Steel screw removal using alum - follow-up

Your problem is "room temperature" and the wrong alum. In my response to the first poster to ask this question I said a saturated solution of alum (meaning no more will dissolve in near boiling water) and keep it close to boiling. If it is a plain steel screw or carbon steel tap it will fall out in a few hours. Stainless takes a couple of days but the solution has to be HOT.

Also use regular pickling alum from the grocery store. Potash alum is not the same thing.

OK Glenn, I give up. What is pickling alum that you buy in a grocery store? Steve

It should be Ammonium Aluminum Sulphate (as opposed to Potassium Aluminum Sulphate).

YMMV, though.

Go to the grocery store and find the spice rack. If it is laid alphabetically out like Kroger or Publix it will be in the upper left corner of the store brand section. Fine white powder in those little 2.75oz spice bottles. Buy a couple of bottles to dissolve in a quart of almost boiling water water.

Ummm.

However, as true RCMers we should:

I am ignorant of chemistry. Is it the sulfuric acid in the compound that is actually doing the work, with aluminum's oxide layer protecting the workpiece?

Kevin Gallimore

I wonder if the white metal in the original experiment contaminated your solution with zinc. I would suggest the following:

1: Get a new bottle of alum from the spice department at Tesco 2: If possible, drill a hole thru or at least into the steel screw 3: See if you can insert a steel wire in the hole in the screw, in the alum solution, with the wire not touching the metal 4: Apply low-voltage DC, 1.5 to 3 volts, with negative to the wire and positive to the part to be removed.

This worked for me when I had a steel bolt broken off in a VW block. Took about 3 days, but it worked. If you can't get a hole into the screw, try centering the wire just above the screw. This will be slower because it has only the end of the screw to work on.

In my case, I did not immerse the whole works but built a little dam around the site with modelling clay and filled the resulting puddle with alum solution.

I'm sure Don means "with the wire not touching the aluminum". I did this very thing absent the electrolysis factor, but I added a wrinkle: I put a drop light with a 100 watt bulb right next to the hole and put a No. 10 can over it, so it kept the whole area at least warm to the touch. I let the alum run for two weeks, screw is happily still in there. Next time I'll try Don's excellent idea. After that, I tried nitric acid, also in a small circular dam of clay. I think maybe my clay was some kind that reacts to the acid, because after quite a short time it seemed to stop acting.

The screw I was dealing with was self-tapping, extremely resistant to drilling. Pretty much a nightmare to get out. In the end, I got 4 of the 5 broken screws out of my casting, all with easy-outs.

GWE

The acid does need refreshing as it gets used up. This is about the only advantage of being a diabetic. I have more little disposable syringes with

3/8" 30SWG needles than I know what to do with. They are quite handy for squirting fresh chemicals down screw holes.

Mark Rand RTFM

You can also get cheap disposable syringes & needles at any farmers co-op.

Lotta diabetics reuse each needle many times until it gets dull. Sure beats those giant sharps containers ..

GWE

So do I. But even using them until they get blunt (hooked is worse, they don't hurt until you pull them out), you can build up quite a collection over 40 years or so.

Mark Rand RTFM

I still have a couple of the old, ground glass syringes, along with the big white tray used to sterilize cotton wrapped packages of instruments etc. in the oven of the old, wood fired, cook stove. These items from my Mother who was a Public Health Nurse a day's journey from the nearest doctor (Electricity came to the area in 1948). In latter years, she used to bring large, seized syringes home because I had a particular amount of luck in freeing them up, saving the outpost hospital the cost of replacement. On a couple of occasions, procedures were delayed a day waiting for me to refurbish equipment. Gerry :-)} London, Canada

When blackening brass, I use a UV-lamp for plant growing to heat it up.

Nick

Still no luck at room temperature. I've heated the part up quite a few times, but I don't want to leave it simmering unattended because the water needs topping up often. At room temperature the alum doesn't seem to have had any effect on the steel screw (apart from turning it black). Maybe I should trying keeping it warm (we have an old slow cooker), or maybe I have the wrong kind of alum, but the signs really aren't hopeful. I'm going to start looking for nitric acid.

My gut reaction is that this isn't an easy-out job. The screw broke because it was rusted tight, so my guess is that the easy-out will break too, resulting in me being totally screwed!

Best wishes,

Chris

Funnily enough I have a mountain of those syringes for exactly the same reason. Might come in handy if I can find some nitric acid.

I also discovered while in high school that the syringes can be made into single-use dart guns, but I seriously don't recommend trying this. If you dip the needle in epoxy to seal the hole, or gum it up with blu-tack, then when you depress the plunger the end cap (which is a tight interference fit on the syringe) leaves at a very high velocity :-D.

Best wishes,

Chris

I know you don't have the NHS over there to absorb your sharps containers, but surely you've got a backhoe, right? :-D

Chris

If you can drill the hole you would need for the easy-out, it would help any chemical approach. If you get esoteric and find a supplier for left handed drill bits in the size you need that doesn't charge 3 arms and 5 legs for them (and require you to buy a gross at a time) the act of drilling it out _might_ just help to break it free. But it's a pain for a small screw, to be sure. Still , the heat of drilling, and the access to be back-side of the drilled out screw, and the turning out with a left-hand drill if you can find one (or a rh drill for a lh threaded broken screw) would all help, without ever getting to the point of putting the easy-out in.

Back in the good old days (mid '60s until late '70s), when I used glass syringes and leur taper fitting stainless needles, I found that out more than once. Take the syringe out of the industrial spirit, fit the needle on it, pump the syringe to clear all the alcohol out of it...

Damn the bloody needle's blocked with a bit of skin or dried insulin and has blown off and stuck in the carpet/my foot.

On the other hand, industrial spirit is ideal for Mamod steam engines. I think I used far more of it for that than for keeping needles and syringes sterile :-)

Mark Rand RTFM

Air cooled VW is not aluminum . I TIG welded a case , had to go back to weld store for magnesium/aluminum rod , which worked fine.

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