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Topic: Metered arbor press bullet seating question (Read 110 times) previous topic - next topic

Metered arbor press bullet seating question

I'm very close to digitizing the K & M Powerpack and am hoping for some feedback from those members who've used ANY metered press.

Obviously an analog gage like a dial indicator, offers no way to show the operator a reading history over time, well, I suppose a video capture would make that possible, if not awkward.

My assumption is the force curve for a typical bullet seating operation starts from a nominal value, steadily climbs as more bullet enters neck, then levels off briefly depending on bearing surface lengths of the bullet and neck, and finally goes off the chart once the die bottoms out.

My question is, what do you "capture" from the gage reading that tells you what you want to know about the seating operation?

Chris

Re: Metered arbor press bullet seating question

Reply #1
Pressure required to initiate bullet seating (first stage of entry). Slope of the seating curve and peak pressure of that curve.  Slope of the curve requires a constant and consistent movement of the bullet - IE. mm/Sec or something of that nature.

Re: Metered arbor press bullet seating question

Reply #2
Pressure required to initiate bullet seating (first stage of entry). Slope of the seating curve and peak pressure of that curve.  Slope of the curve requires a constant and consistent movement of the bullet - IE. mm/Sec or something of that nature.

Is that what you get now from the dial indicator, of what you would like to get?
Chris

Re: Metered arbor press bullet seating question

Reply #3
Indicator gives starting and peak pressure reliably. The actual pressure curve beginning to end is a group of measurements over time and thus is only comparable with a constant rate of bullet movement - were now talking about the AMP ram on their new press.  You can not consistently accomplish this manually but with practice you can come close. When you do, you can begin to visualize a curve based on gauge needle movement thru the seating stroke. I don’t think you could visualize this as easily using a digital readout. Regardless of the type of indicator, you don’t get a graphed recording to compare with multiple other seatings.

Re: Metered arbor press bullet seating question

Reply #4
Chris, my opinion regarding visualizing a curve on an analog versus digital meter is probably not objective. I don’t use a digital meter so I actually don’t know.

Re: Metered arbor press bullet seating question

Reply #5
Thanks Jerry, that makes perfect sense.

What I've been working on, when I say "digitize", is to capture real-time readings from a suitably equipped gage. And, when I say "real-time" I mean sampled. Sampling is the best we can hope for when doing analog to digital conversions, we just need the sample rate to be sufficiently fast to make it analog-like. Video recording uses frames per second to describe their sampling rate, the higher the better of course, but at some point, the rate is sufficiently fast that the human eye sees fluid motion.

What I'm hoping for is to capture a continuous stream of readings from a suitably-equipped indicator, maybe as many as 30 per second, then turn that into a force-over-time graph. How the indicator's display works won't matter, it could even be disabled or disconnected. All I want from the gage are the readings; I already know the time they're received. In perspective, if I can stream readings at 30 per second for a stroke that may last 2 or 3 seconds, that's only 100 or so data and time points max, don't need a Cray Supercomputer to crunch that sample size. 

The AMP guys are at least one step ahead in that they appear to control the time axis with a machine press which ensures that every stroke is the same duration. That's way beyond where I'm starting, but it's certainly doable; computer-based servo motor control is within reach of anyone who wants it. Whether it's worth it to control stroke duration is something I'll get a better feel for once I get past first base.
Chris

Re: Metered arbor press bullet seating question

Reply #6
If you want to compare curve shapes I think you will find it is critical.

Re: Metered arbor press bullet seating question

Reply #7
Now that I have all the gear in hand, I wanted to dredge this up as it swung in an AMP-lite direction, for good reason.

What AMP appears to have made is a machine which enables them to illustrate the effects of annealing, which makes sense. I'm not looking to do that; I already anneal brass every firing now.

Circling back to any of the gaged arbor presses, K&M, 21st Century etc., what does the indicator gage tell you that this particular seated round belongs in this sort group, and that another seated round belongs in that sort group?

If you don't use the press to group seated rounds, maybe just to gage how consistent your neck tension is, what does the the indicator gage tell you so you know where you are at?

To my way of thinking the gage movement is a fleeting, observable event; are you looking for needle jerkiness, peak force, or what? To be useful, the gage has to tell the operator something, that's what I'm hoping to learn more about.

Thanks.
Chris

Re: Metered arbor press bullet seating question

Reply #8
Chris I think you asked that question in your first post here.

My answer was:
Pressure required to initiate bullet seating (first stage of entry), slope of the seating curve, and peak pressure of that curve.

As I said before, a recorded slope of the curve is not available with current equipment, so you can only try to visualize it. The only measurements of value with current limitations are starting an peak pressure.

Re: Metered arbor press bullet seating question

Reply #9
Thanks Jerry, I think the "slope of the seating curve" is what through me off the trail. Got it now!
Chris