zinc electroplated fasteners
zinc electroplated fasteners
(OP)
Hi guys,
Quick question. Was purchasing M8x1x70 8.8 fine threaded fasteners for a project at a local supplier yesterday and could only get them uncoated (actually black) and not zinc electoplated. I was told that it was because the zinc coat would interfere with proper fit, although are not hot dipped. I already had fine threaded zinc electoplated nuts for them, so was wondering if the supplier's story is legit. Anyone know about this?
Also, what exactly is the black coat? I thought the zinc electoplating was only in the single digit micrometers and didnt affect the tolerances much, but could be wrong about this. Anyone care to correct me?
Thanks!
Quick question. Was purchasing M8x1x70 8.8 fine threaded fasteners for a project at a local supplier yesterday and could only get them uncoated (actually black) and not zinc electoplated. I was told that it was because the zinc coat would interfere with proper fit, although are not hot dipped. I already had fine threaded zinc electoplated nuts for them, so was wondering if the supplier's story is legit. Anyone know about this?
Also, what exactly is the black coat? I thought the zinc electoplating was only in the single digit micrometers and didnt affect the tolerances much, but could be wrong about this. Anyone care to correct me?
Thanks!





RE: zinc electroplated fasteners
If I remember correctly.
It is possible to get zinc plated fasteners in most common sizes etc. I forget the exact wording in the ASME B1.1 but there is some allowance made, at least on class 2 if I recall correctly.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: zinc electroplated fasteners
It's possible to get any thickness (within reason) plating.
It's possible for the fastener manufacturer to roll the parts slightly under size to accommodate a known plating thickness.
The plating process can cause hydrogen embrittlement, which on grade 8.8 fasteners may lead to cracks and failure. Proper post-plating heat treatment can remove the hydrogen and alleviate the problem. However it's often not done, or not done correctly. So clued in buyers requires lots of extra certs and traceability.
You need to find a more knowledgeable supplier.
RE: zinc electroplated fasteners
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RE: zinc electroplated fasteners
thanks for the responses. Yeah I figured that it didn't make much sense. The supplier is a large fastener supplier based in a neighboring country (I'm in Europe) but they have a local store here about 15 mins from my work so I made the trek over there. They didn't have the M8x1x80 screws I was looking for with zinc plating, only 8.8 black oxide and stainless. The lady working there claimed that it was because the coating would be too thick and the parts wouldn't fit together - which didn't make any sense to me, but I went ahead and bought the black oxide screws. Another fastener supplier that we ordered from also did not have them available, it was the only part on our list that they couldn't get for us, and they will usually find the parts if they don't have them in stock. That's why I was curious if maybe these just don't exist, but obviously they do.
Thanks for the info.
RE: zinc electroplated fasteners
Regards,
Cockroach
RE: zinc electroplated fasteners
Note that this was 30+ years ago so this is not something new, zinc-plated fasteners have been around for years.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
http://www.siemens.com/plm
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