View Full Version : Home made heavy sprue plate?
06-04-2005, 04:25 PM
I was wondering if anyone here has made their own heavy 1/4 in. sprue plate to enance say a Lyman mold? I was wondering about heat treating or not or stress relieving to combat warpage? Probably some type of tool steel would be better than just plain mild? I don't know,thought some one could tell me what works for them.
06-04-2005, 04:29 PM
I have made a few, I used A2 steel because I had some, and I like it, I didnt heat treat them...they turn a nice plum color with use.
there is quite a bit of info on one of the other boards here in a thread about "leaded steel for mold blocks" or such.
06-04-2005, 05:40 PM
There were several articles in the American Rifleman in the 70s about thick sprue plates made from aluminum. Col Harrison found them to work exceptionally well. The articles have been reprinted in the NRAs Cast Bullet book. I made one for my Lyman Polstel mould for my Sharps and it works much better than the original thin steel plate. I haven't seen anything comparing to a thick steel plate but it does have the advantage of not being wetable by molten lead and the aluminum is easier to work with handtools than steel.
06-07-2005, 07:53 AM
The aluminum plate will probably fatigue crack sooner or later. In addition, steel gives a better shearing cut on the sprues. Try some sort of High carbon/ Alloy steel, such as O-1, 5160, 6150, 1074, 1095, or 4140 Prehard. Air hardening tool steel will work, but is more difficult to heat treat, you can do it in oil, but cracking is a possibility. Greg
06-07-2005, 09:54 AM
Honestly, and not to argue, but I can't see why a sprueplate should need to be hardened.
06-07-2005, 12:59 PM
It doesn't really need to be hardened, but it adds to the strength. The hardened plates will take a beating better, and resist deformation. You can use the 4140 Pre hard at 28-32 Rc C. Check out EBay for the prehard 4140.
06-07-2005, 03:03 PM
The plates don't have to be hard. I make mine out of 1/4" stainless that I have to mill flat. My problem is I can't cut the sprue hole with countersinks. I have to chuck the plate in a four jaw chuck and use a lathe bit I made to cut the taper.
The stainless was free so I can't complain. If you use wood to cut the sprues you will never damage the plate or mold.
06-07-2005, 05:51 PM
A steel plate is certainly stronger than aluminum, however, I've cast a bunch of 535gr 458 Postel bullets for my Sharps using an aluminum plate. It still makes a square base with an evenly cut sprueCol Harrison thought the aluminum plates were superior and he was not one to make rash statements. I agree, a steel plate will certainly outlast an aluminum one, but a thick, carefully made, and not abused, aluminum plate is very easy to make with just handtools and it will last for an awful lot of bullets and it never gets smeared with lead. My 2 cents.
06-07-2005, 08:02 PM
Your are right, the plate doesn't need to be hard, just able to hold the sharp corner for shearing the sprue. The steel plates could be made from Hot roll material, and probably not warp in the annealed state. If they were heat treated, you will porobably have to grind them flat. The Aluminum will probably work, but warpinbg might be an issue. I am unsure, but isn't moist thin aluminum, cold formed? You probably would use 6061 or 2024 Alloy, I would check to see how they are formed before using. You could even use mild 1018 steel if you wanted.
I use a large rubber piece to hit the sprue plate, and have no problems. As long as you use a forgiving material, there should not be any damage to the plate. Several custom commercial mold makers tell me that the plates should be hardened for durability. Make sure the countersunk hole has a nice knife edge, so sheraing the sprues is easier. On small bullets it probably does not make a difference, but on a 770 grain bullet with a .250" diameter sprue it helps. Greg
06-07-2005, 10:08 PM
I use the GMW plates. They are, I think, made of hot rolled steel, CNC cut out, then surface ground true on both sides. They have long handles and I only use a gloved hand to open, no hammering. He sells them for $15.00 delivered, or at least that was the price last year (for Lyman).
06-09-2005, 05:48 PM
We've experimented with both 1/4" and 5/16" plates with various diameter sprue holes. No hardening. They worked fine.
A fellow that I once shot with made SS plates and swore by them although I never used one of them as he moved before I could swindle one out of him. He said SS was the only way to go. No sticking or lead build up on the bottom of the plate when you get one too hot.
I have maybe a dozen home made and replacement thick plates and I don't see that they're worth the extra cost./beagle
06-09-2005, 07:02 PM
I have some 416 stainless, that would work, but it machines less easily than O1. 300 Series stainless would not be a good choice, because it is difficult to machine, even though it is not hard. If the stainless is not magnetic, I wouldn't use it, as it is probably 300 series. Greg
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