[TheForge] was cutting 1/4 copper now welders

[Steve Smith]

Kevin, Grover, whoever else has plenty of time:

Scientific American magazine used to run a column "The Amateur 
Scientist", which was an amazing experimentalist's column. You name it, 
they did it, mostly from scratch. Lasers, rockets (no manufactured 
engines...), telescopes starting with a porthole, plasma torches, atom 
smashers, ruling engines for making diffraction gratings. Wonderful 
stuff that strongly influenced me growing up.

Did I say plasma torches? Yep. In the early 60's they had a column on 
such. As I recall, the torch was water cooled and was bench mounted 
pointing up. It "vaporized most metals instantly, including tungsten. 
Ceramics took a little while...". I think it would be really tough to 
adapt to a cutting torch (and it would probably have a huge kerf).

If you want to dig into "The Amateur Scientist", all of it from the 
1920's thru the end of the century, it is available on CDROM:
http://www.amazon.com/exec/obidos/ASIN/0970347626/qid=1113521388/sr=2-1/ref=pd_bbs_b_2_1/002-2539502-2820810
Watch out if the URL gets wrapped, you may have to cut and paste a 
second time. Really fine stuff if you're into building and experimenting 
with just about anything.

Steve

Grover Richardson wrote:

> Actually, my interest is work related.  We are doing some work with
> arcs/plasma.  The gas is conductive and will provide a longer arc distance
> than just air.  According to the manual, it will strike an arc easily, so
> that would make sense with the higher Voltage startup.  As I remember, the
> startup arc is ac.  So, essentially (it appears) an arc may be struck at
> most any reasonable distance, and then the operator would move the electrode
> into the proper working distance.
> 
> Me, I'm an old stick person, and never messed with a tig/mig before.  Except
> for repairing a few.
> 
> The welder we are using, TIG, has a arc starting circuit which generates a
> very nice spark plug type arc (bounces around and very thin), which
> initializes the main arc.  I guess I need to look closely at the open
> circuit Voltages.  I need to take the welder apart anyway, to get inside and
> take some measurements.  Will make the startup measurements also.
> 
> I had warned my student about Voltages being dangerous, but now the warning
> will be increased!!
> 
> Thanks.
> 
> -----Original Message-----
> From: theforge-bounces at mailman.qth.net
> [mailto:theforge-bounces at mailman.qth.net] On Behalf Of Steve Smith
> Sent: Wednesday, April 13, 2005 9:47 PM
> To: Sponsored by ABANA
> Subject: Re: [TheForge] cutting 1/4 copper
> 
> 
> On top of that you need a higher open circuit voltage to strike the arc. 
> 300V comes to mind, but I don't know where from.
> 
> Steve
> 
> Grover Richardson wrote:
> 
>>Hmmm.  140 VDC, 40 Amps.  That's enough to fry a monkey.  I didn't 
>>know it was anywhere near that high.
>>
>>-----Original Message-----
>>From: theforge-bounces at mailman.qth.net 
>>[mailto:theforge-bounces at mailman.qth.net] On Behalf Of Kevin D
>>Sent: Wednesday, April 13, 2005 12:11 PM
>>To: Sponsored by ABANA
>>Subject: RE: [TheForge] cutting 1/4 copper
>>
>>
>>Grover,
>>
>>Just looked this up on; http://store.cyberweld.com/milspec625.html  
>>for a MILLER SPECTRUM 625 PLASMA CUTTER
>>
>>
>>Quick Specs: Spectrum 625
>>Rated Cutting Capacity Rated: 1/2 in (13 mm)
>>Quality: 5/8 in (16 mm)
>>Sever: 7/8 in (22 mm)
>>Rated Output 40 A at 140 VDC, 50% duty cycle at 40? C / 104? F Plasma 
>>Gas Flow/Pressure 6 CFM at 75 PSI or 170L/min at 517 kPa Weight Net: 
>>57 lb (26
>>kg)
>>Ship: 60 lb (27 kg)
>>
>>Kevin
>> 
>>
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> 
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