hemis center

[asdercks]

Hi guys, question, how do you find the center of your shell casings where you drill the fuse hole?

[NeighborJ]

A lot of my hemis have a dimple from the mold it was pressed into but otherwise I don't find it to be that criticle. I'll just eyeball it and it's fairly close. The stars hardly ever lay in the hemi with perfect order anyway.

[asdercks]

I hear ya, I always eyeball it as well but I am using shell wraping machine and I want to make sure I place the shells well centered, it seems I am getting slightly different taping patterns from shell to shell and my guess is that those variations are caused because of the shells not being well centered

[NeighborJ]

You can measure with a sewing tape. Or I usually just place various plastic can shells on top to trace concentric circles to follow while pasting, I eyeball those as well. But if you still have issues you can use a compass.

Usually after a few times around I get a little stretched on one side so I just let the tape double over one side until everything straightens out then I continue wrapping as usual. I guess to prevent this you could also use a same size hemi to make a circle around the shell for a good starting line. It's kind of hard to explain without pics.

Edited December 4, 2016 by NeighborJ

[Raceman17]

I hear ya, I always eyeball it as well but I am using shell wraping machine and I want to make sure I place the shells well centered, it seems I am getting slightly different taping patterns from shell to shell and my guess is that those variations are caused because of the shells not being well centered

Once u put the fuse end of the shell into the wrapping machine look down the centerline of the shell clamping mechanism and just eyeball the center of the non fuses hemisphere and adjust that side to make it rotate on the centerline of the shell. It should be centered up at that point. In all reality the fuse location is not critical at that point because you will be adjusting the non fused side to make the shell rotate on the centerline.

Edited December 4, 2016 by Raceman17

[Col]

I knocked up a simple jig out of mdf. Drop the hemi in, rotate the lid so its closed, screw in the screw to make a dent..done. I could omit the marking screw and just drill through but the hole would probably enlarge over time. I mark both hemi`s and only need one with a hole so the screw is better for me

 

For machine pasting, center mark both hemi`s and then draw circles on the hemi`s the same diameter as your machines clamping tubes.holesaws etc. Match the circles to the clamps and you`ll be aligned

Edited December 4, 2016 by Col

[asdercks]

Got it, will do that, thanks raceman

 

Neighboor thanks for your suggestions, you gave me an idea

[asdercks]

Nice jig Coil I really like it

[Col]

thanks mate, its mostly 4mm mdf glued and stapled together. The hole in the bottom plate is for aligning the passfire tube perfectly plumb in the middle of the shell.