Sprue Plate Hole Size

[chuebner]

Is there any given rule on how big a sprue plate hole can be before it becomes too difficult to cut the sprue? I recently acquired a used Lyman 457132 in excellent shape but the sprue hole is only .125. The good thing is that this one casts slightly large at .459 and beagling for the trapdoor should produce at least .462.

charlie

[Le Loup Solitaire]

There is no actual rule, but a couple of ideas are in vogue. Some folks enlarge the sprue pouring hole with the idea that it will provide more pressure and fill out the bullet better and possibly reduce the occurrence of voids...also give better venting. Another idea is that the smaller hole will provide a smaller sprue to cut and that would give a smoother base and decrease the possibility of tearout. Another idea is to not enlarge the hole and to push it over to the edge of the cavity so there is more smooth base and of course less to cut. After endless playing around with these 3 ways for a while I finally just left the holes at around .125 and concentrated on a few other things like height of pour, diameter of pour stream and watched the quality rather than the clock. If you want to do some informative reading on all these aspects, ideas and experiments, I suggest that you try and obtain a copy of "The Art of Bullet Casting" still available from Wolfe Publications. It is a compendium of many articles written by icons in the casting world over the years. Really good stuff. LLS

[John Boy]

I don't do anything to enlarge the sprue holes on the molds. Only out of the ordinary thing is when the mold is hot, swing the plate away from the mold then melt a dab of paraffin in the hole. Purpose - it allows the sprue puddle to separate from the plate with minimum effort. Paraffin does not burn and leave a residue. I use it also to lube the mold pins instead of using beeswax that burns and leaves a reside on the mold halves

Just keep the ladle spout pressed firmly in the hole and pour counting to five. The head pressure will properly fill the cavity for nice bullets

[crabo]

I use a 09 degree carbide countersink to open up sprue holes quite a bit. You get better fillout and a larger sprue.

Just make sure you flatten out the bottom of the sprueplate before you put it back on, or you will gouge up your blocks.

[chuebner]

My sprue plate hole enlargement experiment worked out quite well. I used a new 60 degree countersink tool with cutting oil and enlarged the hole in stages. Eventually went from .125 to .200. I knocked off the flash with 200 grit wet/dry paper and honing oil ending with 400 grit. I cast up some 457677, 457125 and 457132 boolits using this plate and all filled out very nicely and the sprues cutoff with just a little more resistance than before. I am a happy camper.

charlie

[Iron Mike Golf]

Charlie, do you cut sprues by hand or use a stick to tap the plate?

[chuebner]

Iron Mike,

I use an old Stanley slotted screw driver which has a black plastic handle. Works well. When the mold is up to temp I can cutoff the sprue with a push of my gloved thumb but I generally use the old screw driver.

charlie

[w30wcf]

Based on my experiments with sprue hole diameters, ideally a sprue hole that is 1/3 the bullet diameter is pretty darn close to being the best option.

Too large and you increase the chances of trapping air in the bullet.....

w30wcf

[JIMinPHX]

I occasionally make custom sprue plates for people. Some ask for big holes. Some ask for small holes. Different people claim that different size holes are best. In general, the guys that want big holes are usually using them for big caliber boolits & the guys that want small holes usually want them for .22s. I think that the amount of venting in a mold makes a difference as to what size sprue hole will work best too. When everything is said & done, I generally use standard size sprue holes for everything.