Sprue Plate holes.

[redhawk0]

I have a variety of mold brands and I love the Lyman sprue plate above all others. Its thicker and it has a slightly larger hole which is easier to hit when I trickle pour my bullets. I don't generally pressure cast from the pot nipple..I fill from the stream of lead (that's what I meant by trickle pour...someone please provide the correct term for this method....thanx) I end up with a nice sprue puddle on the top for limiting the amount shrink as the lead in the boolit cools.

Now my problem....
I have a RCBS 44-250KT mold that has a much thinner sprue plate and smaller diameter fill holes. I have trouble hitting the hole and sometimes get poor fill-out if I miss and "glaze" over the hole with the lead stream before it fills the cavity.

What is the easiest way to expand the hole? With a drill? What angle are the sprue holes...and does that really matter if it is matched exactly? I fully expect that I'll need to lap the underside of the plate once the hole is enlarged and that doesn't sound like it should be a problem. I'm just not ready to damage a sprue plate by drilling it incorrectly...so a little advice would be appreciated.

redhawk

[Dan Cash]

I have opened sprue holes with a 45 degree counter sink then lapped the bottom of the plate on some 400 grit wet or dry sand paper. I doubt that there is a proper hole size or chamfer angle. Good luck.

[country gent]

Opening up with a drill you end up with a wide straight "land" on the bottom edge of the sprue hole that may tear and cot cut the sprue clean. This straight area may make release of the sprue harder also. On the few Ive opened up Ive used a 90* countersink at very low speed and cut to the depth to enlarge the hole. The counter sink leaves a sharp edge to cut the sprue cleanly, Enlarges the whole sprue hole in size from top to bottom. This angled hole makes sprue release easier also.
Several things to keep in mind. Run the countersink slow rpms this helps cut down on chatter, I have set up in the drill press and put a rod in the hole of the chuck and turned by hand with pressure on the spindle with the other hand. This will give a very clean cut. I clamp the plate down on a block of wood on locations so both hands are free. This makes turning by hand much easier. If you know the size hole you want then drill a slightly smaller hole in the block of wood first and set the plate over it, when you see wood cut your there. You can drill the hole thru the plate into the wood but sometimes seeing the flat is harder. Use a sharp countersink and plenty of cutting oil, for this the old black oil is very good. Last is you will raise a burr on both surfaces so be sure and stone these off top and bottom. A wood dowel can be made with a 90* end and fine lapping compound used to finish the surface if desired, this can be used to remove any chatter or cut lines left. Valve grinding compound too remove the rough surface then comet toothpaste or flitz to finish. When finished the new hole should be smooth and show no rough spots or chatter marks.

[country gent]

If your going thru the trouble of opening the hole making a new thicker plate is hard with a hacksaw and a few files. I have some moulds that Ive made 1/4" plates for. most are 3/16" thick some thinner still. A new late 1/4" thick with the desired hole size and vented to the front edge may be just the ticket. The 1/4" thickness gives a thicker bigger sprue. Pick up a piece of gage stock 1/4" thick this is ground flat already. Clamp the existing sprue plate on top and cut around outside edge with a hacksaw leaving a little stock to clean up the saw cut with a fine file. Spot the holes thru the old plate and drill to size,Pilot drill.010-.015 small and then use the correct size drill as a reamer to finish holes. Cut the sprue holes as mentioned in above post. Lapp sprue hole and polish new plate on a hard flat surface start with 320 grit with light oil and work to 800 grit and light oil. Break the sharp edges with a nice chamfer.

[WALLNUTT]

Thicker plates are available from RCBS at no charge. The holes may be the same size.

[redhawk0]

Thanx guys...I knew if I asked you guys would come up with some good info. It truly is appreciated. I just might contact RCBS and see what they might have for this old mold. I purchased it second hand over on the S&S forum and I believe the mold is not current production...but if the spacing of the holes are correct after mounting the pivot...who cares?...actually...even if they are slightly offset from center it won't really matter...a flat bottom is a flat bottom as far as I'm concerned.

redhawk

[hunter74]

I've used a drill bit from the top and just drilled the hole bigger. The burres on the bottom can easily be removed with a flat file and a dremmel and some fine paper. I've used a dremmel and some grinding compound and deburr and polish to a morror finish. It's important that the underside of the sprue plate is free from burres. You don't want to scratch the top of your mould.

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[redhawk0]

I sent a note off to RCBS...this plate is only 0.128" thick with holes that are 0.12" in diameter. Their web page lists current production 44-250-K (without the T) as having a 3/16" thick sprue plate. I'll have to see what they say. A hole in the 0.18" range sure would be nice.

I'll get back to this thread once I hear from them...then I'll decide which direction I want to go with replacement/modification of the current plate.

again...thanx for the insight.

redhawk

[toallmy]

I can't really say how to properly open up the holes in a sprue plate besides taking a little bit off of the bottom of the plate . But I can tell you to spend a minute or two thinking about a drill to do it , I ruined a saeco 4 cavity sprue plate with a drill bit and a replacement was on back order for a long time . A kind member hear helped get my plate fixed up good enough to cast with temporarily .

[Grmps]

Get a better pair of glasses

I touch up a lot of my sprue plates to get a better cut off, I use a countersink similar to the existing angle and hone the bottom smooth.

[lightman]

I have opened sprue holes with a 45 degree counter sink then lapped the bottom of the plate on some 400 grit wet or dry sand paper. I doubt that there is a proper hole size or chamfer angle. Good luck.

I've done this before too! Its easier if you have a drill press. I would probably call RCBS first and see if they will send you another one. My newer molds have a thicker plate than the older ones.

[redhawk0]

Get a better pair of glasses

Yeah...that too would help....but what do I do about the old age shaky hands. Actually, I'm not so bad in that regard yet....but I have noticed I'm not as rock steady as I once was. In this regard...I have an idea. What I've notices is that my Lyman mold is a HP design so the HPer hangs off the bottom and I can rest the knob on the bottom of my pour pot tray. This gives me a steadier support for my pour. I got to thinking that I might make a small aluminum block that I can sit on the tray floor then rest standard molds on it for support. The small block would act like the HPer knob for stability.

I'll see what RCBS says about the sprue plate. I've dealt with them before and they've always been good to me.

redhawk

[CJR]

Rehawk0

In my view, if your RCBS 44-250K mould has sprue holes of 0.12"D they are too small. Small sprue holes "throttle" the hot lead flowing into the mould and in so doing significantly cools the lead entering the cavities (i.e. lead fluidity is reduced) and improper cavity fill-out results. The sprue hole needs to be large enough to allow rapid molten-lead entry into the mould cavity, with NO PRE-COOLING of the hot lead alloy, so as to give proper fill-out of the cavities. Typical "Band-aid Fixes" for undersized sprue holes is to increase the lead alloy temperature to increase the lead fluidity entering the cavities. Not a good practice. Likewise, undersized sprue holes tend to promote "macro-segregation" (i.e. a large density variation WITHIN the casting). This results because multi-constituent (Pb-Sb-Sn) alloys (like lead) have a temperature range of melting & solidification points. This phenomena/chronic problem, in castings, has been known since the year 1540. When a CB has a large density variation WITHIN ITSELF, it will not be as accurate as possible. We're not talking about a weight variation among many CB, we're talking about a significant density variation within A SINGLE CB.

The NRA, years ago, did a study on how sprue hole sizes affect CB quality. See, NRA Cast Bullet Manual-Supplement No.1, pg. 14, free on CastPics. The NRA found that sprue hole diameters should be about half the size of the CB diameter. For a 30 cal. CB, the sprue hole diameter should be 0.150"D. I have corrected all my sprue hole diameters, on my moulds, according to this NRA spec. The sprue holes, on my Lyman 429421 Keith four-cavity mould, are at 0.218"D and cast excellent quality CBs which are accurate at long range. Hope this helps.

Best regards,

CJR

[redhawk0]

@CJR...great information. I've never heard this before but it truly makes sense. I'll definitely check out the NRA article you mentioned. Sounds like all my molds may need to have some "touch-ups". Until now I've always just trusted the mold makers to know what they were doing. It seems evident after working with this mold that they really don't.

much appreciated.

[EDIT] - Looks like the NRA files aren't on castpics.net any more. I select the article but the page comes up blank. Even tried multiple browsers. Does anyone have it that they can share over to me.

redhawk

[CJR]

Redhawk,

Here you go. See if you can read the file.

Best regards,
CJR

NRASprueHoleArt-2.jpg (68.7 KB)

[hunter74]

Very interesting article! I have struggled with good fillout with my Magma 240 Swc moulds when running my Bullet Master. It got better when I turned the heat up by 30F. Maybe I'll try to open up my sprue plates.

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[redhawk0]

The image resolution gets pretty bad when I make it a readable size...but I can read it with difficulty. Its a very interesting article. It also sounds like I should investigate my bottom pour spout size as well. I'm not sure what modification can be done to a Lee pot though.

I think my next pot will be a dipping pot and just use multiple ladles for small vs. large diameter boolits. For right now....my setup works on all molds with the exception of the one mentioned in this thread. I cast .224" - .458" and .490" RB, but I'd separate my small vs. large at the .357 / .401 line. I currently have quite a few .401, .429, .458 molds and just this one 44-250-KT is problematic. But I can see how sprucing up my sprues for the future might make casting better on these larger molds.

Again...CJR....much appreciated for taking the time to post the article. BTW...I found all the NRA articles on castpics to be missing...not sure why.

redhawk

[CJR]

Hunter74,

If you have multi-cavity moulds with non-connected individual sprue holes, machining a trough, that connects the sprue holes, will also speed up production and improve quality. The NRA also did a study on that mod as well.

I note you're from Norway. I recently watched a video entitled, "The Heavy Water War". An outstanding WWII true story filmed in Norway, I assume on The Plateau where most Norwegians hunt.

Best regards,

CJR

[Grmps]

I currently use a piece of 2x4 with the top and 2 sides wrapped with thin steel, I add thin pieces of plywood under the block to get each mold to my desired height.

I've seen bottom pour pots with a "track/rails" the mold slides in. This would get your molds centered side-to-side. You could put a moveable stop at the end to center the sprue hole nearest you then mark the track for the sprue hole farthest away.

I've thought of doing this and possibly filing notches along the bottom corner of my longer molds (lined up with the sprue holes) with a matching "bump/detent" (lined up with the spout) in the track so I could feel when each cavity of the mold is centered under the spout.

As long as you keep the spout clean and have a straight flow, this should take all the guesswork out of lining up the holes.

NOE makes a guide that might help

https://www.youtube.com/watch?v=__XfjxHZB1w

http://noebulletmolds.com/NV/product...ue5m6v32hgeb87

my 2¢ worth

[CJR]

Redhawk,

I don't use electric lead melting pots. My setup is a turkey propane burner with a portable doughnut shaped plate 22"-24"OD x 3/8"-1/2" thick w/ center hole cutout of about 6"ID, set on the burner, so the flame can heat the pot while the rest of the plate heats up other moulds. The trick is to adjust the height so you can comfortably REST a heavy mould on the edge of the large lead pot so that most of the mould is over the liquid lead. This gives a steady mould to pour into and reduces unsupported holding time of a heavy mould. You don't tire so quickly using a heavy mould. Likewise a trough machined into the sprue plate, connecting the sprue holes. speeds up the casting process. Everything we can do, i.e. larger sprue holes, sprue plate trough, a steady mould, etc., to keep the liquid lead flowing as fast as possible into the cavities (without throttle precooling) will produce good CB quality. Likewise, we get higher CB production levels at lower lead pot temperatures.

Best regards,

CJR