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63 Shiloh
05-27-2011, 07:32 AM
I am having problems with my 9.3 4 cav NOE mold dropping boolits with a cantered base.

Only on the GC cavities, the boolit base has a slope on one side of the base, these slopes are on the same side of the mold.

I have tried adjusting the sprue plate tension in and out with no joy.

I believe the sprue holes are cutting this slope on the base of the boolits. I am going to sand the sprue plate on a pane of glass with some fine wet and dry, hoping this will true up the sprue holes.
Hey Fellers,


Any tips or possible ideas of what is going on?


Mike

btroj
05-27-2011, 07:41 AM
How severe is the slope?
If the GC fits properly, meaning squarely, then I would see how they shoot. May not be a big enough problem to affect the accuracy. This is a situation where I would let the gun decide if it is a problem or not.

Calamity Jake
05-27-2011, 08:28 AM
I am having problems with my 9.3 4 cav NOE mold dropping boolits with a cantered base.

Only on the GC cavities, the boolit base has a slope on one side of the base, these slopes are on the same side of the mold.

I have tried adjusting the sprue plate tension in and out with no joy.

I believe the sprue holes are cutting this slope on the base of the boolits. I am going to sand the sprue plate on a pane of glass with some fine wet and dry, hoping this will true up the sprue holes.
Hey Fellers,


Any tips or possible ideas of what is going on?


Mike

If the slope is in the CG'ed cavitys only then I would think it happened when thoes cavities were cut and no amount of sanding on your part is going to fix it.

Take some pics of boolit and cavity and email them to NOE, I think if the cavitys were cut in an undetected setup problem then he will fix it.

44man
05-27-2011, 08:33 AM
Sanding anything on glass will take a plate out of flat very fast. Most sanding or lapping action will take place at the edges no matter how much care you use. Nice way to build a rocker! [smilie=l:
That mold sounds like the cavities were cut out of line with the mold top.
Since the sprue plate should ONLY cut the sprue, the edges of a boolit should not be touched or cut unless you are cutting almost molten lead and shifting the boolit in the cavity. You should never cut lead before it sets up.
If the cutter is dull, sharpen from the TOP and only de-burr with a swipe at the bottom. A dull cutter can force a boolit sideways if too soft yet.
Some cut molten lead with a gloved hand. Like cutting Jello!

steg
05-27-2011, 01:03 PM
+1 with 44man, it's impossible to keep an even pressure on something like that. its the way the larger telescope lenses are ground, counting on this uneven pressure......................steg

Canuck Bob
05-28-2011, 07:27 AM
Regarding lapping, a lap plate is best made from a very flat material softer than the piece being lapped. In a machine shop tool steel is lapped on a cast iron plate. The abrasives embeds itself in the plate like sand paper its locked.

With glass the abrasive rolls around and this moving causes problems at the edges as noted. I lap using wet dry paper on the glass plate. Some auto parts outfits stock very fine grits that are not very aggressive and leave a nice finish, + 1000 grit. But lapping is a polishing procedure for flatness. If your trying to mill it can be real hit or miss. Besides it sounds like you could mess up the good bases with a little error in lapping if I understand correctly.

geargnasher
05-28-2011, 01:01 PM
Cut the sprues sooner, before they get rock-hard, just at the instant that they're solid enough to not smear, when you can still do it by hand without hitting the sprue plate with a mallet. Sounds to me like you're cutting the sprues after they've set, and with long sprue plates that multi-cavity moulds have it's easy for the plate to "skip" over the top of the base, leaving a teat or lump on the base that can be off-center.

The other possibility that comes to mind is that the mould blocks are out of alignment on the GC cavity end, this is easily checked with a straightedge and a light with the mould blocks closed and the sprue plate open, see if one block is lower than the other. If so, you have an alignment pin or handle issue.

Gear

63 Shiloh
05-29-2011, 05:41 AM
Problem solved!

De burred as mentioned and ran the plate over my diamond block a few times. Used bulldog clips to hold the 800 grit wet and dry with some oil, carefully did the top of the blocks.

Checked everything out for square, spot on, although I do have a very slight rounded edge on the end of the blocks.

Casted up 200 boolits, all nice with flat bases.

Cheers Fellers,

Mike

Canuck Bob
05-29-2011, 07:28 PM
Congrats!!! Don't you like it when a plan actually comes together! Your a bonafide mould mechanic now.