Drilling razor blade with pencil sparks?

[superUnknown]

Is this even possible? BS?

[robrenz]

Bad link, but yes using the pencil as a graphite electrode in an edm machine will easily drill thru the razor blade.

[superUnknown]

sorry. BBcodes. working now.

[deth502]

not only can you, but it is much, much, much easier than what you saw in the video. i made a small homemede one to burn out a broken tap with 2 light bulbs as a ballast, 2 large caps, and very little else. i used a brass tube as the electrode.

[deth502]

something like this:



only iirc, i had 2 100w bulbs in there, no resistors, no meters. you can estimate the current draw by the light from one of the bulbs and used that as you "meter" and no variac. amof, i dont recall using a transformer. went right from the wall to the rectifier.

[Fraser]

If this is like 'spark erosion', I recall my Father showing me how the internal cooling channels were cut into titanium gas turbine engine blades at Rolls Royce (Aero Engines) in Bristol. The tubes extend up through the blade from the root to tip AND from these channels through the blade to its leading and trailing trailing edges. I was amazed that the process was capable of accurately cutting the cooling tubes within a curved surface, following the centre line of the blade. Clever stuff.

I attach pictures of one of my Gas Turbine Engine blades given to me by my Father when I was a youngster. Its an HP Compressor blade from an RB199, Olympus or Pegasus Engine..... I can't recall which. I always loved the Pegasus that is used in the BAe Harrier so it may well be from that Engine. I also have the LP blades from such engines. They are much larger and do not need the cooling channels. The HP compressor blades would melt without such cooling. How the tubes were cut used to be an Industrial Secret.
 

[superUnknown]

Those blades are incredible! No doubt done with a No2 pencil?

[Fraser]

I didn't provide a scale indicator in my pictures 

The holes are truly tiny diameter. The blade is only approx. 2 inches (50mm) long !

[superUnknown]

only iirc, i had 2 100w bulbs in there, no resistors, no meters. you can estimate the current draw by the light from one of the bulbs and used that as you "meter" and no variac. amof, i dont recall using a transformer. went right from the wall to the rectifier.

So would that spark at mains frequency (60Hz) or much faster because of large caps? How fast?

[deth502]

it had a "bacon sizzling" sound to it. so, yeah, probably about 60 hz.

im surprised no one mentioned it, and yes, i will agree that it was as unsafe as shit, but it was a quick and dirty solution to get a hardened tap out of a piece of aluminum that already had too much machining time into it to scrap, and safety precautions were taken.

another thing is its usually done using a dielectric fluid of some sort. i just used water for mine, which will create hydrogen, which is explosive. again, not the safest, but follow a few safety precautions, like only using in a well ventilated area, chances of things going awry can be greatly reduced.

[deth502]

ok, i give up. spent at least an hr looking for the article. i thought it was a popular mechanics article, but it turns out it was more likely a popular science article. they have a "complete archive" online, i found some reference to it in the march 1968 issue on page 149, but their "complete" archive jumps from page 148 to 155.

[macboy]

ok, i give up. spent at least an hr looking for the article. i thought it was a popular mechanics article, but it turns out it was more likely a popular science article. they have a "complete archive" online, i found some reference to it in the march 1968 issue on page 149, but their "complete" archive jumps from page 148 to 155.

That's probably because the article on page 149 is extremely dangerous!