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Author Topic: Sand cast parts.  (Read 4076 times)

Sam Everly

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Sand cast parts.
« on: August 25, 2010, 05:48:22 AM »
I have a trigger guard and butt plate that i want to have some copys made off of. My question is how much will the new copys shrink. I guess i can call the foundry where i am going to have them sand cast at and ask them . They know what they are doing on gun parts, Earl Lanning gave me there info and they do work for him . Best of all they are only about 30 miles from the house.     
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Offline Dave B

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Re: Sand cast parts.
« Reply #1 on: August 25, 2010, 08:20:54 AM »
If I remember correctly it is about 2-3% shrinkage with yellow brass. I looked up the shrink rate for brass and it says allow for 3/16 shrinkage per foot of length.  I watched Dave Rase casting some trigger guards as well as small router plane bodies. The brass used was old key blanks from a lock smith shop and other scrap brass. The  first pattern for the Router plane was from a member of the gun-making class they had been running. He had the plane in his tool box, His father had made the plane being a tool & die maker.  I rammed up the mold several times and Dave poured the brass. Several patterns used the second and third times were cleaned up first generation castings. You could lay them side by side and see the down sizing very clearly. 

I have heard about the enlargement of the patterns using layers of Masking tape. This will build up the volume to be lost as well as breadth. Some of the trigger guards they cast  were pretty thin after pouring. The trigger guard was slim to start with.
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Dave Blaisdell

Offline Randall Steffy

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Re: Sand cast parts.
« Reply #2 on: August 25, 2010, 01:33:48 PM »
I can confirm 1.5% or 3/16" per foot as the typical shrinkage for brass. Enjoy the casting!
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Offline Acer Saccharum

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    • Thomas A Curran
Re: Sand cast parts.
« Reply #3 on: August 25, 2010, 03:45:04 PM »
Yup, 3/16 per foot.
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Offline Robby

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Re: Sand cast parts.
« Reply #4 on: August 25, 2010, 06:07:42 PM »
I have an old, L.S.S.Co.(Starret) pattern makers one foot ruler. It is marked out as though it were One foot, by 1/8's, 1/16's, 1/32's, 1/64's on its four edges, but is really one foot three sixteenth inches, and stamped SHRINK 3-16 TO FOOT. The shrink factor is built in. Pretty cool!
Robby
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molon labe
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Offline Randall Steffy

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Re: Sand cast parts.
« Reply #5 on: August 25, 2010, 07:41:52 PM »
Patternmakers use those shrink rulers every day, still. Different rulers for different metals. Maleable iron 1/8", aluminum 5/32"and in some cases with double shrinkage circumstances you may use up to 3/8" per foot. Fun stuff.
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bigsky

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Re: Sand cast parts.
« Reply #6 on: August 25, 2010, 08:33:06 PM »
I have heard that dipping the part in paraffin before making the mold increases the dimensions enough to compensate for shrinkage.
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Offline Acer Saccharum

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    • Thomas A Curran
Re: Sand cast parts.
« Reply #7 on: August 25, 2010, 08:58:11 PM »
Double dipping is not allowed, however.
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Ramrod scrapers are all sold out.
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