Proper flat washer orientation
Proper flat washer orientation
(OP)
I found some information in thread404-198093: Proper Flat Washer Installation but it doesn't completely cover my application and am wondering what others think about this question...
I build lasers for everything from medical to military applications and we always use split lock washers and flat washers on all our screws. Lately (ever since I came back to work here) we've been getting lower quality (ie. cheaper) stamped flat washers that have a radiused top and a sharp bottom edge where they've been stamped from a sheet of stainless. Production personnel consistently place the sharp outer edge down causing it to bite into the material being fastened, be it anodized aluminum, stainless, or printed circuit boards. I say this is incorrect, because of the damage, albeit cosmetic, that is being done to the underlying material and the washers should be turned "upside down" so the radiused side is in contact with the material being fastened. The lock washer OD is smaller than the diameter of this stamped edge so it does not interfere with the lock washer.
Am I just being anal about something that has little significance, or do you feel there is a method to my madness? My only arguments for my approach are that the washers do damage the surface under them if positioned edge down, and when disassembled, they will stick to what was underneath them.
Thanks for your comments!
-Scott
I build lasers for everything from medical to military applications and we always use split lock washers and flat washers on all our screws. Lately (ever since I came back to work here) we've been getting lower quality (ie. cheaper) stamped flat washers that have a radiused top and a sharp bottom edge where they've been stamped from a sheet of stainless. Production personnel consistently place the sharp outer edge down causing it to bite into the material being fastened, be it anodized aluminum, stainless, or printed circuit boards. I say this is incorrect, because of the damage, albeit cosmetic, that is being done to the underlying material and the washers should be turned "upside down" so the radiused side is in contact with the material being fastened. The lock washer OD is smaller than the diameter of this stamped edge so it does not interfere with the lock washer.
Am I just being anal about something that has little significance, or do you feel there is a method to my madness? My only arguments for my approach are that the washers do damage the surface under them if positioned edge down, and when disassembled, they will stick to what was underneath them.
Thanks for your comments!
-Scott





RE: Proper flat washer orientation
But don't expect much success. Lockwashers are pretty much cosmetic anyway, they work very, very poorly in the real world, though most designs include them "because everybody does" ... Best retention is the double-sided washer pairs that prevent the nut from backing off. (Nordlock is the best, but they are expensive.) Beware of cheap Nordlock imitations!
Almost everybody thinks that the "gouging" of the substrate is a "good thing" because it "catches" the washer and (seems to) prevent movement of the bolt and nut. Also, it "looks prettier" and "more professional" even though putting the washer on that way may harm the substrate in your case.
RE: Proper flat washer orientation
RE: Proper flat washer orientation
Call out a MS or NAS part from another supplier.
Chris, CSWA
SolidWorks 13
ctopher's home
SolidWorks Legion
RE: Proper flat washer orientation
RE: Proper flat washer orientation
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Proper flat washer orientation
I doubt btrueblood's suggestion is cost effective (you also need media, square footage in your plant and electricity), but it's certainly worth mentioning.
RE: Proper flat washer orientation
I don't think I've seen any sharp enough to hurt someone, but the stress concentration is enough to damage the paint, starting a corrosion path directly where it can't be easily seen.
Instructions can be tried, but they won't work long. There's eventually someone who figures it's just wrong and will 'fix' it for you. The best is to use hardware that can be reversed without causing any problems so no special instructions are required.
RE: Proper flat washer orientation
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Proper flat washer orientation
Thanks once again for all the quick responses!
RE: Proper flat washer orientation
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Proper flat washer orientation
Specifically, pieces of the burred edges will fall off and get in your optics or your precise mechanical bits.
If installed 'up', someone will get scratched, and curse you for being a lazy bastard.
If installed 'down', the burrs will scratch or scar the expensive finish you applied, and someone will find the scars or scratches, deduce the source, and call you a cheap, sloppy bastard.
If you can't get the bean counters to buy better quality washers in the interest of keeping their evil jobs, other tactics exist:
If you specify somewhat thicker washers, they will have sturdier burrs on them that may do less damage, or be easier to strain out of the vibratory finisher should you elect to deburr the washers in house.
If you double or triple the washer thickness, the burrs may actually break off in the stamping die, becoming the washer supplier's problem, as they should be.
Mike Halloran
Pembroke Pines, FL, USA
RE: Proper flat washer orientation
RE: Proper flat washer orientation
RE: Proper flat washer orientation
Plan your career accordingly.
Mike Halloran
Pembroke Pines, FL, USA
RE: Proper flat washer orientation
Quando Omni Flunkus Moritati
RE: Proper flat washer orientation
Like ctopher suggested above, the wise thing to do would be spending an extra 1 cent per washer to get a burr-free product. The AN960 washers shown in the linked spec are commercially available in stainless steel for about 3-4 cents each.
Good luck to you.
Terry
RE: Proper flat washer orientation
To point to the bad things sometimes done by shabby thin washers and then write manufacturing standards banning washers based on ST washers deficiencies is most unfortunate.
RE: Proper flat washer orientation
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.