Re: Machining / Lathe questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Captain,

At 01:49 PM 3/19/2003 -0500, you wrote:

>Just a few questions regarding machining . . .
>
>1.  My first question is that I want to drill and tap a large number of 1"
>steel spheres which I am going to using as
>corona balls (spark gaps actually).

Note that page 2007 of the McMaster Carr on-line catalog (just search on 
"2007") has these.  Steel, aluminum, brass, stainless...  Pre-threaded and 
ready to go.  The steel ones go for only $3.00 each!  The expensive 
stainless steel ones for $6.  These are the knobs you see on heavy earth 
moving equipment controls.  Best to just buy them and unless you really do 
"want" to drill and tap....

www.mcmaster-dot-com

>Anyone have suggestions on how to clamp
>these spheres properly.  I guess the proper way to do this to ensure proper
>centering would be to use a lathe (see next question), but precision isn't a
>hard requirement as they are only going to be used for spark gap balls.  I
>was thinking maybe taking some material putting perpindicular V-Slots and
>having the sphere rest in the intersection point.

Three jaw lathe chuck with covered jaws to prevent scratching.  You could 
heat the balls and melt cup holder jaws in some plastic too.  You want to 
avoid "point contact" but rather have a somewhat large area contacting the 
part you are holding.  Maybe just polypropylene block (thick) would mush 
when in a vise to grab them (but not goof for heat).  Maybe like 3/4 inch 
holes would provide nice holding cups.

Of course, if the pre-made ones above will work, your all set.  If they are 
not right, I would change the other stuff so they will work.  Drilling and 
taping spheres is pretty nasty.  Just the cost of the good taps will far 
outrun the cost of the knobs.

I assume you are "not" thinking of drilling big 'ball bearings' ;-))  I 
have tried that and I actually do use ball bearings for the safety gap on 
my big coil.

http://hot-streamer-dot-com/TeslaCoils/MyCoils/BigCoil/protection.jpg

But those are flattened with a mill file and soldered.  Ball bearing steel 
is harder than most drill bits and will just smear a normal drill.  The 
problem is ball bearings are super hard steel and drilling (let alone 
taping) is "hard".  The cost of the cobalt bits will again set you back 
$$.  I am not sure one can tap such materials at the amateur level.  The 
torques and heat generated is also considerable, so our plastic vise jaws 
may not work...  Prolly just want to by those nice pre-made knobs ;-))


>2.  Secondly, I'm finding that lathe work is becoming a requirement on
>almost all my new tesla and high voltage projects (as well as others) and
>I'm finding the very high prices of out-of-house machining to be very
>restrictive so I think its in my best interest to invest in a lathe and
>start practicing.  Are there any lathes out there for under $500.00 that
>would be okay for practicing and would be tabletop sized (not a huge floor
>mounted lathe)???

I have a Sherline milling machine I really like.  They are very high 
quality and small enough to pick up with one arm (but use two).  You will 
not be able to work on engine blocks or anything big, but for small things 
like about the size of one's fist and lower they are great.  Sherline also 
makes small lathes of the same style.

www.sherline-dot-com

http://hot-streamer-dot-com/sherline/MeanLooking.jpg

http://hot-streamer-dot-com/sherline/P3190015.jpg

These only weight about 50 pounds with toys attached and can easily be 
stored or moved to the kitchen table when needed (having a milling machine 
3 feet away all the time is very nice!!).  You will note the Hot-streamer 
computer and the stereo speaker (get a good little shop vac!).  I probably 
have spent far more on DROs, turn tables, measuring stuff.... than the 
machine itself.  I just get the lathe chuck (fits the milling machine fine 
since most Sherline stuff fits all even if it was not "meant to fit") and 
"fake it" when I need to turn something.  Sherline also has many many 
accessories like DROs and CNC attachments).  I need milling capability for 
coil work and other machining intensive projects:

http://hot-streamer-dot-com/Ti-Tan!!/

There are a number of China made milling machines and lathes for your price 
too.  These are sort of "kit/projects" in they work well enough that you 
can use the machine to fix the machine ;-))  As this and that snaps off, 
you can make new parts for it ;o))  Harbor freight and other "fine" 
importers carry such things, but Grizzly is probably the best place to get 
the China made machines.  Grizzly makes sure the quality is fair and that 
the hand wheels are not 63.5 mil/turn (guess how that happens ;-))*

www.grizzly-dot-com

# G8688 and G4000 are typical.  Note the shipping weights...

Of course, there is Ebay for these and other items too.  Sherline and 
Harbor Freight have the manuals on-line...

*They put a hand wheel marked in 0.001inches on a metric lead screw :-p

Cheers,

         Terry

BTW - Yes!, it did snow 32" here :o))

http://hot-streamer-dot-com/temp/MySnowCar3-19-03.jpg

Tore DIA's pretty roof :-(







>Any help appreciated.  Thanks.
>
>The Captain