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Flat washer holes

M

mkirsch

Well-known Member
Why are the holes in flat washers one size too large?

It's always something that I've wondered about...

Go to Home Depot, or any hardware store. Take a flat washer out of the 3/8" bin. Take a bolt from the 7/16" bin. The 7/16" bolt will fit through the hole of the 3/8" washer 9 times out of 10.
 
I've long thought it was due to the stockers placing the washers in the wrong bins. I regularly buy one size too small for this very reason.

Dean
 

I usually just put the bolt that I need the flat washer for in my pocket before I head to town, and then pick out the size of flat washer that FITS the bolt, which is usually one size smaller than what the washer is supposed to fit.
 
Hello mkirsh,
The wahers that fit sloppy on the bolt are made for non critical applitions, where no torque is required. They are not always the same I.D., as you found out, for that reason. For applications where a torque is required, the 3/8 fastener-bolt will have a 3/8 washer, and it is also hardened to help maintain the torque applied to the bolt.
Guido.
 
Yabbut what do you do for 1/4 inch? lol
Been doin' the same thing for years.
Finally found a place with 1/4 FW but they were plain and oil soaked. Bought several lbs.
 
I have been using the wrong sized ones for years in order to get a decent fit. If you don't need a large od the grade 8 SAE ones are smaller inside and out too.

Likely just another case of poor quailty in everything made now.
 
I work for my local cooperative, and we put a bolt, washer, and nut bin in our store 3 years ago. We ordered the bins, placards, and parts from one company, received same, and loaded all the bins...What comes out of the box is what we put in the bins...if it fits loose, so be it, buy the next smaller (tagged) size if that is what it takes, but don't blame it on the person that stocks the bins...
 
That's just the way gr2 washers are, not a problem for most applications. If you want a tighter fit then buy more expensive ones, they are available!
 
It all depends on what standard the particular flat washers that are stocked where you buy them were manufactured to. For example, a 3/8 washer manufactured to American National Standard (ANSI) B18.22.1 would have an inside diameter (nominal) of 0.406 inches. A 5/16 washer manufactured to that same standard would have a nominal inside diameter of 0.375 inches for a type A washer and 0.344 inches for a type B washer. So some 5/16 washers per that standard would fit snugly on a 3/8 bolt and some wouldn't fit at all. In contrast all flat washers manufactured to Society of Automotive Engineers (SAE) standard J488, would fit snugly on the same size bolt; that is a 5/16 washer for a 5/16 bolt and a 3/8 washer for a 3/8 bolt.
 
The washers you are referring to are the USS standard. The course threads on bolts is also a USS standard. You can get tighter fit flat washers if you spec. SAE standard. If you want an even closer fit ask for the AN aircraft standard. I buy the under size washer to to fit the bolt. Number 12 on a 1/4", 1/4" on a 5/16", 5/16" on a 3/8" and so on.

Kent
 
If I want an exact fit I purchase SAE washers,
also:-they are FLAT. Some of the cheap grade 2
washers at the farm supply stores are uneven,
thicker on one side that the other--like some
mom and Pop machine shop in China is buying our
scrap and having the kids punch them out on a
cheap press in the backyard !
 
I use a lot of 3/8x 3.5 carriage bolts building picnic tables.I find plenty of 3.5 in the 3 inch and 4 inch bins.Customers mix them up.
 
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