Edwards Radial 5 build thread --- PHOTOS!

I tried this with fuming nitric acid and failed! The tap did not dissolve in 18 hours. I am thinking the reason it failed was a coating of oil on the tap? If you try this method I would irrigate with acetone or other volatile cleaner first, then apply the acid. Please let us know your results.
Robert
 
A coating of oil will prevent or at least slow the acid from ever touching the metal.

Watch where you buy you nitric acid, there are a lot of places that sell "nitric acid" but it is only 0.01% acid and 99.99% water, not much use for anything. You want at least 67% acid.
 
Build your self a small simple edm.
Its slow but works so well you never fear breaking a tap again.
There are far better versions available than this one but for approx $12 it actually works.
www.hobby-machinist.com

Keyed Washer/spacer

I need to make one of these 50mm outside dia, 12mm inside dia, 4mm thick, the tab 5mm across, all in stainless steel. It has to be very flat on both sides with no warping. The only way I can think of is to cut a key way and braze the tab in then smooth it out. But.... I dont trust my brazing...
www.hobby-machinist.com www.hobby-machinist.com
 
savarin said:
Build your self a small simple edm.
Its slow but works so well you never fear breaking a tap again.
There are far better versions available than this one but for approx $12 it actually works.
www.hobby-machinist.com

Keyed Washer/spacer

I need to make one of these 50mm outside dia, 12mm inside dia, 4mm thick, the tab 5mm across, all in stainless steel. It has to be very flat on both sides with no warping. The only way I can think of is to cut a key way and braze the tab in then smooth it out. But.... I dont trust my brazing...
www.hobby-machinist.com www.hobby-machinist.com
Click to expand...

What do you mean by "Kero"?

Eric
 
JRaut said:
Thanks for the good info, Jerry.

If still got my old crankcase with the tap still embedded. So maybe if I can get my hands on some nitric acid I can give it a whirl.

Any idea if any household products would do the trick as well, albeit slower? I haven’t tried googling around at all, but I don’t have any obvious connections for acquiring potent acids.
Click to expand...
I don't know of other products which would achieve the result you want.

First, you DO NOT WANT fuming nitric acid. I think a simple 10/20% solution at most is all that you need, the kind of concentration used in school laboratories. It is the oxide coating on the aluminium which protects it from the acid. If you use sulphuric (battery acid) or hydrochloric acid (brick cleaner) you may well dissolve the oxide layer and attack the aluminium. By all means flush first with an oil solvent but I do not remember having done so myself. It took me maybe 3 days of filling, flushing, refilling with acid before the tap had just disappeared. I expected a bit to drop out but there was nothing left.

Drug stores (Chemists we call 'em) used to keep chemicals of this sort but not in the UK any more I suspect - elf n safety don't you know. I found 3% nitric for sale on the net. That will still dissolve the steel but may just be slower.
 
rwm said:
I tried this with fuming nitric acid and failed! The tap did not dissolve in 18 hours. I am thinking the reason it failed was a coating of oil on the tap? If you try this method I would irrigate with acetone or other volatile cleaner first, then apply the acid. Please let us know your results.
Robert
Click to expand...
No, it was because the acid was concentrated, there was nothing for the iron to dissolve into. It needs the water present for the ferric ions to swim about in :)
 
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