"Tuning up" my mould really helped.....

[Harry O]

I have a Rapine hollow-base mould that I use for my 41 Long Colt. Now that I am using it for CAS shooting, I am shooting (and casting) a lot more of them. The mould seemed to be getting more balky the more I used it. It was getting so I did not want to cast with it.

The main problem is the bolt/screw that holds the sprue plate on kept loosening. I tried locking it with Red thread locker (supposedly permanent) a couple of times back, but it did not last a full casting session (I believe that the heat killed the Red locker). This time I drilled a hole through the side of the mould, threaded it for 8x40 threads, and put a screw in the hole that I cut flush with the surface of the mould. It held for 3-1/2 hours today without loosening a bit.

The second problem was inconsistent mating between the top of the mould and the sprue plate. Very small, but the feel would change throughout the casting session. Irritating. Depending on the heat, it was sometimes loose, sometimes dragging generally, and sometimes one corner would drag across the top of the mould. There was a small amount of light between the mould top and sprue plate bottom. I ran the bottom of the sprue plate across a new sharpening stone and rounded all the edges on the mould side. Then I checked it with a machined flat block. There was a very slight bend. I put it in a vice and tapped it with a small hammer. After checking several times, it was flat. No drag, and no light showing. It was consistent and smooth throughout the casting session today.

The last problem was the mechanism for the hollow-base pin was binding up more and more when closing (and occasionally on opening). I thought the plate that was supposed to slide back and forth on the bottom of the mould was bent and played with that a while. It was NOT bent. After checking it carefully with a 20x magnifying glass, I saw that one corner of the plate was gouging into the bottom/inside edge of the mould. It had worn a 1/32" (or so) groove in the aluminum mould. I rounded all the edges of the offending plate. That took care of that problem.

What it meant is that I was able to cast 450 bullets in this mould in 3-1/2 hours. That is a record for me with this mould. I had been able to get up to about 100 bullets per hour with practice, but today, I blew that record away. Best of all, the mould was perfectly behaved for all 3-1/2 hours.

Now, to do the same with my other Rapine moulds.

[deltaenterprizes]

Red Loctite is only good up to 350*. For your next mold buy a set screw, you may want or need to remove the sprue plate in the future.

[Harry O]

The screw has a slot in it so that it can be removed with a screwdriver. I did not have any socket head screws with fine enough threads.

[Dale53]

I am a fan of lock screws to hold mold screws (sprue plate screws) tight. However, if you lock "steel on steel" you will damage the threads of the main screw and when you try to move it in or out, will damage the mould threads.

The solution is quite simple. Just drop a lead shot of the appropriate size under the lock screw. It will conform to the threads of the main screw but will protect them from the base of the set screw. It works perfectly, takes no time at all to install and is a permanent fix.

FWIW
Dale53

[mroliver77]

I tell myself I need to treat all new(to me) molds this way. Give them all a once over and be done with it. When I practice this casting is much more pleasurable. I think LBT is the only mold I haven't had to do something to.
Jay

[No_1]

Great advice Dale!

Robert

I am a fan of lock screws to hold mold screws (sprue plate screws) tight. However, if you lock "steel on steel" you will damage the threads of the main screw and when you try to move it in or out, will damage the mould threads.

The solution is quite simple. Just drop a lead shot of the appropriate size under the lock screw. It will conform to the threads of the main screw but will protect them from the base of the set screw. It works perfectly, takes no time at all to install and is a permanent fix.

FWIW
Dale53