This is really interesting!

[MikeB]

I picked up what appears to be mold for making a Columbia support arm and associated parts. (I am guessing maybe a Columbia AY.) I expected this to be a two-piece mold, but it's all a single piece. There are what appear to be tubes that lead to the parts, presumably to feed the molten material inside to make the part. There is a hole in the center of the tubes that looks like it's plugged - or perhaps a part was already made and it is still inside of the mold. The mold itself is quite heavy. Not sure if it's steel or aluminum. I have no idea how one would get the mold apart once the part was made, and I don't know if this was a mold for making original parts, or something that was used to make repro parts later on.

Not interested in selling this. Just curious about what people thought of it. I think that it's definitely one of the more interesting phonograph-related items I've seen. I'd be happy to being it to the APS if anyone wants to have a look at it in person.

[Curt A]

This looks (to me, anyway) like an original casting mold, which should have had a second half. The tree like channels are called runners. The system normally consists of a vertical section (downgate or sprue), where molten metal enters the mold, to the point where it joins the mold cavity (gate) and leads from the mold cavity through vertical channels (risers or feeders). The detail and construction are what makes me think it is an original factory mold. It's extremely well made and very interesting. Where did you find it?

After looking at it again, it appears that the cast parts haven't been removed, since the positive images should be the actual parts - the mold should be a reverse image... and the horn cradle shows as a positive design on both sides.

PS: That striped thing looks very much like a cat...

[MikeB]

This looks (to me, anyway) like an original casting mold, which should have had a second half. The tree like channels are called runners. The system normally consists of a vertical section (downgate or sprue), where molten metal enters the mold, to the point where it joins the mold cavity (gate) and leads from the mold cavity through vertical channels (risers or feeders). The detail and construction are what makes me think it is an original factory mold. It's extremely well made and very interesting. Where did you find it?

After looking at it again, it appears that the cast parts haven't been removed, since the positive images should be the actual parts - the mold should be a reverse image... and the horn cradle shows as a positive design on both sides.

PS: That striped thing looks very much like a cat...

Thanks, Curt. I kept thinking that there has to be a second half to this mold, but yes, it looks like the entire parts are contained within this one piece, which again begs the question, how would they have gotten the parts out of there? Acquired from an "online auction."

The Striped Thing always has to check out whatever is new in the house.

[physicist]

I think it's a pattern for 2 part sand casting. Each side is used to form a negative mould in two sand boxes. These are then put together
and molten metal poured in through gate/runners to form the part.

It would make these:-

columbia.jpg (15.9 KiB) Viewed 679 times

[MikeB]

I think it's a pattern for 2 part sand casting. Each side is used to form a negative mould in two sand boxes. These are then put together
and molten metal poured in through gate/runners to form the part.

It would make these:-
columbia.jpg

I see. So rather than being a mold, it might have been used to make a negative image for one-half of a mold. The projection on the rear could have acted as a handle or anchoring point to press it into the sand.

[physicist]

I see. So rather than being a mold, it might have been used to make a negative image for one-half of a mold.

No - you use both sides of it - it makes both halves of the mould.

The "handle" actually forms the gate through which the metal is poured.

[MikeB]

I see. So rather than being a mold, it might have been used to make a negative image for one-half of a mold.

No - you use both sides of it - it makes both halves of the mould.

The "handle" actually forms the gate through which the metal is poured.

I can see that now. Thank you.

[edisonclassm]

Physicist is exactly right. It is what is known as a pattern plate. Somewhat costly to make for such a small run of parts. It is better when making a short run just to use an original part. You will end up with a small shrink but it is usually tolerable. I've used this process for years with great success. BTW you said you got it at an online auction. Where was it located? I'm curious.

[Curt A]

Thanks for clearing this up... I was thinking a mold, but I knew a lot of parts were sand cast, now it makes sense that it appears positive on both sides as a pattern for sand casting... I still think that it's an original piece from the factory. It would be interesting to discover where the auction obtained it.

[MikeB]

Thanks for clearing this up... I was thinking a mold, but I knew a lot of parts were sand cast, now it makes sense that it appears positive on both sides as a pattern for sand casting... I still think that it's an original piece from the factory. It would be interesting to discover where the auction obtained it.

Indeed. I'll try and find out more information about where it came from.