Bob et al
Most people just ream the electrode hole in the disc and use a single grub in the periphery of the disc that then bears down onto the Tungsten. This may work in a G10 resin disc, but not wishing to have a pile of blunt tool bits and a lung infection afterwards, I have always used Tufnol as the material for discs.
Tufnol being a softer material than G10 for threading meant I used the method below. Note: my coiling partner however uses the single grub screw in the periphery on his Tufnol disc to no ill effect (0.5 inch Tungsten's in his case)
See https://www.flickr.com/photos/33962508@N03/24183190853/in/dateposted-public/ to make sence of below:
The "Threaded Stud" is 0.5" stock brass rod, drilled and reamed to accept the 0.25" Tungsten TIG rods and then threaded on the outside to accept the brass nuts made from Hex brass bar. The hex brass bar nuts were cut with a tap, while the Stud was threaded in the lathe, so that it was a slop free fit with the nuts.
Washers sit in between the nuts and the Tufnol disc. Once all is tightened up, holes are drilled right through both the nuts and stud into the central hole. These are threaded for grub screws (fine thread) that not only tighten down onto the tungsten but also now locks the nuts from unscrewing.
Upsides:
Changing electrodes is simply a case of undoing the two grub screws. Very little chance of coming out, and a clash (happened once through stupidity) just breaks the electrode itself, rather than have pulled it out and possibly splitting the disc, as a rim mounted single grub screw might.
Downsides:
Because the tapped hole for the grub goes through both nut and stud it means that they can only be re-cycled onto a disc that's exactly the same thickness though. In the unlikely event that you had to remove and replace on the same disc, it is possible if you mark nut & stud & disc positions with a sharpie first of all, so all goes back in alignment afterwards.
I personally like the method and have used it on three Srsg discs now (a 200 bps normal disc & a 200 bps staggered & 300 bps staggered)
I also grind the revolving electrodes exactly the same length (to with a thou actually) Not because I'm a pedantic Brit nutcase, but it means if the disc wobbles a bit it doesn't matter for the gapping.
Exaggerated example: if a disc had a 1/8 inch wobble at one point, then if the electrode at that point was slid 1/8 inch the other way in its holder to compensate then the gaps will all still be the same in respect to the fixed ones as their flying lengths are all equal.
Also adjustment is easier with exact length flying electrodes. Initial setup means tightening the position of one of the fixed ones, and with a feeler gauge in the gap and all the flying grub screws loose, just push the flying ones through their holders till they contact the gauge and then tighten them. Once all the flying ones are gapped they shouldn't need touching, as ablation then is taken care of by just adjusting a static one, as if one gap is right, then #assuming# even wear on all, then the rest will be correct as well.
## Different firing rates on a Srsg may produce uneven ablation though, while an Arsg "should" ablate evenly by the law of averages.
Phew!
Regards
Phil Tuck
www.hvtesla.com
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of robert massa
Sent: 03 February 2016 15:32
To: Tesla Coil Mailing List
Subject: Re: [TCML] Copper / Tungsten Electrodes
Phil, All
I bought 1/4"x 20" pure tungsten $ 60 , from Midwest Tungsten, here in the states. Used a lot of dremmel cut off wheels to get a 8" propeller with 4 stationary contacts that are 1/4x1" mounted in aluminum holders. Scored the stock about 2/3 and broke seemed to work for me. Used my green wheel to round the edges, but think next time will let nature do it. Very pleased with the run time before adjusting. This is small coil , 900w power supply .
Building a new larger, 1.5hp or 3 hp, robust rotary and would like to know how you made your inserts/holders in your rsg disk . Have lathe and mill. Any advice would be appreciated . Have been looking at pics of other TC's and would really appreciate any suggestions.
Bob Massa
On Thursday, January 21, 2016 4:22 PM, Phil <pip@xxxxxxxxxxx> wrote:
Has anyone had experience of the 90% Tungsten rods, as opposed to the 70%
that I'm currently using?
(90% IS available apparently)
I thinking of its ability to cut with a hacksaw or ordinary cutting disc and
even machine, if anyone has had cause to.
Regards
Phil Tuck
www.hvtesla.com
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla