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| snapped centre drill |
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| tomfilery:
Andrew, I don't know why it should be! I'd guess you use a saturated solution for rust removal - as I do for drill removal. I usually heat the acid liquid in the microwave for around 30 seconds - but, apart from speed of reaction, I can't suggest why the steel should get eaten away in one application and not in the other. Might it be electrolytic - in that with two dissimilar metals in the acid (in my case brass and steel) the steel becomes sacrificial? Regards Tom |
| Arbalist:
Citric acid will dissolve steel, it's just a matter of how strong the solution is to how quickly it does it. I've tried using it for rust removal but never again as it leaves the surface looking a very dull grey. I use washing soda and a battery charger as it doesn't attack the surface of the steel at all, it just loosens the rust. |
| awemawson:
Odd isn't it - I've used it for years and have never noticed any dissolving of the steel. In the case of brass I would be concerned that it might de-zincify it, as happens to under ground brass water fittings that eventually become porous. When I rebuilt my 60 ton EPCO press, it had been in a bad fire then left in the open for several years, and the four 1.5" steel acme threaded platen raising screws were solidly rusted into their bronze nuts. I was able to rise the platen with the fork lift leaving the huge bronze nuts low down, then put each in a bucket of citric acid that was saturated, initially hot, and regularly changed over ultimately about five weeks before they were all freed. Then I was able to remove each screw and further soak them for days on end in citric acid in a length of 110 mm soil pipe bunged at one end. Despite having been in the citric acid for best part of two months those acme screws still fit nicely on the nuts and are now in use. |
| S. Heslop:
One place i've found alum and citric acid at is halal food stores. They of course usually have great selections of spices, and alum is usually included in that since it's got some food uses. |
| porker:
I'm learning stuff here so that is good. Why is it that I seldom see spotting drills for sale (at least in places I go in the UK)? I don't think Arc carry them for instance. |
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