Hello Covers,

This is my first posting of a thread.

I am using 'GO' & 'NO GO' thread plug gages doing 100% inspection on the components.As per my knowledge,only half a thread of 'NO GO' gage is supposed to enter the component and a minimum of three threads are required to be on the gage.

My Sr. quality manager says nope,the limit of penetration of 'NO GO' gage is a minimum of half a thread,and maximum of one and a half thread.Does anyone has a written standard in support of the right assumption?:confused:

2.We are checking these components twice,once after the threading and again after zinc plating with the same gage!!My objections are over ruled by Sr.Q.Mgr. saying that this practice is going on without any serious problems.I have opined that different gages should be used,since the metal deposit after the plating reduces the ID of threads.May I have access to any standards on this,and more importantly what are the experts' opinion?

Thanking in anticipation.:o

Have a look at a similar thread: Thread Gage - No-Go end - No-Go end is allowed to enter the part up to 1.5 turns (http://elsmar.com/Forums/showthread.php?t=18515&highlight=plug+gage+standard)

Welcome Qualitytoughnut! I like the name. . .

Fastener threads are probably a little deeper a topic than you might expect. The application will determine how much engagement and the class of fits required on the mating threads as well as material, Heat Treatment and finish. In effect, how much static and dynamic loading the threaded joint will be required to withstand in what environment.

That being said. . . look into the ANSI/ASME standards such as ASME B1 series of standards for screw threads or the metric equivalents.

Typically, 1-1/2 turns MAX on the No-Go thread plug gage. There is no minimum specification that I am aware of. A lead-in countersink slightly over the major diameter of the female threads will aid assembly of the screw/bolt and will allow the No-Go to enter slightly.

Hope this helps a bit.

Hello Covers,

This is my first posting of a thread.

I am using 'GO' & 'NO GO' thread plug gages doing 100% inspection on the components.As per my knowledge,only half a thread of 'NO GO' gage is supposed to enter the component and a minimum of three threads are required to be on the gage.

My Sr. quality manager says nope,the limit of penetration of 'NO GO' gage is a minimum of half a thread,and maximum of one and a half thread.Does anyone has a written standard in support of the right assumption?:confused:

2.We are checking these components twice,once after the threading and again after zinc plating with the same gage!!My objections are over ruled by Sr.Q.Mgr. saying that this practice is going on without any serious problems.I have opined that different gages should be used,since the metal deposit after the plating reduces the ID of threads.May I have access to any standards on this,and more importantly what are the experts' opinion?

Thanking in anticipation.:o

Welcome on the cove and a "HAPPY NEW YEAR"

You are right about minimum 3 full threads on NO GO gages.The Machinery's Hand Book says (P 1201-1202) :"Not less than three full threads must remain on any NO GO plug".
It further adds:"No Go gages having 16 TPI or more are relieved on both ends 1/32" below the root of thread and 1/8" in from each end,the thread being removed."
Though it does'nt mention about the number of permitted turns for penetration,the relief at the end is provided to facilitate it's entry.

2.In addition to what 'The Taz' has said,can you be more specific about the kind of T.P.G. you are using viz:Taper lock,single plug,reversible or annular.Also what kind of component you are inspecting.

/Umang :bigwave:

The Machinery's Hand Book says (P 1201-1202) :"Not less than three full threads must remain on any NO GO plug".
It further adds:"No Go gages having 16 TPI or more are relieved on both ends 1/32" below the root of thread and 1/8" in from each end, the thread being removed."


Umang, thank you for referring to the "Machinery's Handbook (http://books.google.com/books?hl=en&id=u5Zo48XJ1EAC&dq=machinery's+handbook&printsec=frontcover&source=web&ots=WMRhQNAJ7E&sig=fjBPg7_SMaVJ1IVmHhX9yIA911M)."

This is a great resource that I have been using for over 40 years! Is gone through many revisions and updates. I recommend it highly.

Stijloor.

Welcome Qualitytoughnut! I like the name. . .

Fastener threads are probably a little deeper a topic than you might expect. The application will determine how much engagement and the class of fits required on the mating threads as well as material, Heat Treatment and finish. In effect, how much static and dynamic loading the threaded joint will be required to withstand in what environment.

That being said. . . look into the ANSI/ASME standards such as ASME B1 series of standards for screw threads or the metric equivalents.

Typically, 1-1/2 turns MAX on the No-Go thread plug gage. There is no minimum specification that I am aware of. A lead-in countersink slightly over the major diameter of the female threads will aid assembly of the screw/bolt and will allow the No-Go to enter slightly.

Hope this helps a bit.

Thanks for your advice.You as well Harry's link has indicated that my perception was incorrect,and my quality manager is right in allowing 1-1/2 turn penetration.

Please also guide my towards second part of my question.:thanks:


Welcome on the cove and a "HAPPY NEW YEAR"

You are right about minimum 3 full threads on NO GO gages.The Machinery's Hand Book says (P 1201-1202) :"Not less than three full threads must remain on any NO GO plug".
It further adds:"No Go gages having 16 TPI or more are relieved on both ends 1/32" below the root of thread and 1/8" in from each end,the thread being removed."
Though it does'nt mention about the number of permitted turns for penetration,the relief at the end is provided to facilitate it's entry.

2.In addition to what 'The Taz' has said,can you be more specific about the kind of T.P.G. you are using viz:Taper lock,single plug,reversible or annular.Also what kind of component you are inspecting.

/Umang :bigwave:

Thanks for the confirmation about a minimum of 3 threads on NO GO plug.The popular mis-interpretation of this is,that 3 threads are allowed to penetrate!!

2.I am using single plug,non reversible thread plug gages;having GO & NO GO on either end of single handle-from Baker,Size control & H.I.P.We are manufacturing Sealing-caps/Top-plate for spin-on filters,made from C.R and H.R sheets.

3.Is it appropiate to use same TPG after threading as well after zinc plating?Commonsense dictates nope,but can somebody provide authentic material on this. :frust:

3.Is it appropiate to use same TPG after threading as well after zinc plating?Commonsense dictates nope,but can somebody provide authentic material on this. :frust:

It depends on the amount of plating and the application. In some cases it is necessary to make allowance for plating, and custom "preplate" thread gages are used. There are some cases I've seen when a post-plating thread chasing operation is used because of the difficulty in predicting the size of the threads after plating.

There are some cases I've seen when a post-plating thread chasing operation is used because of the difficulty in predicting the size of the threads after plating.

Jim,

Would this "thread chasing" defeat the purpose of the plating process, namely corrosion resistance?

Stijloor.

Umang, thank you for referring to the "Machinery's Handbook (http://books.google.com/books?hl=en&id=u5Zo48XJ1EAC&dq=machinery's+handbook&printsec=frontcover&source=web&ots=WMRhQNAJ7E&sig=fjBPg7_SMaVJ1IVmHhX9yIA911M)."

This is a great resource that I have been using for over 40 years! Is gone through many revisions and updates. I recommend it highly.

Stijloor.

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:

Thanks for your advice.You as well Harry's link has indicated that my perception was incorrect,and my quality manager is right in allowing 1-1/2 turn penetration.

Please also guide my towards second part of my question.:thanks:




Thanks for the confirmation about a minimum of 3 threads on NO GO plug.The popular mis-interpretation of this is,that 3 threads are allowed to penetrate!!

2.I am using single plug,non reversible thread plug gages;having GO & NO GO on either end of single handle-from Baker,Size control & H.I.P.We are manufacturing Sealing-caps/Top-plate for spin-on filters,made from C.R and H.R sheets.

3.Is it appropiate to use same TPG after threading as well after zinc plating?Commonsense dictates nope,but can somebody provide authentic material on this. :frust:

You are welcome.Consult the Bible (Machinery's Handbook) often,to enlighten yourself.

2.You can get the right advice from Gage manufacturers;get it straight from the horse's mouth.

3.I am not current on the subject,but if my memory serves me right,there are G & H marks (followed by numericals)on the gages.I'm not sure but perhaps G is for production and H is for use after plating.The gage manufacturers may provide you with clarification,or some one here will guide you.

/Umang :bigwave:

Jim,

Would this "thread chasing" defeat the purpose of the plating process, namely corrosion resistance?

Stijloor.

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.

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

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.

[QUOTE=Jim Wynne;230114]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

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 (http://www.industrialpress.com/en/MachinerysHandbook/default.aspx?gclid=CISzuKeD4ZACFQGdPAodjVojWQ) has been announced.

Stijloor.

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 here (http://www.boltscience.com/pages/screw8.htm) for a good explanation.

The "G" and "H" designations represent tolerance classes, and aren't intended as pre- and post- plate sizes. Have a look here (http://www.boltscience.com/pages/screw8.htm) for a good explanation.

THANKS A LOT :D

/Umang