Author Topic: Mold casting undersize? (Read 748 times)

Will52100 · « **on:** December 22, 2004, 05:13:10 PM »

I recently got a new mold and with straight wheel weights it cast .001-.002 undersize. It's suposed to cast .454, but it nearly cast a .452.

I'm using straight WW and Frankford arsenal grafite spray mold release. Think the mold release could be acounting for the missing thousand or so?

What cast larger, WW or pure lead?

Thanks,

Will

Graybeard · « **Reply #1 on:** December 22, 2004, 07:23:34 PM »

Why would you want it to cast at .454"? Is this the Lee 6 Cavity? If so, have you asked the other guys with them what theirs are dropping? I thought it was to drop at .452".

But if you just gotta have larger you can lap them out. I've got some instructions copied to an MS Word file posted by folks here long ago. I'm sure they're still here but the search feature is not working right now and I do have them copied to a Word file.

Leftoverdj · « **Reply #2 on:** December 22, 2004, 07:56:39 PM »

Yeah, the mould release will reduce the bullet size a thou or two. Lead casts a bit smaller than WW, too. Linotype will cast bigger yet.

Cleaning the release agent out should get you the thou you need.

Lead pot · « **Reply #3 on:** December 22, 2004, 08:21:25 PM »

Will.
You can lap a mould but you must be careful with a aluminium mould if that is what you have, when you lap, for it don't take to much to go to far.
This is how I do it. I drill a hole in base of a cast bullet were the sprue was cut that fell from the mould you want to lap. I use a 1/2" or 9/16" #7 or 8 sheet metal hex head screw and screw it in the base of the bullet. Next I use premium buffing compound, like dico it comes in a stick. I scratch a little off the stick on to a glass plate and mix it with a little cutting oil till it is a smooth past next I roll that bullet in the compound just hard enough so some inpregnates into the lead a little then put that bullet back in the mould and just roll it with your finger a little to settle it in and get the mould coated with the compound re coat the bullet again if you need to and put it back into the mould and close the blocks.
Now you can use a nut driver and spin that bullet in the closed mould till it gets a little loose then use a drill with a driver and spin that bullet in the mould. but you want to take car you don't slip off the base of the screw or you might damage the cavity base edge.
The compound I use is dico E5 emery for cutting and SCR to polish.
Or you can use pumice or rotten stone and oil. I use this for lapping barrels with a lead core. you can get this in paint stores.
Remember if your blocks are aluminium they lap fast. I hope this will help you.
I have used this method for out of round moulds and taking some tool marks out.
Kurt

Will52100 · « **Reply #4 on:** December 23, 2004, 07:55:44 AM »

It's the 6 cavity Graybeard, it's suposed to drop .454 bullets. I'll try cleaning the mold release out and see how it goes. .452-3 works, but .454 get's a little tighter groups. The bullets are used in a Henry rifle.

So far I'm very happy with this mold and design, mainly wondering where the other thousanth or so went.

Lapping would be a last resort and I dought if I'd ever go that rout any way.

Thanks,

Will

Desert Duck · « **Reply #5 on:** January 05, 2005, 03:55:12 PM »

I cast .459 bullets for my 45-70 and find that bullets cast of 100% WW will shrink1-2 thousants over 30 days time. If I mix the Wheel weights 1:1 with pure lead the shrinkage does not occur. I don't know why this happens but I have confirmed the result by measurment several times now. :-)

Sky C. · « **Reply #6 on:** January 07, 2005, 05:06:25 AM »

Will-

1. The spray on mould release agents like the Frankford arsenal will reduce bullet diameter by around .001" in my experience for a .45-70 mould.

2. A method of getting you mould to cast larger that is inexpensive and can be reversed (unlike lapping) and will adjust multiple cavities simultaneously is "Beagling" (the handle of a gent on a couple other CB forums).

The details can be found here:

http://www.castpics.net/RandD/mould_enhancement/mould_enhancement.htm

I have tried this and it works surprisingly well. I use a ladle for casting and have never had a problem with whiskers in the vent lines or finning even when using 2 thicknesses of the tape. Might need to alter how you pour the metal into you mould to keep pressure down a bit but this is a great trick and to my surprise - the bullets I was casting came out as round as without the tape. It is definitely worth trying and like I said - you can take the tape off if it doesn't work to your satisfaction!

Best regards-

Sky C.

Will52100 · « **Reply #7 on:** January 10, 2005, 07:57:40 PM »

Thanks, the tape sullotion sounds interesting, I may give it a try next time I break the melter out and see what happens.