Just what is the difference between a 1/4 20 screw and a 1/4 in coarse screw? I was looking for some 1/4 20 2 1/2 inch nylon screws for my wing hold downs and couldn`t find any at the hobby shop or any of the building supply places. I did find one 1/4 coarse at Home Depot and guess what, it seems to work good in the 1/4 20 threads in the wood blocks.
Machine screws are available (generally) in coarse and fine thread pitches, with some sizes having an 'extra fine' pitch as well.
In the US, the pitches are SAE (Society of Automotive Engineers).
SAE 1/4 inch pitches are 20, 28, and 32 threads per inch (TPI).
1/4-20 is the TPI of choice for wing bolts as the finer threads don't do well in wood.Never seen 28 or 32 pitches in nylon.
Cheers, Fred McClellan the dash plumber at mindspring dot com
1/4-20 IS a coarse thread. Most nylon wing bolts are 1/4-20 TPI. (20 threads per inch) 1/4-28 is the standard fine thread, and used for prop shafts. 1/4-32 is finer, and used in glo-plugs. 1/4-40 is extremely fine and pretty scarce. I have a tap, but forget what I got it for. :-\
Bob
They are the same.
Checkout
They also have 100 count bags of various size nylon screws including
1/4-20 for a $1 or $2 a bag.They have good prices and same day shipp>Just what is the difference between a 1/4 20 screw and a 1/4 in coarse screw?
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