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  • Which welding rods?

    Discussion in 'Joining & fabrication' started by Outofmydepth, Nov 8, 2010.

    1. Outofmydepth

      Outofmydepth Active Member

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      I need to weld a bolt onto the pulley connected to a washing machine motor. I am uncertain what the pulley is made of but it is magnetic. I reckon this narrows it down to mild steel or a type of stainless steel. I seem to be aware rightly or wrongly that ordinary welding rods will not weld stainless?. Possibly the reverse is also the case? ie. Stainless welding rods will not weld mild steel. As I have not yet bought the bolt I need to weld to the pulley I could opt for a mild steel bolt or a stainless bolt. Not knowing exactly what the pulley is made of what would be the best option and what rods should I use?

      Thanks

      Outofmydepth
       
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    3. Outofmydepth

      Outofmydepth Active Member

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      As no reply forthcoming I have googled the subject and now generally understand arc welding would not be the first choice for welding mild to stainless.

      However I did find someone who had successfully welded some stainless nut to mild steel with mild steel rods (electrodes).

      I also found someone suggesting using stainless electrodes and in particular type 309.

      Anyone concur with the above advice?

      Thanks

      Outofmydepth
       
    4. AndrewNew

      AndrewNew Well-Known Member

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      Have you considered brazing as an alternative to welding? Brazing generally works well with dissimilar metals, and forms a stong joint. It also does not require the parent parts to be melted.
       
    5. Outofmydepth

      Outofmydepth Active Member

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      Thank you andrewnew,

      I have not considered brazing.

      The reason I have only considered welding is that a pal has lent me his arc welder. In order to braze I imagine I would need a oxyacetylene torch which I do not have. I only have a butane torch for soldering.

      As it was over 40 years ago when I last brazed something (at school) perhaps you could refresh my memory as to the process.

      I imagine the surfaces would need cleaning and suitable flux applying. Heat would then be applied and a brass rod introduced to the work periodically to test if the material is hot enough. Once the correct temperature is reached additional molten brass would be fed into the joint.

      In fact the process would be identical to soldering but using different materials and more heat?

      Outofmydepth
       
    6. AndrewNew

      AndrewNew Well-Known Member

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      That's pretty much it, yes. Silver soldering (hard soldering) is another option (more or less the same process, but using different filler materials, and yes, they are silver-based, so expensive!), but also relatively high-temp. If you can get your parts to bright-red-to-orange heat with your butane torch, brazing should be possible.
       
    7. Outofmydepth

      Outofmydepth Active Member

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      Thanks again AndrewNew,

      Nothing is ever simple.

      As well as needing to attach a bolt to the pulley on the washing machine motor I also need to protect the bearings in the motor which are little more than an inch away. I do not know what the bearings are made of but need to be cautious. I have decided I need to weld or braze with the motor submerged in water up to the bearings in order to keep the bearings cool. I doubt whether I will be able to get the work hot enough to braze with the motor shaft semi submerged in water. However I guess this would not matter for welding given that it is possible to weld under water?

      Incidentally the motor will never be used as a motor again. I only need it for the bearings.

      Outofmydepth
       
    8. AndrewNew

      AndrewNew Well-Known Member

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      It's all a matter of heat input and the rate of heat transfer through the parts. Water is a much more conductive medium than air, so you will need to introduce a correspondingly greater amount of heat if some or all of your part is immersed in water. Acetylene torches and electric arcs generate such a huge amount of heat that you can get your part up to a very high temperature local to the torch/arc (which is the only place you really need it to be hot) very quickly, even if the part is in water. With a butane torch, you'd need a lot longer to get to brazing temperature, and if a significant amount of your part is in water you would probably never manage it, as you said.

      You are right to be careful with the bearings. They might have plastic or rubber seals (which won't like anything much more than 100-200 degrees C, depending on the plastic). Depending on how hot they get, you might also ruin the heat treatment of the bearing rolling elements and the shaft, or get everything covered in oxide scale so they don't run smoothly anymore.

      How about glue?!

      Cheers

      Andrew
       
    9. Outofmydepth

      Outofmydepth Active Member

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      Thanks Again,

      I have thought about glue. Probably Araldite. As an ex golf professional & golf club manufacturer I have glued thousands of golf club heads on with various types of epoxy with 100% success. With this application the shaft is held captive within the hosel of the club head and has a large area of contact. I am not sure whether glueing a flat bolt head to the flat end of a pulley would be quite so successful.

      To quote Harry Hill "there's only one way to find out".

      Outofmydepth
       
    10. AndrewNew

      AndrewNew Well-Known Member

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      He's a wise man, that Harry.

      The araldite works well in the golf club application because most of the load is transmitted from the head to the shaft through the adhesive in shear. Adhesives work very well if you can design your joints so they are so loaded. However, they generally don't like tension or particularly "peel" loads.

      Not sure how your bolt will be loaded, but I suspect that you are right and an adhesive would not be a good choice. I mean't the suggestion in a humorous, "last resort" fashion!

      Is mechanical fastening an option? If you just need a threaded stud, rather than weld a bolt to the pulley, can you drill and tap a hole and then use a piece of threaded rod (or a sawn-off bolt)? You might want a cross-pin or (maybe) some retainer if the threaded rod will have a tendency to unscrew (depends on subsequent direction of rotation).

      Andrew
       
    11. Outofmydepth

      Outofmydepth Active Member

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      Thanks AndrewNew,

      This is part of my project to convert my knackered washing machine to wind power to wash my golf practice balls. In my thread on another board I have made clear mechanical engineering is not my area of expertees (hence my login name). Mechanical fastening would certainly be an option for someone with suitable skills & equipment which unfortunately I have neither. I am intending to progress this project as far as possible by using the modest skills & equipment I possess.

      The whole project would be very easily completed in an engineering workshop but this would leave me £200/£300 worse off defeating the object of the exercise.


      Outofmydepth
       

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