Zinc or Aluminum - Identifying Bracket Material

While seeking a replacement bracket for a Rockwell Carbide Tool Grinder,
suggestions have been made about repairing the part mechanically, by
brazing and by GTAW.

The part is not magnetic and feels too light for it to be made of cast iron.
On this basis, brazing no longer seems to be an option.

How can I determine whether it is cast from aluminum or zinc? Is the
precision of the casting (illustrated below) too good for it to be made
of aluminum?









.

Looks like the same part and material as the trunnions on a Rockwell bandsaw. In that case, it is the old proverbial pot metal. It's not going to be weldable. You can either try to put a mechanical fix on it or make a new one out of aluminum (best fix).

Thank you

Ken R.

Fixed.


On the subject of determining bracket material, some suggestions offered
elsewhere are as follows:

awemawson said:

A drop of hydrochloric acid will fizz and give off hydrogen on zinc
but not on aluminium. Potasium hydroxide will fizz on aluminium and strip
the surface but not on zinc

Click to expand...

vincemulhollon said:

... acidic pipe cleaner for a short time will corrode zinc.

One droplet of lye alkaline pipe cleaner for a short time will corrode aluminum.

If both corrode, you have pot metal made of both.

Click to expand...

The gentleman who performed the repair mentioned that he felt this
bracket contained a significant portion of zinc, due to the blow-out that
occured when he initially tried working it. (Porosity is visible at the outboard
end of the slotted section in the third image.)

.

I actually has some luck arc welding some pot metal a while back. Unfortunately I have no idea what I used, I just scored a collection of different sticks and kept trying different ones till it worked. It was a handle that doesn't take much stress, I didn't dare drop test it. I also aren't even good enough to be considered hack grade at welding.

I used to weld a lot of carburetors. They were aluminum/high zinc content.

These were real porous. When you would start the weld it would splatter/fizz and leave a white soot on everything ( similar to galvanized). It also had a galvanized smell. You would have to weld & grind a few times. The first couple of welds looked like they had cigarette ashes in them. After you got a "bed" of aluminum down, then the following weld beads would apply good.

They used to have me to do welding demonstrations for the TIG classes at the college I attended.

I still do a quite a bit of transmissions, bell housings, alternators, & other automobile parts.

You can usually identify the high zinc content if there is writing on the part.

Some of the worst stuff will have good definable letters on it. Because of the high zinc content.

A few time I have welded emblems for an old car because they couldn't find replacements. You have to be real careful not to ruin them, until you find out if they are indeed weldable.

4043 is the rod of choice for me.

Hope this helps someone,

JAckal

Zinc based pot metal can be easily repaired with this product, have used it for many years.

Pot Metal Repair and Restoration

If it's an aluminum alloy these products can be considered.

Muggy Weld Presents: How to Weld Aluminum

I have stick, MIG, TIG, oxyacelylene, oxyhydrogen, furnace brazing and other processes and for certain applications the above products are superior for repair work. I would have used it on this part and it would have been fixed in a few minutes. They and several other Muggy products are always at hand.

No relation to the company, just a satisfied customer.