# Calculating Plating/Coating Weight for IMDS

T

#### tomvehoski

Hello everyone. Have not been around here much lately...

I've run into a technical curiosity from my company's history that I though someone here might know about. I am now in the world of fastener manufacturing - primarily nuts and bolts - and we are required to submit to IMDS.

For calculating the weight of plating and coatings, most of our plants use Surface Area X Thickness X Density. At some point in the past, well before my time, we also published an internal IMDS guide along with training slides that used the following formulas:

Coating Weight of:

Bolt = .005 x Part Weight
Washer = .003 x Part Weight

Patch (Loctite, etc.) weight = .25 X Plating Weight

Using a fudge factor such as these is easier than calculating surface area, but I can't justify using them without knowing where the numbers came from - especially with the varying thicknesses and densities of coatings we use. Most of the documentation I have seen comes out of IMDS information, so I get the feeling these may have been generally accepted factors. It could also be someone pulled them out of thin air. The usage goes back at least eight years.

Has anyone seen factors like this used in the past and know of their source?

#### Jim Wynne

Staff member
Hello everyone. Have not been around here much lately...

I've run into a technical curiosity from my company's history that I though someone here might know about. I am now in the world of fastener manufacturing - primarily nuts and bolts - and we are required to submit to IMDS.

For calculating the weight of plating and coatings, most of our plants use Surface Area X Thickness X Density. At some point in the past, well before my time, we also published an internal IMDS guide along with training slides that used the following formulas:

Coating Weight of:

Bolt = .005 x Part Weight
Washer = .003 x Part Weight

Patch (Loctite, etc.) weight = .25 X Plating Weight

Using a fudge factor such as these is easier than calculating surface area, but I can't justify using them without knowing where the numbers came from - especially with the varying thicknesses and densities of coatings we use. Most of the documentation I have seen comes out of IMDS information, so I get the feeling these may have been generally accepted factors. It could also be someone pulled them out of thin air. The usage goes back at least eight years.

Has anyone seen factors like this used in the past and know of their source?
If you have a reliable scale, weigh 100 or so pieces (all at once) before and after coating. That should give you a reasonably accurate and empirical idea. If you do it with enough different items, you should be able to develop a reliable formula to use.

#### Ron Rompen

Trusted Information Resource
I have seen 'fudge factors' used in the past, particularly in the early days of IMDS, when it wasn't well understood by the people who were forced to come into immediate compliance with it. The thought process then seemed to be 'better close than nothing at all'.

In my personal experience, I have always done my best to accurately report the correct mass of all my coatings; not always an easy task, but cutting corners just isn't the right way to do things.

#### Kimmy

##### Involved In Discussions
I always weigh parts before and after plating but since most of our pieces come back from the plater weighing the same or less than they did before the plating, I wait until after they are plated to get a weight and then remove the plating with dilute hydrochloric acid aka muriatic acid for the before weight.

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