Aluminum Sulfate Use in dissolving HSS?

I've done this several times for both alunimum and copper. The pieces I had were small blocks, so I put them in a 500mL bearker of water on a hotplate (lower than boiling) with about 100mL of alum (aluminum sulfate). I don't think there is a magic ratio for alum to water (more is better ??). The hotplate was the stirring kind so the solution was always moving. I took the part out and rinsed out the hole periodically (once a day). It does take time. Eventually you can tap the piece and what is left of the drill or tap just falls out. When the solution cools the alum crystalizes out, and you can save it for another run.

Aluminum sulphate is about 5$ for a 4lb bag at garden centers. It is used to lower soil pH for blueberries and azaleas. Thread benders might have a source too as it is used to condition fabrics prior to marbelizing. If I was guessing how concentrated to make it I would make a saturated solution and then add a cup of water.

It is also sold as a flocculent for swimming pools at pool stores, perhaps even Wal-Mart.

Thanks Ken, much appreciated.

George

Actually, I read that Aluminum sulphate is not recommended for blueberries because the aluminum can be toxic to the plant. For blueberries you should use Iron or Ammonium sulphate instead. I only know because I just planted bluberry bushes, and I already use Aluminum sulphate to treat my well water (it forces colloidal iron to precipitate out..), and was a little annoyed to find out I can't re-use this for my bushes also...

Todd

Is this the stuff known as "Alum" and available at the grocery store? I think so.

From what I read, dissolve as much as you can in a pot of boiling water (seems like a good idea to use an enamel coated pot) and then throw the parts in for half an hour's simmer. Steel will dissolve, aluminum will stay.

My guess is a dejanews search for this group for the last decade on "alum steel boil" will get you what you need.

I thought that DejaNews was long gone, and that Google had replaced it.

The principle remains the same.

Enjoy, DoN.

The term "alum" is used for a couple of different substances. Grocery store alum is potassium aluminum sulfate. Gardening store alum is aluminum sulfate. Either will probably work for eroding the HSS tap, although I haven't tried.

John Martin