Aluminum Sulfate Use in dissolving HSS?

After searching old newsgroup posts, I found that aluminum sulfate is used
to burn broken HSS taps and drills out of aluminum which is my present need
(drill bit). Low and behold, McMaster stocks it and it arrived today. No
MSDS was included. I've always laughed when MSC will include an MSDS on
cutting tools like taps and end mills, and here McMaster doesn't even
include them on an honest to gosh chemical :) A 3 minute web search turned
up the MSDS, so no problem there.
This stuff comes in powder form. Anyone know what kind of concentration I
need to dissolve the HSS? I can't reach the drill bit by mechanical methods
and I thought I'd learn something new (chemical dissolving) before resorting
to an EDM shop.
Reply to
Loading thread data ...
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.
Reply to
Ken Moffett
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.
Reply to
It is also sold as a flocculent for swimming pools at pool stores, perhaps even Wal-Mart.
Reply to
Richard J Kinch
Thanks Ken, much appreciated.
Reply to
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...
Reply to
Todd Rearick
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.
Reply to
I thought that DejaNews was long gone, and that Google had replaced it.
The principle remains the same.
Enjoy, DoN.
Reply to
DoN. Nichols
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
Reply to

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.