311291 shortening redux

[gnoahhh]

Yesterday I milled the top off of a 311291 SC mold, down to the lower drive band. I then lapped the fresh surface on diamond stones, and while at it lapped the bottom of the sprue plate dead flat also. (It's amazing how uneven those things are even when they appear flat.) The new surfaces are so flat and polished that one can almost wring them together like Jo Blocks. The new edge between the mold cavity and the mold top is clean, sharp, and square. Now for the problem: When casting the "new" bullets (which come out at 155gr. now, WW+tin) I can't for the life of me get a nice sharp square base. I did the usual tricks including running the alloy temp up in stages 'til I was darn near 900º and cast about 100 bullets which means the mold was surely hot enough. Don't get me wrong, the bullets aren't bad, they're sharply defined otherwise, but the bases are oh-so-slightly radiused. They may well shoot ok as-is, but they do bother me.

Any thoughts? Did I do too good of a job when flattening/polishing both the mold and the plate thus not allowing a venting action to take place at the bottom of the bullet, creating the radiused corners?

[462]

I think your last question is also your answer.

[Ben]

gnoahhh

You question in your OP was :
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Any thoughts? Did I do too good of a job when flattening/polishing both the mold and the plate thus not allowing a venting action to take place at the bottom of the bullet, creating the radiused corners?

______________________________

462 has it nailed .

Look at these photos :

I pay VERY close attention to all my plain base molds to insure that I'm getting as near perfect base fill out as possible. I've experienced the very thing that you describe. Doesn't matter how hot the mold or alloy is, you still can't get good bullet base fill out. BUT..............there is an answer.....and it works very well. Here is how it is done. Takes about 2 - 3 minutes to do the work required.

By the way, if you choose to use this technique to resolve your problem of poor venting at the base area of you mold , when the mold blocks are fully closed and you've done your work with the Swiss fill the line that you've created for air to vent off shouldn't be much larger ( if any ) than one of the vent lines on the mold.

http://img.photobucket.com/albums/v494/haysb/Blocks%20vent%20line/002.jpg

http://img.photobucket.com/albums/v494/haysb/Blocks%20vent%20line/005.jpg

http://img.photobucket.com/albums/v494/haysb/Blocks%20vent%20line/007.jpg

[gnoahhh]

Thank you very much! I shall do as you prescribe.

[Ben]

Go slow.....cast a few.....make a few strokes with the fine cut file ( be careful not to damage the cavity of the mold ) , cast some more....etc. etc.

As soon as you're getting good base fill out without finning ....STOP ! !

Ben

[Catshooter]

Would bet large money that's the problem. After all, you did say you could almost wring the sprue plate and the top of the blocks together. That means no air entrapment. Good luck.


Cat

[Ervin]

For swiss files and really good ingot moulds go to 'jewelry tolls'. Really better prices.
Ervin

[cbrick]

Cutting the edge should work, seems like it would be very easy to go just a little too far too quick or nick the edge of the cavity with a file. I think I would simply loosen the sprue plate just a bit, let it swing freely and see if that doesn't cure the problem first. Could also try something like a wet stone that should remove metal a little more slowly. I have used stones on molds before, never used a file on one.

What you did to the top of the mold and bottom of the prue plate sounds great, also sounds like too much of a good thing ain't a good thing.

Rick

[Ben]

I've used this particular file that you see in the photos above many times. You've just got to remember that you're looking for a parting line on top of the blocks about like the thickness of a vent line. And yes, you MUST go slow with the process.

[Bret4207]

Just to make it sink in- A VERY LITTLE FILING IS NEEDED.

[gnoahhh]

Well last night I re-"polished" the sprue plate with a coarse oil stone. I feel I got the same striations as I would have gotten with a fine Swiss file (which was standing by just in case). I then cast a few, with somewhat better results. I then used the same stone on top of the mold blocks. Voilá! Perfect bases. Amazing how that little bit of venting made a difference.

It did kind of break my heart to wreck that perfect surface I had achieved! (But I'd rather have perfect bullets!) I have a large selection of Swiss files (I use them often in my work) and was prepared to use a fresh one on this. I had the bright idea that dragging the surface across a coarse oil stone, once in each of the 4 directions, might give slightly more uniform results with more omni-directional striations, uniformly across the entire surface. I think the file would have done just as well though, and am almost tempted to experiment on another mold just to find out.

Thanks again fellas. Just goes to show how much knowledge is here on this site, and how much more a 40 year veteran of casting has yet to learn!!

[cbrick]

Thanks again fellas. Just goes to show how much knowledge is here on this site, and how much more a 40 year veteran of casting has yet to learn!!

Another understatement.

I've been casting for 30+ years. In the first 25 years I did improve and learn a lot. Five years ago I joined CastBoolits, I have learned more in the last five years than I did in the first 25.

Rick

[462]

Good news that the mould is working as it should, and I can certainly understand your broken heart.

[MikeS]

Ben:

Rather than filing the mould blocks, would the same effect happen if you filed the sprue plate instead? A replacement sprue plate for a lyman single or double cavity mould is only $8.00 or so at Midway, so if it got screwed up, it's easy to replace. If you screw up the mould blocks you're done, but screw up a sprue plate, and it's fairly easy to replace.

[Catshooter]

MikeS makes a good point.

Gunsmith rule #1: Always file on the cheapest part.


Cat

[Ben]

If the mold blocks can't vent " that last little vestige " of air to insure a good consistent base fill out, I'm not certain if I see exactly how replacing the current sprue plate with a 2nd one will allow the mold to vent ? You might gain a slight advantage by loosening the sprue plate and hoping that the air can vent out with the loose sprue plate.

Very few of my molds don't have this technique used on them.

I think Veral Smith describes this process in his book also.

I'm sold on the technique. The " catch " to it is just how easy it is to over do it and for all practical purposes ruin the mold. I've probably done 30 - 40 molds (a combination of single cav., 2 cav., 3 and 4 cav. and 6 cav. Lee molds ) using the technique you see illustrated in the post above ( aluminum, brass, and iron molds ) , I've yet to ruin a mold.

By using the technique properly, I have taken stubborn molds that didn't want to cast a decent plain base bullet with good base fill out with anyone's alloy, at any temp. and with any casting technique, be it bottom pour or ladle casting and transformed them into molds that will cast well with good base fill out near 99% of the time.

It is just amazing what a very few light strokes with a stone or a fine cut Swiss file on the tops of the blocks will do for venting and good base fill out.

I do want to confess, if I may, that the 357446 HP that you see in the photos above probably has a little more metal taken off the tops of the blocks than I normally would take off.

That photo shows great magnification, however if you were looking at this mold with your un-aided eye , it would look like a very small amount of metal removed. However, it cast perfectly and has no " finning ".

[MikeS]

Ben:

I'm not saying to just replace the sprue plate for the heck of it, I'm saying to file the sprue plate as you did the mould blocks. Then IF you do too much and screw it up you only have to replace the sprue plate, not the whole mould.

[Ben]

This filing of the sprue plate.....Is this to flatten it more , Is it to roughen it up more and create a mechanism for air to vent ? ? ? Not certain if I understand what the goal is ?

Filing on a sprue plate to allow a mold to vent air is a new one on me.

[Ben]

I bought a 38 / 357 , SAECO , double cav. # 053 , 148 gr. w/c mold new in the box.
It arrived today. Guess what ? ? ?

The base didn't want to fill out . I cast about 50 bullets with the mold
perfectly clean......NO GO ! !

So.....I gave it my standard treatment that I outlined above.
( Look close and you can see the " air vent line " on the tops of the blocks. )

After the work, 100% base fill out just like you see in the photos below :

http://img.photobucket.com/albums/v494/haysb/006.jpg

http://img.photobucket.com/albums/v494/haysb/012.jpg

[Doby45]

I gotta get me a swiss file those bases are AWESOME..

[Ben]

Doby45 :

I KNOW that you KNOW........but just remember, file a tiny bit, go back to the pot and cast a few if they aren't filled well and you know that the mold and alloy are the correct temp, go back to the bench with your Swiss file and work some more - - - file a tiny bit, go back and cast, etc. , etc.

Just don't over do it. After, you've been successful with 4 or 5 molds, you can do it in your sleep.

Thanks,

Ben

[Doby45]

Ben, between you and Rick, you two cast some of the purtyest boolits EVER!! And it is because of all these little tidbits you guys have been collecting. Lots of people can make boolits "pretty" but I would put your bases on yours up against anyones. Kudos. :)

[Longwood]

Ben:

I'm not saying to just replace the sprue plate for the heck of it, I'm saying to file the sprue plate as you did the mould blocks. Then IF you do too much and screw it up you only have to replace the sprue plate, not the whole mould.
Please explain.
How would you file a vent line in a sprue plate?
Maybe scribe some lines?
It is a tiny bit of air so roughing up the plate surface with a course stone or emery cloth would probably let enough air escape. I would smooth the plate after scratching it though.
Of course that would involve a lot of work.
It looks like the small bevel he filed at the top mating edge of the blocks works just fine and is so simple to do. I would have no qualms about venting a mold that way.

[cbrick]

I gotta get me a swiss file those bases are AWESOME.

I have done this to several molds but I still recommend a wet stone (can be used dry for this) over a file. Maybe that's just me but the stone will remove metal much slower than a file and for me that's probably a good thing. Very little chamfer is needed, almost if you can see it its too much, too much and you get fins.

Rick

[Ben]

Rick

too much and you get fins.
___

Hence, the reason I've stressed a " bazillion " times to GO SLOW ! !
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Doby45

Thanks for those kind words.

Ben

[cbrick]

Hence, the reason I've stressed a " bazillion " times to GO SLOW ! ! Ben

Yep, I was agreeing with you. And for the same reason I use a stone, it takes off very little at a time and for me that's a good thing.

Rick

[Ben]

I've never tried a stone, I know other people use them ( like yourself ) with good success.

For me, It is easier to put my mold halves in a padded vise so that they are totally immovable, then I can make gentle strokes with the file( with both of my hands on the file to have absolute control on the angle of the cut.

Works for me, for someone else , a slightly different method may work as well or better ?

Ben

[leadman]

I replaced most of the sprue plates on my Lyman molds with the new plates Lyman is now making. They are much thicker metal and seems to remain flatter.
The ones I bought have machining marks in them and vent well. The only problem I have encountered is some of the fill holes aren't cut all the way to the bottom, thus leaving a straight section of holefor the prue to hang in. A counterbore takes care of this.

Also the threaded holes for the sprue bolt lock screw aren't fully threaded. Lyman must use a tapered starting tap and not follow with a bottom tap. When you tighten this screw you think it is tight against the bolt, but it is not. Tap it thru with a bottom tap and the screw stays tight.

[Ben]

leadman :

After reading your post , I thought ....." Gee, When we buy a brand new mold, it is a shame that we have to do all these things to a mold in order for it to work properly."

If we know these things, surely Lyman knows this also, but why don't they correct their problems ?

Quality control with a lot of companies must not be a very high priority.

Ben

[CWME]

I gotta get me a swiss file those bases are AWESOME..

What he said...


Off Topic: That is one funny looking boolet!

[Ben]

Please explain.
How would you file a vent line in a sprue plate?
Maybe scribe some lines?
It is a tiny bit of air so roughing up the plate surface with a course stone or emery cloth would probably let enough air escape. I would smooth the plate after scratching it though.
Of course that would involve a lot of work.
It looks like the small bevel he filed at the top mating edge of the blocks works just fine and is so simple to do. I would have no qualms about venting a mold that way.

Longwood :

I'm like you, I asked earlier for an explanation on exactly how you go about filing a sprue plate with the intent of improving air venting , but as of yet haven't received that clarification ? ?

Ben

[MikeS]

This filing of the sprue plate.....Is this to flatten it more , Is it to roughen it up more and create a mechanism for air to vent ? ? ? Not certain if I understand what the goal is ?

Filing on a sprue plate to allow a mold to vent air is a new one on me.

Ben, what I was saying is to do the filing like you did to the top of the blocks, but to do it on the bottom of the sprue plate. Wouldn't that do the same thing? I'm just thinking that you have 2 mating surfaces, the top of the block, and the bottom of the sprue plate. You're filing vent lines into the top of the block, and I was wondering if instead of doing that, if the same thing couldn't be done by doing the same filing, but to the bottom of the sprue plate instead? Is there some reason that it wouldn't work the same?

Sprue plates are cheap, moulds are not.

[Longwood]

Ben, what I was saying is to do the filing like you did to the top of the blocks, but to do it on the bottom of the sprue plate. Wouldn't that do the same thing? I'm just thinking that you have 2 mating surfaces, the top of the block, and the bottom of the sprue plate. You're filing vent lines into the top of the block, and I was wondering if instead of doing that, if the same thing couldn't be done by doing the same filing, but to the bottom of the sprue plate instead? Is there some reason that it wouldn't work the same?

Sprue plates are cheap, moulds are not.

Mike
I think you are misunderstanding what has been done to the mold.
He has made a tiny vent line, in the mold itself, just under the sprue plate at the top mating edge of the blocks.
Look closely at the photo and you will see a tiny bevel filed into the top edge of each half of the mold.

[MikeS]

Ok, my mistake. I thought he was filing across the top of the blocks to make vent lines.