Post by fishhawk on Jan 19, 2017 11:23:47 GMT -5
I use 2 different materials. The first I used is Tungsten carbide. This is 90% Tungsten with 10% Cobalt as a bonding agent. This is very likely what many are referring to as carbide. I am only making bushings I sell directly for several months now. What anyone else call theirs I can't control. I believe this is powdered Tungsten and Cobalt powder sintered together with heat and pressure. This is sometimes referred to as 90/10. These are what Richard first tested for me in a 209 gun. These were lasting 300 and more shots with the loads we were shooting at the time. As far as I know, none of these bushings have ever cracked. Any of these Tungsten Carbide bushings I made were EDM drilled only. This means that the hole of a new bushing will have a thin coating of copper and slag from the electrode caused by the single polarity of the EDM drill. So, a new Tungsten carbide bushing will wear a couple thousandths of the copper/slag out with the first few shots. Because the EDM drill electrode used is a hollow tube of .025" copper in a guide the spinning electrode can wobble more or less with each bushing drilled. So, when you check the hole in a new .030" target bushing, it will measure .028"- .030". After shot a few times they should be .030"- .032". I believe these wear due to the bonding Cobalt burning away taking to Tungsten with it To identify Tungsten carbide bushings I make, the ends of the bushing will have a sharp edge.
When Earnhardt from the other board started pushing his .416 with 120gr and more of Retumbo and 325-350gr bullets, Tungsten carbide bushings would burn several thousandths in 15 shots or less. So we looked for a material that would burn out less, this is where pure Tungsten came in. This is 99.95% Tungsten powder that is also sintered together. Tungsten bushings burn away much slower that the first material when shot. The only flaw with pure Tungsten is they will split due to pressure, pocket size, vent hole diameter, and the fact they are very brittle. When EDM drilling these it took three times the time and electrode to make a hole. Bushings of .030" and less were EDM drilled to a smaller hole size and all sizes were finished on a WIRE EDM for perfect hole size and no slag due to the dual polarity of the wire EDM machine. The reason for this was originally wanting perfect size hole to regulate pressure to the primer on the high pressure sub calibers that pure Tungsten bushings were developed for. Pure Tungsten bushings I make are identified by a small bevel on the ends where the first material ones are sharp.
In my opinion, the only guns that that need pure Tungsten bushings are ones that can burn out a Tungsten carbide bushing too fast. Way to many people wanted pure Tungsten before enough testing was done, and my statement that their gun likely didn't need them based on caliber and load.
For Jeffs HIS, I think only Tungsten Carbide is needed due to smaller volume flame path between primer and bushing. But I could be wrong on certain applications such as Cyclops or even my .375.
When Earnhardt from the other board started pushing his .416 with 120gr and more of Retumbo and 325-350gr bullets, Tungsten carbide bushings would burn several thousandths in 15 shots or less. So we looked for a material that would burn out less, this is where pure Tungsten came in. This is 99.95% Tungsten powder that is also sintered together. Tungsten bushings burn away much slower that the first material when shot. The only flaw with pure Tungsten is they will split due to pressure, pocket size, vent hole diameter, and the fact they are very brittle. When EDM drilling these it took three times the time and electrode to make a hole. Bushings of .030" and less were EDM drilled to a smaller hole size and all sizes were finished on a WIRE EDM for perfect hole size and no slag due to the dual polarity of the wire EDM machine. The reason for this was originally wanting perfect size hole to regulate pressure to the primer on the high pressure sub calibers that pure Tungsten bushings were developed for. Pure Tungsten bushings I make are identified by a small bevel on the ends where the first material ones are sharp.
In my opinion, the only guns that that need pure Tungsten bushings are ones that can burn out a Tungsten carbide bushing too fast. Way to many people wanted pure Tungsten before enough testing was done, and my statement that their gun likely didn't need them based on caliber and load.
For Jeffs HIS, I think only Tungsten Carbide is needed due to smaller volume flame path between primer and bushing. But I could be wrong on certain applications such as Cyclops or even my .375.
