The Shop > Metal Stuff
Oil fired crucible furnace
awemawson:
Steve,
I used to use a 'Speedy Moisture Meter' to test my sand - not every time but reasonably regularly, as I didn't cast often enough to do it by judgement. They turn up on eBay fairly regularly.
tom osselton:
Found this at http://www.foundry101.com/archive.htm
Sand mixture for iron and steel casting is LESS than 5% bentonite and 70 grit. Sea coal is also added to prevent burn ln.
I just looked at your pic "the shake out" on page 1. I see the sprue with the two gates connecting the block but I don't see a riser might be reducing the venting.
Tom
RussellT:
Your comments on the skill of casting radiators reminded me of window frames.
A friend was involved with the restoration of an old (19thC) industrial building and the original window frames were cast iron with small panes of glass. Some of them were damaged and so they wanted some new ones cast. Unfortunately they struggled to find anyone who could cast them!
I'm impressed with your determination on iron casting, I'm sure your hard work will pay off with good castings soon.
Russell
vtsteam:
--- Quote from: awemawson on July 26, 2013, 04:15:14 AM ---Steve,
I used to use a 'Speedy Moisture Meter' to test my sand - not every time but reasonably regularly, as I didn't cast often enough to do it by judgement. They turn up on eBay fairly regularly.
--- End quote ---
Andrew thank you for that suggestion.
I'm thinking that weighing a sample of greensand on my gram scale before putting in an oven to dry at low temp and then re-weighing would work, too. I might do that just to get an idea where I am with sand that I think "feels" right. Might be some surprises there.....
vtsteam:
--- Quote from: tom osselton on July 26, 2013, 04:38:31 AM ---Found this at http://www.foundry101.com/archive.htm
Sand mixture for iron and steel casting is LESS than 5% bentonite and 70 grit. Sea coal is also added to prevent burn ln.
I just looked at your pic "the shake out" on page 1. I see the sprue with the two gates connecting the block but I don't see a riser might be reducing the venting.
Tom
--- End quote ---
Tom thanks for the reference. I'd seen that before, and I notice they don't actually cast iron.
They also have two references on their site like the one you quote -- one says "UNDER 4%" and the other says "UNDER 5%". My take on that site is that they are very nice people and do a good job of popularizing hobby aluminum casting craft with copies of pre-existing objects as patterns, but they aren't really a good technical resource.
I've seen references to a range of bentonite by both technical commercial sources as well as people who have decades of experience in iron casting., like Ironman, Stewart Marshall, and others. 7 or 8% is well within that range. Bentonite is also not just a single chemical substance. there is western and southern bentonite, with different properties, calcium bentonite and sodium bentonite. These can also be blended.
Right now I'm trying to figure out what kind I have. It is labeled "Whittaker" and "Bentonite 149". I've found just a few references connected with those -- one shows more sodium than calcium, so I'm currently guessing it is sodium bentonite.
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