch point). The support had fractured through a transverse bolt hole. The stainless tube I had was a about a 1/16" larger in bore than the roof support. I abraded both bits really thoroughly on the mating faces and cleaned them with IPA (propanol).

Both the inside of the outer tube and inside of the inside one were completely covered with 24 hour epoxy. Once the parts were assembled, I heated them with a hot air gun to about 70°C get the epoxy as runny as possible, so it wetted in really thoroughly to the abraded surfaces.

After curing, the bond seems fine. I must have done this a couple of years ago and its still holding despite the buggy getting driven many miles across a pretty rutted airfield ever since.

The epoxy is just ordinary domestic 24hr Araldite although it must be close on 50 years old by now. So much for shelf lifes!

Robin Colbourne13/08/2020 12:37:23
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640 forum posts
17 photos

Another thought Gary. If you have to bond the parts after they have been assembled, could you mount the tube vertically and form a funnel around the top where the tie rod goes in. Then fill the funnel with warm 24hr epoxy and warm the tube so the now low-viscosity epoxy runs down between the two parts.

Youi could even consider squeezing the tube in a vice to deform it onto the tie rod to create a mechanical connection.

Edited By Robin Colbourne on 13/08/2020 12:49:16

Gary Murphy 113/08/2020 13:01:12
462 forum posts
22 photos

Thanks for all the help and tips guys. I think the Epoxy is worth a try then. The threaded rod that will run through the tube will have a ball link at each end so will be kept in place. do you think epoxying the rod would add more resistance to bending? Just wondered how much the tiny amount might weaken..

6mm tube with 1.5mm wall thickness will allow a 3M threaded rod to be used. I need the 3M because the links take 3M.

Doc Marten13/08/2020 13:22:26
729 forum posts
7 photos

Is Silver brazing not an option?

jrman13/08/2020 13:30:11
417 forum posts
3 photos

JB Weld will flow if warmed and sets "solid".

Robin Colbourne13/08/2020 13:32:08
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640 forum posts
17 photos
Posted by Gary Murphy 1 on 13/08/2020 13:01:12:

Thanks for all the help and tips guys. I think the Epoxy is worth a try then. The threaded rod that will run through the tube will have a ball link at each end so will be kept in place. do you think epoxying the rod would add more resistance to bending? Just wondered how much the tiny amount might weaken..

6mm tube with 1.5mm wall thickness will allow a 3M threaded rod to be used. I need the 3M because the links take 3M.

Gary, if the rod is continuous from one ball link to the other, then the rod will be taking the tensile (pulling) and compressive (pushing) loads. The tube is simply there to prevent the rod from deflecting under compressive loads. The actual forces being directed into the tube will be quite minimal in comparison. The epoxy is there simply to transfer these loads into the tube and prevent the tube from sliding up and down the rod.

Provided you use an epoxy which sets really hard, i.e. 24hr instead of 5 minute, you should be fine. As I mentioned previously, warming the epoxy to reduce its viscosity is the best way to make sure you get the tube filled with epoxy and not trapped air.

Gary Murphy 113/08/2020 19:26:43
462 forum posts
22 photos
Posted by Doc Marten on 13/08/2020 13:22:26:

Is Silver brazing not an option?

Doc, I am asking what will "stick" SS, Does it sound like I could Silver Braze!!!!!!!! smiley

Doc Marten13/08/2020 21:14:20
729 forum posts
7 photos
Posted by Gary Murphy 1 on 13/08/2020 19:26:43:
Posted by Doc Marten on 13/08/2020 13:22:26:

Is Silver brazing not an option?

Doc, I am asking what will "stick" SS, Does it sound like I could Silver Braze!!!!!!!! smiley

 

LOL!

Fair enough smiley

What about Silver solder?

Edited By Doc Marten on 13/08/2020 21:18:31

Ben B13/08/2020 22:19:30
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1453 forum posts
4 photos

Which grade stainless. Some are far from strong. "Hard to bend"- define. Is brittleness an issue? On a tie-rod I'd go with rigid but springy. I recently used some 16mm solid 316 stainless rod for a hammock post spiggot. It bent like well cooked pasta! Stainless Steel is a family of metals.

Ben B13/08/2020 22:27:01
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1453 forum posts
4 photos

I may be wrong but I think 400 grade stainless can be annealed and heat treated due to higher chromium content and a different crystal structure. For a tie- rod unless in a marine environment I would opt for heat treated carbon steel and for me that would be a "blue glue"(ie mig welding) job.

Andy Stephenson14/08/2020 11:29:30
221 forum posts
36 photos

When I worked in mechanical engineering back in the 80s we used an adhesive called Belzona Molecular which was an Epoxy with steel powder mixed in. It was like a very superior JB Weld. I checked to see if it was still available and found this...

https://www.belzona.co.uk/en/products/purpose/metal-repair.aspx

It appears they have updated their product range since that time but it looks like they have something worth a go.

A.

Gary Murphy 114/08/2020 12:48:28
462 forum posts
22 photos
Posted by Doc Marten on 13/08/2020 21:14:20:
Posted by Gary Murphy 1 on 13/08/2020 19:26:43:
Posted by Doc Marten on 13/08/2020 13:22:26:

Is Silver brazing not an option?

Doc, I am asking what will "stick" SS, Does it sound like I could Silver Braze!!!!!!!! smiley

LOL!

Fair enough smiley

What about Silver solder?

Edited By Doc Marten on 13/08/2020 21:18:31

Go on, Rub it in !!!!

Gary Murphy 114/08/2020 12:59:22
462 forum posts
22 photos

Regards the SS qualities what I have found so far is A4? not marine grade.

The tie rods are for suspension trailing arms. I thought SS was tougher than "normal" steel. Always find it harder to cut. Also was going to go with SS for corrosion benefit. The latter is not vastly important.

I need something that will not bend easily.So is they a better material choice for this application, needs to be 6mm OD tube. Which needs a M3 threaded rod to pass through. Also needs to be easily available in shortish lengths . I need about 24 inchs,over 1meter makes shipping harder.

thanks for all the help so far

Doc Marten14/08/2020 13:53:17
729 forum posts
7 photos
Posted by Gary Murphy 1 on 14/08/2020 12:48:28:

LOL!

Fair enough smiley

What about Silver solder?

Edited By Doc Marten on 13/08/2020 21:18:31

Go on, Rub it in !!!!

Honestly Gary, I'm just trying to help.teeth 2

secret

 

Edited By Doc Marten on 14/08/2020 13:54:37

Bruce Collinson14/08/2020 14:45:08
558 forum posts

Would getting a clever engineer to turn down some suitable bar to M3 than heat treat it be overkill? If as I suspect your assembly needs to operate in compression as well as tension, this might be a better solution. Also, will the strength of such an assembly exceed, considerably, that of the M3 fittings to which it will attach?

Intriguing! Let us know your solution in due course.

BTC

Gary Murphy 114/08/2020 17:30:48
462 forum posts
22 photos
Posted by Bruce Collinson on 14/08/2020 14:45:08:

Would getting a clever engineer to turn down some suitable bar to M3 than heat treat it be overkill?

BTC

I was into carp fishing years ago and used to get adapters and fittings made up from machine shops BUT all the places I used to use have long gone. They would take on small jobs or do it in tea break etc.

I would imagine a shop now would all be high tech with a reception ready for a large order or look at drawings,no guy in dirty overalls now.

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