Sprue Pivot question?

[Greg5278]

I am making another run of Blank Mold blocks, and wanted to see what size Hardware you prefer. I usually use Shoulder screws for the Sprue plate pivot, and stop pin. I have been using 3/8" diameter shoulder srews on my oversize molds with 5/16 threads. What thread size would you think is appropriate for most molds 10-32, 1/4-20? What Shoulder size would you use?

My other question is whether people prefer the wave washer arrnagement, or a bronze washer for holding the spue plate to the pivot? I have seem them both ways. On molds with larger hard to cut sprues, I have eliminated the wave washers. On smaller molds the washers seem to be okay, but cut sloppy with some alloys.

I appreciate any comment you have on the design of these molds. They will be 1.750 by 1.750" by 1.750". They should allow 2 cavities for up to .50 cal bullets.

Thanks,
Greg

[Buckshot]

I am making another run of Blank Mold blocks, and wanted to see what size Hardware you prefer. I usually use Shoulder screws for the Sprue plate pivot, and stop pin. I have been using 3/8" diameter shoulder srews on my oversize molds with 5/16 threads. What thread size would you think is appropriate for most molds 10-32, 1/4-20? What Shoulder size would you use?

My other question is whether people prefer the wave washer arrnagement, or a bronze washer for holding the spue plate to the pivot? I have seem them both ways. On molds with larger hard to cut sprues, I have eliminated the wave washers. On smaller molds the washers seem to be okay, but cut sloppy with some alloys.

I appreciate any comment you have on the design of these molds. They will be 1.750 by 1.750" by 1.750". They should allow 2 cavities for up to .50 cal bullets.

Thanks,
Greg

..........For the mould SP pivit bolt a 1/4 shoulder should suffice, although 5/16" to 3/8" would be better if the cavity location would allow them, with an appropriately larger head. If the person operating the mould is swinging the SP properly to use or not use a pressure washer of some sort is kind of irrelevant. I use a flat brass washer against the mould block and a wave washer atop it, held by the screwhead.

.................Buckshot

[Willbird]

I played around a bit with a lyman mold, I tried to make a double sprue plate with one on the top and bottom of the block. That taught me that things grow when they warm up. What kind of pivot you use will have something to do with what metal you make the sprue plate out of.

If your using an aluminum sprue plate you will need some means of accommodating the fact that it expands at a different ratio than the shoulder bolt.

Even with a steel sprue plate the rig I made would benefit from SOMETHING like a wave washer to allow some leeway there.

Magma uses a coil spring and a longer bolt(the spring is actually puling the bolt from the bottom side of the mold block), but that interferes with the handles. This keeps the spring away from the heat too.

here is magma's drawing of how they do it

http://www.magmaengr.com/images/drawings/handcast.gif

Bill

[Greg5278]

Thanks Buckshot, I changed the bolt to a .250" diameter shoulder screw with a 10-24 thread. That should be fine for most applications. I will use the same .3125" shoulder length to allow for a wave washer, or a bronze washer for heavier cutting. As a note, a large sprue of .220" in pure lead or Lead/Tin alloy is a real PITA to cut, compared to shearing several smalle rsprues all at once.

I will probably have the Sprue plates waterjet cut from the 4140 prehardened material. I can always use the prehard 5160 steel too, it is very tough. the only problem is the tendency to throw a burr, when drilled. A little lapping compound to clean up, and it should last forever. I have been using O1 sttel, hardened to 58 Rockwell C, and they have lasted so far, and are still sharp. I wonder if using a differnet angle Counstersink would help. Perhaps swith from an 82 degree one to a 135 Degree one. The force required to shear the sprue should be less. The hardened steel will resist deformation much better than some of the **** production plates out there.
Greg

[Willbird]

Have you checked hardness after using the mold awile ?? I ask because the tool steel ones I have made took on a color after use that would indicate they had been tempered by use enough that they would not be 58 rockwell if they had started out that hardness.

Bill

[Buckshot]

Have you checked hardness after using the mold awile ?? I ask because the tool steel ones I have made took on a color after use that would indicate they had been tempered by use enough that they would not be 58 rockwell if they had started out that hardness.

Bill

............I'd think that that might be an issue with alloy temps of 600 to maybe 900 degrees and then the heating cooling cycles? At least SOME amount of ultimate hardening would be lost, but enough to make it not worthwhile? Maybe there is a market for some 8% Colbalt HSS sprueplates? :-)

................Buckshot

[shotman]

ok I will do the dummy side since I dont make them just use them. Most of the problems is the user. You could use a 1/2 carbide plate and a 1in bolt and some guys could destroy the mold. Buckshot makes a very good set up and works good . I dont use a 3lb hammer to hit plate with. The best I have found is a 12in piece of hickory hammmer handle. It dont mark the mold and dont put dings in any thing. I aways hit at a downward stroke and that tends to keep plate tight on the cut. Lube its the other factor.. Just my 02 cents

[Cap'n Morgan]

I use an ordinary 6mm socket cap screw, locked with a 4mm socket set screw. The sprue plates are made from 1/4" grounded plate - no washers as I prefer the sprue plate to swing freely. I also use a 6mm threaded stop pin, symmetrically to the hinge bolt. That way you can change the mold to a left hand configuration, just by adding a new sprue plate.

[Willbird]

............I'd think that that might be an issue with alloy temps of 600 to maybe 900 degrees and then the heating cooling cycles? At least SOME amount of ultimate hardening would be lost, but enough to make it not worthwhile? Maybe there is a market for some 8% Colbalt HSS sprueplates? :-)

................Buckshot

I'm sure you have tempered steel just as I have BS. but maybe the color that builds up over time does not indicate the same temperature as if we heat a polished steel part the FIRST time when we temper it??

O1 tempers to 58-60 rockwell at 500 degrees, clear up to 800 degrees will draw it to 48-50. I have made several from O1 AND A2 and just left them soft and they work great.