'GO' & 'NO GO' Thread Plug Gage Standard

  • Thread starter qualitytoughnut - 2010
  • Start date
U

Umang Vidyarthi

Sometimes. In practical terms, plating rarely builds up enough inside threaded holes to make any difference in terms of corrosion protection anyway. Sometimes the purpose of plating is decorative or cosmetic and isn't intended to provide corrosion protection. This is often true of chrome plating on zinc castings.

Permit me to disagree with you on this Jim.When we give a surface plating
of 6 to 7 microns;the threaded portion recieves 10 to 12 microns(at the apex of thread),blocking the penetration;that is why there are two grades of gages with G & H marking I have referred to in earlier post.Here we are not talking about decorative coat,but about a corrosion resistance,since the sea journey in export consumes about 45 days!I being over protective,give lacquer quoting over the plating to combat corrosion.

/Umang
 
Last edited by a moderator:

Jim Wynne

Leader
Admin
Permit me to disagree with you on this Jim.When we give a surface plating
of 6 to 7 microns;the threaded portion recieves 10 to 12 microns,blocking the penetration;that is why there are two grades of gages with G & H marking I have referred to in earlier post.

It really depends on the application. If there is a problem with plating buildup, it's likely to be limited to the first couple of threads. Plating has a tendency to buildup in areas of high current density, and this includes the peaks of threads. In practical terms, plating rarely penetrates far enough into a hole to make a difference, and when it does, it usually means that the parts have spent too much time in the bath. As far as "G" and "H" designations go, those are metric thread classes, roughly analogous to designations such as "2B" in English threads. While they might be useful in preplate/post-plate situations, they are not intended for that purpose.

Here we are not talking about decorative coat,but about a corrosion resistance,since the sea journey in export consumes about 45 days!I being over protective,give lacquer quoting over the plating to combat corrosion.

The question was whether or not thread-chasing could breech a deposition intended for corrosion protection. I answered in the affirmative, but added that sometimes plating is used for purposes other than corrosion protection. By and large, zinc castings don't need corrosion protection. In cases where one is unsure about whether or not a protective deposition has been compromised, it's best to err on the side of caution, and/or do corrosion testing (salt spray, e.g.) to confirm the integrity of the deposit.

As for lacquer coating, if it's called for in the specifications that's fine, but it also presents an issue with buildup, perhaps more so than plating, because it's more likely to run into cavities.
 
U

Umang Vidyarthi

It really depends on the application. If there is a problem with plating buildup, it's likely to be limited to the first couple of threads. Plating has a tendency to buildup in areas of high current density, and this includes the peaks of threads. In practical terms, plating rarely penetrates far enough into a hole to make a difference, and when it does, it usually means that the parts have spent too much time in the bath. As far as "G" and "H" designations go, those are metric thread classes, roughly analogous to designations such as "2B" in English threads. While they might be useful in preplate/post-plate situations, they are not intended for that purpose.

You are right Jim,and this exactly is what I have stated in my post.

2.I am unable to comprehend your last sentence,could you please throw light on intended purpose(s).

/Umang
 

Stijloor

Leader
Super Moderator
Yes,this is the best source for mechanical engineers; and I'm in your league,using it from 1964 (my first year in engineering college), gifted to me by my brother in law (12th edition-printed before my birth!!). Every one in the college use to envy me for this prized possession, and we always referred to it as 'BIBLE FOR ENGINEERS'. You have aroused a nostalgic feeling of the 'golden days'. :agree:

/Umang :thanks:

Umang,

For your information, the 28th Edition of the Machinery's Handbook has been announced.

Stijloor.
 
Last edited by a moderator:

Jim Wynne

Leader
Admin
It really depends on the application. If there is a problem with plating buildup, it's likely to be limited to the first couple of threads. Plating has a tendency to buildup in areas of high current density, and this includes the peaks of threads. In practical terms, plating rarely penetrates far enough into a hole to make a difference, and when it does, it usually means that the parts have spent too much time in the bath. As far as "G" and "H" designations go, those are metric thread classes, roughly analogous to designations such as "2B" in English threads. While they might be useful in preplate/post-plate situations, they are not intended for that purpose.

You are right Jim,and this exactly is what I have stated in my post.

2.I am unable to comprehend your last sentence,could you please throw light on intended purpose(s).

/Umang

The "G" and "H" designations represent tolerance classes, and aren't intended as pre- and post- plate sizes. Have a look at Thread Tolerancing for a good explanation.
 
Last edited by a moderator:
I

illinois_gage

Sometimes. In practical terms, plating rarely builds up enough inside threaded holes to make any difference in terms of corrosion protection anyway. Sometimes the purpose of plating is decorative or cosmetic and isn't intended to provide corrosion protection. This is often true of chrome plating on zinc castings.
Jim, when you see the chrome plating or zinc castings, is the quality still there on the product or does the plating / casting have a detriment to the product?
 

Jim Wynne

Leader
Admin
Jim, when you see the chrome plating or zinc castings, is the quality still there on the product or does the plating / casting have a detriment to the product?
I'm not sure that I understand the question, but if you're asking if chrome plating has a detrimental effect on zinc castings, you first have to define what "detrimental" means in this context. In other words, what are you concerned about, specifically? In general, properly specified and applied plating won't have a detrimental effect.
 
Top Bottom