Having a little trouble . I casting with pure Linotype. The sprue tears out instead cutting off smooth. I've moved the pot tempature up and down. I changed the cool down time of thesprue. I sharpened the sprue plate. The mould works fine with 20/1. Any ideas ?
Having a little trouble
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- Last Post 25 January 2015
While linotype goes from the liquid phase to solid phase without a “pasty” or plastic intermediate period, it is not very strong until it gets fairly cool. My first suggestion is wait 5 /10 seconds longer before you cut. Secondly, if you are cutting with a mallet or striker, you may not be putting enough down force on the plate to stop it from riding up and pulling metal out of the base. I cast lots of linotype bullets, and they are harder to get perfect bases than softer alloys. HTH, Ric
20:1 and Linotype have very different cooling rates and cooling characteristics. I wouldn't expect them to behave the same at sprue cutting.
I have really changed my sprue cutting method over the years and do it much differently than when I was a boy.
I treat every alloy the same by basing my sprue cutting time on the cooling stage of each alloy through observing it very closely.
My preferred and most successful results are achieved by using a leather gloved hand to open the cutter plate with a downward pressure while opening the cutter plate at the very first sign of hardening crystallization on the sprue puddle. Big sprue puddles are important to keep the mold temp up and also make it easier to see the hardening crystallization wave at it's first appearance. Then I open the cutter immediately but wait 5 more seconds before I open the mold. This gives a smooth flush cut for me.
If the lead smears on the cutter plate, you are opening too soon. Clean the plate with heat and a brass brush and apply an anti-flux like pencil lead scribbled on. When you get your timing perfected, your cuts will be smooth and flush.
What Onondaga said, and plus one for just doing it with leather gloves! Especially if you have Lee molds, it's easier on the mold, and even with steel molds the less vibration/impact you have the longer the sprue plate screw will stay tight.
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