Thread: How to rivet flat bars?

I think the best approach is to apply the Golden Rule first. The Rule states "If it's not broke, dont fix it". Therefore, I would not think of drilling out any of the rivets. Leave them all alone for now. To remove the cadmium and corrosion, check out this web site. http://www.htpaa.org.au/ Go to the bottom of the screen and click on the left that states "Electolytic corrosion removal". I dont recomend glass beading to remove the cadmium. The cadmium will contaminate the glass beads and can make it very unsafe for further use. Cadmium is extremely toxic when inhaled as a vapour. There have been many reports of people dying after silver soldering a copper boiler for a steam locomotive. The symptoms for cadmium poisioning are EXACTLY the same as those for a heart attack. The victims died from recieving the incorrect treatment, ie, treatment for a heart attack and not poisoning. To ingest cadmium is not as bad as breathing in the fumes as a vapour. However, I would not contaminate the glass beads or spread the dust around from the blasting. Try the electrolysis method first.
Because the metal will be totally clean and the "pores" of the grain of the metal exposed, the parts will rust very quickly. The cadmium being so very thin still alowed the parts to swivel after they were riveted. Any paint applied to the parts will most likely affect the movement of them. This may be something that you will have to accept. The only advice I can offer is to apply a light spray of Cold Gal paint. Use a spray can to paint with, not with a brush from a tin of paint.
The rivets will have been made from a very soft and ductile steel. If you cant buy more rivets perhaps you could make some if you have a lathe. If you decide to replace any or all of them, make sure you can obtain more rivets or very soft steel BEFORE you drill any of them out. Remember the Golden Rule first.
To shape the rivet head, you will need a punch that has the appropriate shape in the end. The punches can be made at home but you will need a lathe to make them. A piece of spring steel bar is ideal to make a set of punches with as these can be heat treated. The "cup" in the punch must be highly polished.

Kody

Looks like a fun project.

The cadmium can definitely be a hazard if you are handling it a lot, but locked inside the case it should be livable. As an alternative you could plate with nickel instead, fairly widely available as a base layer for chrome plating and much cheaper than cad etc. Another alternative would be zinc plating (like the washers in the pics) or zinc passivating (the mottled goldy coloured coating on screws etc)

Re the rivets, you would most likely have to make them or have them made for you as there is not much call for them these days. Most likely when the unit was in production originally, the linkages would be subcontracted to a supplier who stamped them, plated them and assembled them. They probably had an autolathe churning out the various rivets required for the assemblies as that gave them greater sizing freedom for the arms etc.

The rivets were probably set with small tools mounted in an assembly jig. If you could remove the arm(s) as assemblies, you might be able to blast them and plate them as assemblies rather than dismantle and rework them as components.

Guys, many thanks for your help!

Originally Posted by Kody

To remove the cadmium and corrosion, check out this web site. http://www.htpaa.org.au/ Go to the bottom of the screen and click on the left that states "Electolytic corrosion removal".

This is the most encouraging article I've seen since I started researching this project and I think will save me a huge amount of time, effort and cash; I will definitely try this and post the results.

Originally Posted by Kody

Because the metal will be totally clean and the "pores" of the grain of the metal exposed, the parts will rust very quickly... The only advice I can offer is to apply a light spray of Cold Gal paint. Use a spray can to paint with, not with a brush from a tin of paint.

Do you mean that as a result of the electrolytic corrosion removal, the metal will be highly susceptible to further rusting? Unfortunately we don't have Cold Gal over here (South Africa) and I'm having difficulty finding a similar product in aerosol. I expect I will eventually find something suitable though. My concern here is that all the rivets (except one) have escaped the corrosion damage. On the damaged one, the rivet and the two 'joined' bars are damaged. If the electrolytic method solves this, I'm now unsure how to coat the cleaned metal (of the joint and rivet) without drilling-out the rivet.

Originally Posted by malb

As an alternative you could plate with nickel instead, fairly widely available as a base layer for chrome plating and much cheaper than cad etc. Another alternative would be zinc plating (like the washers in the pics) or zinc passivating (the mottled goldy coloured coating on screws etc).

If the electrolytic method doesn't work so well and I have to blast the arms, I think nickel or zinc plating will be the best answer.

Originally Posted by malb

If you could remove the arm(s) as assemblies, you might be able to blast them and plate them as assemblies rather than dismantle and rework them as components.

Now this sounds really interesting! Based on my comment (above) about one rivet and 'junction' being corroded, this may prove to be the ultimate choice. I wasn't aware that it was possible to 'plate them as assemblies'. From this suggesion, I think that even if the electrolytic method works, following this with the 'plating as assemblies' seems to be the best option all around.

Many thanks again.

Plating will only add a thou or so of metal, so it is extremely unlikely that it will lock up the pivots. As a proccess, it generally doesn't like sharp corners or steps, so the plating would taper around the junction point and rivet. This is normally a limitation, but in this instance could work in your favour. A small dob of grease on the rivet and plates at the junctions will ensure free movemnet and help eliminate corrosion.

Note that this only applies to a good working joint, if the joint was already jamming due to corrosion, it is extremely unlikely that the blasting will clear the problem, so it would remain.