Crazy mold

[44man]

I have one of my home made molds driving me nuts. It makes perfect boolits and then all of a sudden I get flash on the base. I can see light under the sprue plate angled up from the hold down bolt. I have tried lapping the mold top and bottom of the plate but that makes it worse. No way to lap anything and get it flat. The edges always wear more then the center. I finally milled the bottom of the plate again just enough to clean it up. It is 3/16" stainless. It worked for a while and started leaving flash again.
I then milled about .001" off the top of the mold, no luck! I tried peening the top of the bolt hole on the plate to close it so it hugs the bolt and it helped a little.
I gave up and heated the plate red hot and let it cool.
Now it is laying flat and is rubbing the whole top of the mold. I have to cast again to see if it stays flat.
I have cast a thousand boolits with this mold without a problem, it just cropped up all of a sudden. No, I didn't do anything different.
Using a straight edge on the mold top and bottom of the plate shows no warp that I can see.
I keep the bolt lubed and can't see any wear from the plate on top of the mold. This is the only mold doing this.
If this keeps up I am going to replace the plate stop pin with a screw so the plate locks down under the screw head.
Some higher power wants to make me fully bald!

[Red River Rick]

44man:

Like I mentioned earlier:


Your choice of material may not be the best. The 300 series stainless in natorious for galling and will probably distort and warp after useage.

If your wanting to use stainless steel for a spru cutter plate, the 400 series (416) would be a better choice. Due to the fact that 416 is heat treat-able, it tends to be a bit more stable.

Boolit casting temperatures are pretty close to draw back temps so any stresses in the 300 series stainless may be relieved, causing your problem.

RRR

[montana_charlie]

No way to lap anything and get it flat. The edges always wear more then the center.
When you lap, do you use a figure-eight motion? This ensures that each portion of the piece travels the same distance over the abrasive. Beats the heck out of back-and-forth, and circles...
CM

[floodgate]

44 Man:

Looks like a clear case of the sprue-plate suddenly up and warping. The idea of a screw in place of the stop pin is an excellent one; Modern-Bond started doing this in the early 1920's, and Hensley & Gibbs adopted the idea some years later (M-B and H&G DC sprue-plates will actually often interchange, though the screw threads are different), and probably other mould makers do so too. In using the Lyman moulds, I find that if you close the sprue-plate too hard, it will raise a burr at the stop-pin notch; I always de-burr the lower edge of their sprue-plates before using them, and cut a substantial chamfer at the bottom of the stop-pin notch, and remember to close the plate gently (I hook it around with the rawhide mallet that lives in my right hand while casting, at least with my bottom-pour 10-lb. pre-Lyman SAECO - which is at 45+ years and counting).

floodgate

[44man]

Rick, this is T 304L HT picked out of a dumpster. I have had no problems at all with about 15 others. I get no galling and they run very smooth on the blocks, no scratches on the amuminum at all. There just must have been some stress in this one piece. Seems as if getting it red hot flattened it out.
Floodgate, I always round off the edges on every plate and polish them. I treat them very gently and never close hard or slam the plate shut. I am very easy on molds.
CM, I always use a figure eight but it doesn't help. The edges will always come out a tad thinner and is enough to rock a sprue plate. Even with a perfect flat edge on the plate, it can't really be seen by eye, but it will be there.

[44man]

I made 250 boolits with the mold today and the plate worked perfectly. All clean bases.