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Antique Safes/Acorn Finial Screw Thread Mystery

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Expert: - 1/7/2009


Question

Safe
Hi,
On my own, I am trying to restore my safe, probably a Herring-Hall Marvin
Safe from about 1920.   My safe is missing the top acorn finials from both
hinges and I have located a machinist who will make an entire set of new
ones out of brass or aluminum.  The existing finials screw in to the hinge
and the thread diameter is 1/2 inch.  Strangely, the screw in thread diameter
for the top (missing) finials is larger than 1/2 inch. Even stranger,  the thread
diameter is also less than 9/16 (.5625"), the next closest US size bolt I could
find.  My calipers read somewhere between .51 to .53 when I measure the
threaded hole for these missing acorns.  Does that the thread size I am
seeking is 17/32?   I tried to screw in metric bolts but I can't find any match
and the use of metric threads in a 1920 US safe doesn't make sense anyway.  
Additionally,  I cannot find a 17/32 bolt anywhere to even try to screw in to
verify that the thread diameter is 17/32.  Why would the original safe hinge
maker employ such an odd thread size? Do you have any insight that might
shed light on this mystery or maybe you can recommend what I can do.  The
machinist wants me to specify a thread size for these upper acorn finials.

Answer
Stephen,

Many of the Acorn threads were hand made.  I'm having the same problem with a MacNeale & Urban from the early 1900s.  I wish I could help with this one, but I run into this problem almost daily and the only solution is to make it as close as possible on a lathe.  You are not going to find a standard size tap & die to work.

Unfortunately, there are no records available on "how & why" the safe manufactures had such a variation in thread sizing for Acorns.  The manufactures didn't even have a standard on their own safes, between different models.

My recommendation is to figure out what the thread is (TPI), and then use a slightly smaller diameter screw size.  For instance if you are looking at the 17/32" - use the 1/2".  Its Ok if the Acorns are slightly loose when screwing in, what you need is for them to tighten up when it is all the way in.

Tell the machinist to quit being such a cry baby!  "just joking"!

Andy

Terry V Andreasen (Andy)

Expertise

Safe and Vault related Questions; Antique Safe Repair and Restoration; With over 40 years in the Safe & Vault industry, if I can't answer your question I know where to get the answer. Current Project: Restoration of two Tilton & McFarland Safes from the 1860's. Will answer Safe & Vault related questions concerning age, value, restoration, moving, opening & repairing, parts, operation and history. Note: It is not my intention to teach you to open safes or to provide information which may aid in the unlawful opening of a safe. I will not give out drill points or information which I deem inappropriate.

Experience

40 years in the Safe & Vault Industry. Service Manager for one of the largest Safe & Vault companies on the West Coast. Graduate of Lockmasters Safe Lock Servicing, Safe lock Manipulation and Safe Deposit Lock Courses. Graduate of Locksmith Institute. Certified Instructor for the California Locksmith Association teaching Basic and Advanced Lock Servicing, Basic Safe opening and Repairing. Factory Trained by AMSEC, LORD Safes, LeFebure, Mosler, KabaMas, LaGard and Sargent & Greenleaf

Organizations
Safecrackers International and the National Antique Safe Association

Education/Credentials
Graduate of Locksmith Institute 1972 Graduate Lockmasters Safe Lock Servicing 1974 Graduate Lockmasters Safe Lock Manipulation 1975 Graduate Lockmasters Safe Deposit Lock Servicing 1985 Instructor Certified - California Locksmith Association - 1985 Factory trained by AMSEC, MAJOR, STAR, Johnson-Pacific, Kaba-MAS, Allied-Gary, ISM, Lord, Brown Safe, EXL, Mosler, Diebold.

Awards and Honors
2009, 2010 & 2011 Listed in AllExperts top 50 Experts. All Experts Categories - Safes & Security Containers, Locksmithing, Antique Safes. Retired US Army Reserve Chief Warrant Officer (CW3), with 32 years of total service. With numerous awards from Vietnam, Desert Storm and Operation Iraqi Freedom. US Navy - 1971-1981 US Army Reserve 1984-2006 US Army Retired Reserve 2006-present

Past/Present Clients
US Secret Service, FBI, BATF, Local Law enforcment agencies, Diebold, Hamilton Pacific, Red Hawk Int., Chubb International, Bank of America, Wells Fargo Bank, Mechanics Bank, El Dorado Savings Bank, many Credit unions and smaller banks. McDonalds, Togos, BurgerKing, TacoBell, Carls Jr. FoodMaxx, SaveMart, Lucky's, Albertson's, Raley's, Safeway, NobHill, Bell Markets, PW Markets. Great America, Century Theatres, Cinemark Theatres, UA Cinemas, and many homeowners and small businesses. Provide warranty service for lock and safe manufactures. Service area is Northern California - Fresno to Oregon, including western Nevada

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