Printable View
This is an offshoot of a thread I started in the Lead Alloy forum:https://castboolits.gunloads.com/sho...with-new-alloy
The basic problem being that I am experiencing about 5% rejects due to voids at the sprue across three different molds. This is alloy that I made up for the first time due to a lack of lead wheel weights in Maine.
Has anyone else experienced this issue using their Master Caster?
the puddle is not big enough on top of the spru plate and sometimes one cavity fills faster then the other . Best way let the the puddle connect the two cavity together , and also cutting off the spru to soon will tear and create a hole . But I would not worry about the 5 % rejection rate , you will get some defects . I use 50 50 wheel weight and flashing for all my plinking loads then powder coat .
I have run into this problem but my Master Caster is automated.Quote:
Originally Posted by BD
Initially when I set up the machine, I set lead pour to fill the mold and put a really small "hershey kiss" on the sprue (upside down)
Well have casting 1/2 a pot I started noticing holes in the base of the boolit. Voids.
This had to do with the flow of the lead at a 1/2 pot vs full pot.
There is less weight pushing down so the pressure is less.
Less pressure means less flow. A lead pot that is full flows more lead in a 1/2 second then a lead pot that is 1/2 full. This, of course, is with all other factors being the same (alloy, temp)
To correct the flow rate I have been filling the sprue to the max level when the pot is full.
Typically I put a 5 lb ingot in whenever there is space in the pot. I normally don't have to stop and let the pot heat back up.
Thanks for the replies. I make it a point to have the sprues connect, (I have a can setup below the machine just to catch the occasional spillage from that). and I always keep the pot above 3/4 full. I cast with the next three ingots pre-heating on the rim of the pot and I tip them in as soon as there's room. I keep 1/2" of clay kitty litter on top of the melt and the ingots settle through that layer pretty cleanly. One quick stir and they're in the melt. It's frustrating as I've been running this machine about 20 years with WW alloy and haven't had any issues like this where I need to look through the results individually. I've had the odd cavity that didn't fill, but they were very obvious and only amounted to 3 or 4 rejects out of a thousand at the most. 5% rejects seems like a lot to me.
I had slow freezing bullets one time with torn out pits the lead had not froze yet. turned our to be a very high amount of Tin maybe send out a sample and get a test?
I had bought some double end 38 wadcutters from an indoor range I use to belong too and was shooting 2.7 grains of Bullseye in 38 Special cases. They leaded my bore really really bad on a revolver that never did that. Talked to the owner and apparently they must have gotten a lot of similar calls because he said "Yeah the guy that casts them felt that if tin was good why not put a whole bunch more in". So have you shot any and did they lead the barrel more the usual?Quote:
Originally Posted by bruce381
Is this a case where the OP needs better venting at between the mold blocks and the sprue plate?
I'm not sure what's up here, as I've replied to this thread twice now and neither one showed up.
I don't think it's an issue with venting on the mold as three different molds exhibited the same issue, only one of them was new, and I've dropped 180,000 or so out of the #68 style mold which came used with the machine when I bought it back in the '90s.
Here is the correspondence from BNE:XRF Data First:
Pb = 95.2%
Sb = 3.3%
Sn = 1.5%
I scanned in multiple places and even cut into the pore and measured down into the pore. All of the measurements were essentially the same. (If you have any experience with analytical equipment, there is always some variation, but it was really close in all of the areas tested.) I scanned for other elements and none showed any "peaks". If you have a contaminant, it is tiny.
That being said the "pore" is huge. One was at least 0.25" into the base of the bullet. I took the two uncoated bullets and looked at them under a microscope. It was interesting, the outside of the bullets do not show the normal cooling wrinkles characteristic of a cold mold, but under a microscope you could see circular patterns in the base of the bullet - near the pore. I am not familiar with how a master caster works, so I am curious about the sprue plate temperature.
I came home and read through your post and all of your following comments. My theory is a s follows:
1) You do not have an alloy problem. Why?
If it was alloy - the pores would be randomly found in or on the bullet.
Running the melt hotter would not magically make the problem go away.
I also think I would have found SOMETHING that looked wrong under the microscope and then the XrF. (I've spent the last 30+ years in a very technical field and have done a fair amount of analytical work.)
2) I think it is a temperature problem. ("But I did everything the same!" - You said something to that effect.)
You very well might have done EXACTLY the same thing, but some variables may be present that I can only guess about.
- Thermocouples and heating elements DRIFT. Furnace heating elements tend to produce LESS heat over time given the same power input. Thermocouples also drift. (Typically downwards.)
- The alloy is different. Not contaminated per se, but different, therefore the melting point and the viscosity are different.
I should have asked you to send some of the "Good" bullets. I suspect the circular patterns would be less visible.
I hope this helps. My opinions are free - you can use them as you see fit!!
BNE
Quote Originally Posted by BD - Yesterday 11:55 PM
Thanks for the analysis, and the theory. The last run I cast at 800 degrees, and still had some voids at the sprue, (although they were much smaller). I think 1.5% is light on the tin and I am going to sweeten it up a bit before I cast more hoping to get back on my 6 second cycle. At 800 I have to leave the mold under the spouts for a full three seconds, and then cool it for 4 more seconds before I cut the sprue or I get smearing on the mold top.