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Re: interchangable parts?
Posted by John S. on Sunday, 5 October 2014, at 12:08 a.m., in response to interchangable parts?, posted by Rick Baker on Saturday, 4 October 2014, at 9:43 p.m.
You are correct that many of the U.S. martial arms screws are similar or in some cases identical. There is an old Springfield Armory table showing which parts are interchangeable between various models, mainly trapdoor era, and I am sure someone will post a link to it.
The small trigger guard wood screws first appeared on the Model 1855 .58 caliber rifle musket, and was unchanged through the trapdoor and I believe the Krag era. Sometime in the M1903 era the slot was slightly changed from a curved radius at the bottom to a flat bottom (note the slightly rounded tip on screwdriver tools). This small wood screw was used on Krag but swivels and buttplate tangs, and last used on the M1 Carbine buttplate and one of the M1 Garand buttplate screws.
The trapdoor lock internal screws are identical to the M1855 and later rifle musket lock screws, except for length as lockplate thickness differed, and the exposed tip surface being polished or blue for appearance. Slight variations of these lock screws (length and slightly rounding of the edges of the head) were used on the bands of the Krag and M1903 rifles.
The lock screws were .187 x 26 threads per inch (as I recall) and this was a non-standard size which was phased out by the M1917 Enfields which used a no. 10 x 32 TPI screw for swivels and bands, and the M1903A3 which also used no. 10 x 32 TPI screws on the bands for swivels.
Why? Probably to cut costs for tooling for different types of screws and permit the use or modification of stock on hand. Or, maybe as new models were developed, the developers simply used parts close at hand, and the new model ended up being adopted with some parts borrowed from older arms.
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