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BP granulated size


Jordan123

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Hi guys,

 

I will know what the screen mesh i must buy for good BP granulated ?

I use BP for 3inch up to 5inch cylindrical and spherical shell.

 

Because, now, i have buy a BP puck press and before i have a plastic screen, but now i must buy a "real" screen, please what size i must buy ?

I have already buy 4mesh metalic screen.

 

Thank you !

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I think 4FA is used often for 3" breaks and probably work for lift too. I have lifted baseballs in 3" mortar with both 2FA and 4FA. 2FA I would use for lift on 3" to 5" shells but I'll defer opinion to those who have worked with those sizes. Below is a chart with mesh sizes as they relate to BP grade.

post-14334-0-05172000-1370384625_thumb.jpg

Edited by Bobosan
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I use a slightly modified set of cutoffs. I use a range that spans 2FA and 3FA (-4+16) for lifting and breaking most shells. When I need something stronger I use a modified 4FA (-16+30). With these cutoffs, I get minimal fine material, and everything seems to work pretty well. I can always screen the real 2FA or 4FA if I need it.

 

I agree with Bobosan here that you will probably find that you need both 2FA and 4FA to successfully make those shells you're interested in. This means that you'll need a 12 and 20 mesh screen. While you're at it, you may want to consider getting something in the 30 to 40 mesh range to use for mixing compositions.

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You don't need to press and corn BP to make BP for lift and break. A press is nice to have but not a necessity when starting out. There are people that use BP coated rice hulls for both lift and break. Or you can wet granulate BP and screen out a useable size. Good stainless screens can be expensive. You can get different size hardware cloth and window screen at a hardware store that will work fairly well for certain tasks. You could probably get away with just that or at least decrease the sizes you need in expensive stainless.

 

Also, it is probably better to make bigger screens than you think you need. 12" x 12" (a square foot) is pretty small. You probably will rather have something like 12" x 24" or even bigger. I would research what pros use.

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With a small mill I used 4" (100mm) squares of mesh melted into the bottom of stacking sandwich boxes. (from mcconme on ebay.co.uk)

with a larger mill 12" sieves from Cooperman435.co.uk again welded into a larger food storage container with a soldering iron!

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In the chart above, I would call -8+12 = 2FA. You're just sifting the granules to a more uniform size with an 8 mesh screen and removing the large 4 mesh chunks.
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You can use whatever works. 2FA is one of the most common grades though, so much experience and advice is in relation to having that particular grade.
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The important thing with powder is repeatability. You need to have confidence that the powder you tested with will be the same as the powder you use next time.

 

Once you have perfected the mixing and milling then the corning/ricing must be consistent. Most users will approximate to 2Fa, 4Fa and maybe 7Fa and use meal for fusing.

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