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    Threading tungsten carbide rod

    Will a high speed steel or a carbon steel die be able to put threads onto a 3mm tungsten carbide rod?

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    Re: Threading tungsten carbide rod

    Expect the die's tiny teeth to break on tungsten carbide.

    You might manage to cut a thread on a lathe with diamond-tipped tool. Set the carriage to move one thread per revolution. Expect it to require many passes.

    What about using an ordinary machine screw? A welding shop ought to be able to attach your tungsten carbide piece. It is similar to renewing a lawnmower blade by welding a bead of tungsten carbide along the edge, then sharpening it on a grinding stone.

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    Re: Threading tungsten carbide rod

    Will a high speed steel or a carbon steel die be able to put thread...
    The short answer is no.

    These rods are made by sintering from powders. They are extremely brittle. You can perhaps drill a hole using a spark erosion machine but I do not see how you can cut a thread (outside or inside).

    But even if you somehow manage to make a thread onto the rod, it is likely to have poor mechanical strength because of the brittleness of the material.

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    Re: Threading tungsten carbide rod

    What are those rings with a screw built in which can be used to torque the ring and anything inside and in between the ring?

    https://www.ebay.com/itm/202251444918

    Does that listing depict what appears to be a sintered tungsten carbide piece?

    Perhaps I should use nickel rods over tungsten carbide since they both perform well in spark gap applications.

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    Re: Threading tungsten carbide rod

    I'd look for another attachment method. Such as build
    up some brazing and thread -that- (if the attach point
    doesn't have to take much temperature, which why
    should it?).

    Why tungsten carbide rather than tungsten welding
    rods? You can probably find collets that match at the
    same welding supplies place, meant for tens of amps
    to hundreds of amps welding current.

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    Re: Threading tungsten carbide rod

    Collets appear to be the ideal implementation for this. Many appear to be solderable directly with ordinary 60/40 lead type which removes the burden of fasteners and torquing the same.

    The welding rods are far less expensive coming in quantities surpassing the necessity for a spark gap and swapping eroded parts should be simple with collets. But how do those welding rods compare against nickel rods?

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    Re: Threading tungsten carbide rod

    nickel rods over tungsten carbide since they both perform well in spark gap applications...
    You did not say that you are going to use them for spark gap applications.

    If you want lower arcing voltage, use a pointed rod (tungsten is ok but not the carbide) and expect the point to wear away with continuous use. Tungsten has a very high melting point but it is not resistant to bombardment with high energy ions...

    If you want a stable discharge, use a rounded tip that may need slightly higher voltage but the life will be longer (discharge arc will start from a random point).

    If you solder a nice round ball to the tip (neat soldering without rough edges is the key) that the material can be anything (copper or aluminium or gold or platinum; make your choice) but the arc will need higher voltage to start.

    The link you pasted in #4 does not work.

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    Re: Threading tungsten carbide rod

    Quote Originally Posted by c_mitra View Post
    You did not say that you are going to use them for spark gap applications.

    If you want lower arcing voltage, use a pointed rod (tungsten is ok but not the carbide) and expect the point to wear away with continuous use. Tungsten has a very high melting point but it is not resistant to bombardment with high energy ions...

    If you want a stable discharge, use a rounded tip that may need slightly higher voltage but the life will be longer (discharge arc will start from a random point).

    If you solder a nice round ball to the tip (neat soldering without rough edges is the key) that the material can be anything (copper or aluminium or gold or platinum; make your choice) but the arc will need higher voltage to start.

    The link you pasted in #4 does not work.

    It needs ~2.5mm-3mm of distance. Seems they use nickel in spark plugs because it will outlast tungsten. Id use spark plugs but surface area for discharge is very small which is why nickel rods seem ideal.

    Nickel can be drilled and threaded unlike tungsten.

    https://www.ebay.com/itm/372654767066/

    Is the mentioned distance with ~0.843 joules per breakover at 80-120hz too much for nickel?
    Last edited by Zak28; 14th May 2019 at 07:29.

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    Re: Threading tungsten carbide rod

    Seems they use nickel in spark plugs because it will outlast tungsten...
    I cannot verify this statement but tungsten is widely used in relay contacts where arcing is expected. You are advised to replace the spark plugs on a regular basis. If the energy is not too much, I would advise carbon rods (they too have a very high melting point).

    - - - Updated - - -

    This link is not working... I get a 404.

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    Re: Threading tungsten carbide rod

    you can buy all kinds of spark gaps and triggered spark gaps
    with all kinds of trigger voltages and current capabilities

    with the advantage of being well known and documented

    what requires you build your own?

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    Re: Threading tungsten carbide rod

    Quote Originally Posted by wwfeldman View Post
    you can buy all kinds of spark gaps and triggered spark gaps
    with all kinds of trigger voltages and current capabilities

    with the advantage of being well known and documented

    what requires you build your own?
    Link https://www.ebay.com/itm/US-Stock-10...d/372654767066

    As far as premade spark gaps - only found spark gap tubes and spark plugs nothing else.
    Last edited by Zak28; 16th May 2019 at 23:02.

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    Re: Threading tungsten carbide rod

    sorry Zak ebay is not a source

    spark gaps are usually cylinders of non-conductive material with an electrode at each end
    the sizes, shapes and gas or vacuum inside determine when they arc over

    triggered gaps act somewhat like SCR - they conduct when gated or if the voltage gets too big

    i have used them from about a centimeter in diameter and 2 centimeters long
    to about 10 cm in diameter and 15 cm long, triggered and triggered

    http://www.teledynereynolds.com/prod...ces/spark-gaps

    https://www.bourns.com/products/swit...rk-gap-devices

    http://www.highenergydevices.com/pro...-electrode%20/

    and there are lots more sources with real engineering information

    what are you thinking you want?

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    Re: Threading tungsten carbide rod

    Bourns has ideal product series but insufficient voltage criterion. The other 2 vendors haven't any online retailers and even the available bourns switching spark tubes have no retailers also. https://www.bourns.com/inventory-sea...ARTS=ST-0350-B

    Seems I must build for myself. This particular spark gap will be for a tesla coil and I would much rather have a premade spark gap. Im likely going to obtain a large gas transient surge protection tube and see how long before it ceases to operate as a spark gap.

    Low voltage switching spark tubes enable low voltage capacitve discharging into a primary side of a high turns ratio transformer which is far safer and yields more current especially with elevated voltages 300-400v the current can be much higher than from pulsed high kv voltage capacitors.
    Last edited by Zak28; 18th May 2019 at 01:17.

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    Re: Threading tungsten carbide rod

    did you look at the EPCOS?

    https://americas.rsdelivers.com/prod...ily=20138&tag=

    what voltage are you looking for?
    what current are you looking to carry?

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    Re: Threading tungsten carbide rod

    That retail site is excellent but those have very limited cycles. Seems only metal spark gap can be used.

    The specific swhiching is for ~8kv @ ~45hz-80hz not sure about peak current since that greatly depends on parasitics but the capacitor bank consists of 2 10kv 13.2nF caps in series, each 10kv 13.2nF cap is 4 ganged 10kv ~3.3nF caps.

    This is the arrangement with 3 spark tubes.





    Can 3x of these https://americas.rsdelivers.com/prod...oltage/7710029 be series attached to yield 9kv breakdown?
    Last edited by Zak28; 18th May 2019 at 02:06.

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    Re: Threading tungsten carbide rod

    Carbon "gouging rods" can probably still be had at
    old-timey welding stores (plasma cutters have about
    done them in, as a tool). They come with a copper
    jacket that can be easily peeled off to expose the
    carbon. You could finish them round or pointed or
    flat, graphite is easy to work. At low current they
    ought to last a good while, the jacket can be (say)
    soldered into the next larger sized brass pipe nipple
    and get some adjustability for gap.

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    Re: Threading tungsten carbide rod

    Wouldn't the carbon spark gap emit loads of dust?

    I have many 100mm x10mm graphite rods they fit nicely inside an evacuated resistor shell https://www.ebay.com/itm/371887176369 which provides heatsinking.

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    Re: Threading tungsten carbide rod

    i expect you can put the three 3000V gaps in series

    look at this - a guy building a tesla coil and a home made spark gap:

    http://lab.dereklow.co/spark-gap-tesla-coil/#sparkgap

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    Re: Threading tungsten carbide rod

    Whats the correct method to obtain nominal current for single discharge with given circuit disregarding reactive parasitics?
    Last edited by Zak28; 18th May 2019 at 03:23.

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    Re: Threading tungsten carbide rod

    please post a complete schematic of your tesla coil

    what is the source voltage?
    what is the turns ratio of the step up transformer?
    what is the nominal spark gap arc over voltage?
    what is the inductance of each resonant coil?

    I expect I am telling you what you already know:
    Tesla coils produce very high voltages at very low currents on output
    the current through the spark gap on the primary is quite high since
    there is only the "parasitic" resistance of the wires and junctions

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