Discussion in 'Reloading Forum (All Calibers)' started by Webster, Aug 6, 2019.
Yes, and it’s a journey, not a destination.
AMP is in the process of manufacturing/Designing something for measuring seating force accurately and logging it on Arbour Presses. No idea if it is something they intend to sell though.
When you do this you will notice that the first part that begins to glow is the very edge of the case mouth. Very shortly afterwards the glow shoots down the neck towards the shoulder. If you use 750F Tempilaq and dial in a time long enough for it to change colour one shoulder length below the shoulder/body junction you can be very well assured the neck region has gotten a LOT hotter. And so the question is just how far down the case body do you want your 750F indicator to change colour.
Just out of interest, when they manufacture a brass cartridge is the body of the case deliberately hardened to cope with the pressure of firing or is it just incidental and then the necks are softened by annealing for marketing / reloading reasons. Q. Can correctly annealed brass cartridge sustain firing in a chamber or is the brass to soft.
I already have a hydro seater to accurately measure seating force. I would like to see AMP come up with a way to truly put the case back to the same hardness level each time it is annealed.
The brass below the shoulder is intentionally hard. If you anneal it, it will not survive firing. I'm going from memory here, so these numbers may be slightly off, but hard brass has a strength of about 80ksi, where annealed brass is closer to 20ksi. It's a huge difference.
See here for AMP’s findings.
Their annealer already sets the brass back to the same hardness each time.
Hi SGK I found exactly the same thing. However I went on from this point experimenting as I had some 308 brass that had heads that had expanded to much. The changes I made were the seating depth in the coil. I always was under the assumption that the part I wanted to heat should be near the middle of the coil or just slightly higher.
I started inserting the case further and further I was concerned that I may heat the body of the case too much. I ended up with the top of the neck level with the to of the coil or slightly over. I hac concerns that this may be heating the case too much, keeping a close eye on it and using Temilaq this didnt happen. The annealing time went up slightly but the overheating of the neck also didnt happen as pronounced and I go a good annealing temperature in the shoulder area as well as the neck.
If you have some spare brass its worth an hour or two playing around. I also took some cases to melting point keeping an eye on the current draw to see if i could draw any conclusions from that, like the Aztec mode of the AMP.
Yeah, Aztec mode watches for the exact moment the brass melts. Coincidentally, I have melted pieces of .223 rem brass just playing around with my GinaErick Annealer and the current drops right as the brass melts. I'm quite certain that current drop is the same thing that Aztek mode is programmed to watch while analyzing the brass. Aztek then takes the timing and then backs off using some formula they have developed.
So true and worthy of a thread of its own.
This is interesting, and shows just how hard it is to measure inputs when annealing. Based on this description, they're is using an indirect way to calculate heat transfer (current and time) rather than measure temperature and time, as I'm sure they would if they could. It's clever, and impressive to the extent that it works (I don't own one, so I can't say, but I don't have any reason to doubt them).
To be precise, they’re not really calculating heat transfer. Induction heating doesn’t transfer heat. The heat comes from the alternating currents induced in the object. What varies is the “reluctance” of the object and this value is dependent on composition and form of the object a current is to be induced. This is why case wall thickness and it’s distribution requires different programs between cases of the same caliber but different makes.
The body is harder because of the extreme extrusion from a disc to a cylinder. Process annealing means to anneal only enough that the part won't crack in the next forming step. Final anneal necks and a little in the shoulder area.
Amps looks like they are determining what they call a proper anneal by measuring hardness. If you measure harness you don't need to know the temp. In an induction annealer as we make them you normally cannot change reluctance. When you get the hardness you want you record the time to get the hardness. This becomes the time setting to anneal a given type of cartridge. If you cannot measure hardness or have a manufacturer provided setup I would look for a hint of red it a dark room and cut back 10%. This should give an anneal or stress relief or what ever you want to call it. Several technical reports on this website show no grain growth at any times we use with a torch or induction annealer.
AMP has done countless hardness test, per them saying this, to get the right math formula when backing off of the brasses melting point. It’s also worth noting that each pilot has a certain “tuning” in the Aztec software that affects the formula.
I very much doubt AMP's AZTEC mode is measuring hardness at all. I also doubt it is monitoring temp.
"A hint of red it a dark room" [sic] is simply too vague. Plus it is difficult to observe as the time from no glow to it shooting down the neck of the case is a matter of fractions of a second. Peering down into the work coil doesn't provide good visibility either. Tempilaq is a better indicator - the question is just how far down do you want to hit 750F and just what temp (thinner) points above get.
Inductive forces are at their maximum in the centre of the work coil. I have placed the point where the shoulder meets the case body at this mid point. Arguably the case could be a fraction higher - about half the distance between that point and the shoulder/neck junction. There's a limit, however, to how far up the coil I can go as shelf meets coil.
If I get a chance I will try your suggestion.
If I could be really bothered I would look into different coil structures, ones that concentrate the heating to a more localised area. A 1 1/4" "conventional" work coil, while easy to make, is likely not ideal for these purposes.
No one have thoughts regarding AMP's conclusions re cleaning brass?
(I should go visit these guys next time I am back home.)
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