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plating tolerance
3

plating tolerance

plating tolerance

(OP)
We typically specify zinc plating according to ASTM B633 including the thickness of the plating. We do not specify a tolerance for the thickness and I haven't been able to find anything that indicates what "standard" tolerances are for zinc electroplating.

Does anybody have any standards or experience with this you would be willing to share?

Thanks!!

RE: plating tolerance

If you are looking for calling out the plating tol on a dwg, I suggest leaving it off. Let the plater worry about the tol per the spec.
It depends on the type of plating and material.
A Google search shows a lot of data on this.
http://www.finishing.com/224/09.shtml

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

RE: plating tolerance

I think the Key here is finding a good plater.  I've had sloppy platers that leave parts in the solution until the edges smooth over.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
      o
  _`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right."  -- George Best

RE: plating tolerance

Here's an interesting link.  I have never used this plater but they have some good information on their website.

http://techplate.com/tpeprice.htm

RE: plating tolerance

ctopher

What would you do if you need to manufacture a plated 3A or 3B class thread on bolt or on tnternal thread? There is no way to do it without giving the thread tolerances before plating and after plating. The pre-plated tolerances dictate the desired plating tolerances. From my experience the tolerances for Zinc electorplating a tolerance of 0.003 to 0.0004 mm is common. For internal thread or holes an electrode inside the thread/hole may be necessary.

For example QQ-Z-325C federal standard dicatates 0.005 mm  for Class III and 0.013 for Class II. These are minimum plated thickness insure the 12/96 hours at salt spray bath. Therefore, you have to give tolerances to the plating if you manufacture parts such as class 3A and 3B bolts and threads.



 

RE: plating tolerance

I've rarely seen the thickness on a drawing, and if I recal when I did it was either on very old drawings or drawings that didn't reference an industry spec.  

However, I often see 'Dimensions apply after plating' as part of the plating note.


Probably not much help, sorry.

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

(OP)
The problem is that the ASTM B633 spec does not indicate a tolerance only 4 commonly used nominal thickness values. We specify a thickness because this effects salt spray resistance and the cost of plating. But how much is enough or to much?

We have some parts that have some tight tolerances so this can become very critical and chops away at the tolerances afforded to our manufacturing guys.

The link posted by ctopher seems to indicate to me that +/- .00015" on plating thickness is reasonable but I don't know if  this is actually easily produced using standard (i.e. low cost) plating methods.
 

RE: plating tolerance

We do not put plating thickness on mechanical drawings.  We use note "Dimensions apply after finishing".  Then our manufacturing engineers create what is called a processing drawing in which they account for finishing tolerances in the part creation.

Like I mention above.....find a good plater and talk with them about their process and ask good questions.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
      o
  _`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right."  -- George Best

RE: plating tolerance

I agree with Kenat using the 'Dimensions apply after plating' note. I have tried at various companies and designs using different types of plating, it can be very difficult to meet a thickness requirement indicated on a dwg. The tolerance you call out may work with one plater, but not another. Plating can be especially difficult to meet or inspect on threads.
Every company I have been with, the outcome was to leave off the tol on the dwg and call out the appropriate spec with type of plating.
I suggest calling your plater and ask them what their recommendation is.
My experience.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

RE: plating tolerance

Plating thickness is a function of the part geometry and topography, among other things.

There is no way to have a "standard variation" for plating thickness without also defining a standard test coupon.

I agree with the others that the finished part has its necessary tolerances defined by the part design engineer, and that the tolerances apply after plating.

A good plater will have a decent idea of what thickness variation to expect based on geometry and topography, and will work with you to suggest changes to the unplated part so that the finished part will be what you need.

A bad plater will feed you a line of BS about "standard plating thickness tolerances".

RE: plating tolerance

We also utilize a "Dimensions apply after finishing" note.  The main reason being the variability in processing as indicated by previous posters.  For highly toleranced parts, work to select a supplier and then help them develop the appropriate process controls for running your part.  For our more critical components, we have worked with the supplier (one who maintains excellent control on their bath chemistries) on racking locations and established standard lot sizes per run in addition to the more standard parameters such as masking locations.

Finding a good supplier and keeping communications going with them has proven beneficial to the results.  The trick then becomes keeping them from being cut out as a result of someone elses cost reduction efforts (unless the alternate source proves equally as capable)

Regards,

RE: plating tolerance

Asking for dimensions after plating is a "smart and hidden" way to ask for a tolerance on the plating thickness. The part before plating has its tolerances. The combined tolerances of the part and the platings gives the total tolerance. We do the same and give dimensions before and after plating but by doing so we actually dectate how to divide the tolerances between the machining and the plating.

RE: plating tolerance

For most applications I would have thought the 'dimensions apply after plating/finishing' is the better way of doing things from the designers point of view.  It leaves it up to the manufacturer to determine the pre treatment machined dimensions, dependant on their plating process.

For certain critical applications I suppose you may need more, is this what the OP is asking about?

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

My own preference, as an Engineer, on calling out plating thickness is that I never do it.  Platers know what they are doing with the part.  The machine shop is responsible to adjust their work to meet your final spec.  This is why I don't even use the instruction "Dimensions apply after finishing".  It is technically a process instruction in my mind, and process notes do not belong on drawings.  The part has to match the print when it comes in, period.  It's up to the vendor to make sure that happens by whatever means necessary (unless their is a case where process is important to the design, in which case, ASME covers those times with a special note).

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

RE: plating tolerance

fcsuper, I agree that process don't normally belong on the drawing per ASME standards.  

I don't see "Dimensions apply after plating/finishing" as being a process.  It's just a clarification of requirements.

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

The note "Dimensions apply after plating/finishing" is no less a process as any other note on a mechanical drawing.  If left to their own devices our inhouse machine shop would ignore notes.....it's our manufacturing engineers that develope process drawings that guide the machine shop.  They have all the information to make those adjustments to account for the finishing or plating.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
      o
  _`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right."  -- George Best

RE: plating tolerance

I don't see it as clarification as much as over stating what is already clear.  If the final part does not meet the specs on the drawing, then it is not to spec.  The one time I had a vendor not pay attention by not accounting for it, he called me before the plating process cuz he know his guy screwed up.  He tried to pull that argument with me but he backed down the instant he know he wasn't going to sell me snake oil that day.  The drawing shows the part in its final state.  This is per ASME.  State what you need.  How the shop gets there is up to them (under normal circumstances, of course).

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

RE: plating tolerance

(OP)
I have to spec out thickness because this ties into salt spray requirements. In addition, without some sort of thickness spec our manufacturing folks have no idea what thickness they need to account for in machining operations.

I would argue that without a thickness spec defined by design engineers and complete dimensional requirements for the final part how can the part be produced without someone making an assumption at some point? Granted the plating thickness is typically very small but can and has created problems for us.

All drawings do contain the note "dimensions and tolerances apply after plating or painting unless otherwise specified".

Of course I could be way off base here - wouldn't be the first time.

We manufacture most parts in house and send out for plating/painting when required. The only information on drawings are the final requirements and thickness of plating/painting so in process stuff is up to the manufacturing guys - they can do whatever so long as the end result meets spec.

RE: plating tolerance

In that case do you actually need to specify the tolerance or just the minimum plating thickness?

To meet the salt spray test maybe just specify minimum thickness.

I'm not familiar with ASTM B633 but I just looked at the UK defence standard we used to use in UK http://www.dstan.mod.uk/data/03/020/00000300.pdf and it actually says that you should specify the thickness of the plating on drawing (or in PO etc), so I was doing it wrong for a while.  However, it does only give minimum thickness where it talks about thickness for different applications, not a range/tolerance.

So I’d take a look at ASTM B633 and assuming it’s similar to the Def Stan I’d put a minimum plating thickness as required to meet whatever your salt spray test is.  I’d also still include the ‘dimension apply after plating’ note (sorry fcsuper, have to agree to disagree this time).

I’d still say it’s up to manufacturing to determine the actual machined dimensions/tols in coordination with the plating vendor but they would now have the minimum plating thickness as a start point.

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

The part should be designed based on the plating thickness. The engineer should know the spec.
Also, If you model the part, model it minus the plating for machining purposes. Some parts are machined after some plating. If the parts plating has to be precise for fit, make it a separate part to include plating, if needed.
Otherwise, create the part dwg, add the plating spec on the dwg. Some military programs require a similar note to the "dimensions and tolerances apply after plating or painting unless otherwise specified" note. It varies.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

RE: plating tolerance

Well, joebk, then I'd say it seems in your case there's need to call out the thickness. :)  Notice I didn't say not to call out a plating thickness...just that the note saying what the dims represent was unnecessary in most cases.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

RE: plating tolerance

Just for clarification, ASME Y14.5M-1994 Paragraph e states "The drawing should define a part without specifying manufacturing methods."  Paragraph f states "It is permissible to identify a nonmandatory certain processing dimensions that provide for finish allowance, shrink allowance, and other requirements, provided the final dimensions are given on the drawing.  Nonmandatory processing dimensions shall be identified by the appropriate note, such as "NONMANDATORY (MFG DATA)".  

Basically, the standard states that it is the processing dims that need identification, not the final dims; and that in either case the final dims have to be provided along with any included process dims.  

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

RE: plating tolerance

Fcsuper (and others), take a look at ASME Y14.5M-1994 Section 2.4.1 and see if it changes your mind.

2.4.1 Plated or Coated Parts.  Where a part is to be plated or coated, the drawing or referenced document shall specify whether the dimensions are before or after plating.  Typical examples of notes are the following:

(a)    DIMENSIONAL LIMITS APPLY AFTER PLATING.
(b)    DIMENSIONAL LIMITS APPLY BEFORE PLATING.
(For processes other than plating, substitute the appropriate term.)

I came across it by chance when looking for something else.

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

KENAT

"Typical examples of notes" meaning not mandatory. We can all do a flip flop as much as we like but every process has its tolerances. If a final dimension with a specified tolerance is needed there is no way to manufacture it without deciding how the tolerances for each process will be specified. We can try to hide it by throwing the burden on the plater but no plater in the world can make a plating with zero tolerance as no machining house can do a zero tolerance dimension. If for example the final outside diameter dimension or a part is 30 mm -0.010 mm and the minimum zinc coating is 0.005 mm, the part must be machined to 30 mm -0.001 to 0.002 to allow the zinc plater to reach the final dimensions unless he will plate, remove and re-plate over and over until he will (hopefully) succeed.

RE: plating tolerance

israelkk

Quote:

the drawing or referenced document SHALL specify whether the dimensions are before or after plating

The form of the note is not mandatory.  Having a note, or otherwise indicating when limits apply, apparently is mandatory as indicated by use of the work shall.  

As regards the rest of your post, I've previously written that depending on what the specific plating spec says it may be necessary to at least state a minimum required plating thickness.

I've also posted that I think it's probably best left to manufacturing to determine the divide in tolerance between plater & machine shop.  It could potentially vary between different platers so I'd probably leave it or ‘pre treatment’ dimensions off the drawings, although as fcsuper pointed out in a previous post ASME Y14.5 does allow for it to be on the drawing if required.

However, I didn’t put my previous post to restart the general debate, just to share information I’d found that states unequivocally (assuming you follow Y14.5) that an indication of whether dimensions apply before or after treatment is required.

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

Quote:

I've also posted that I think it's probably best left to manufacturing to determine the divide in tolerance between plater & machine shop.

Exactly what I said in my second post.  In most high end aerospace/defense companies their manufacturing engineers with the sole purpose of doing process drawings.  I don't think it's common in other industries.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
      o
  _`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right."  -- George Best

RE: plating tolerance

Inspecting a thread before and after plating that has special cutting can be a nightmare.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

RE: plating tolerance

If the thickness of the plating is not stated and can vary between suppliers, how exactly are the guys in the machine shop supposed to know what size to make anything before plating?

RE: plating tolerance

I have always designed the part for before plating. The plating spec calls out the thickness and tolerance.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

RE: plating tolerance

Quote:

If the thickness of the plating is not stated and can vary between suppliers, how exactly are the guys in the machine shop supposed to know what size to make anything before plating?
  A good manufacturing engineer that's creating process prints from a released CAD drawing will solve these types of problems.  This is nothing new here people

Heckler   americanflag
Sr. Mechanical Engineer
SWx 2007 SP 4.0 & Pro/E 2001
      o
  _`\(,_
(_)/ (_)

This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.

RE: plating tolerance

Sorry Heckler I have not come across this before, are you saying that the design and checking team create a component drawing that includes plating, and it then goes to a process engineer who creates a separate document for before plating?

RE: plating tolerance

If you need a plate to be .5" thick +/- .001 for some reason, and it is plated, powder coated, electropolished, or any other process that adds or takes away material - it is my feeling that you specify what you need in the END condition, and then the manufacturing engineer is there to figure out what the finished MACHINED part thickness is to account for the secondary processing.

Although now that I see it, I don't supposed specifying that the dimensions apply after all finishing processes is such a bad idea.

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

RE: plating tolerance

(OP)
I do not have the luxury of manufacturing engineers and our manufacturing folks either refuse to develop this information or aren't capable of doing so. If we don't spell out every detail for them the entire system grinds to a halt. Sucks but true.

To resolve the issue I need to include limits for the thickness of the plating so that our manufacturing folks can control their machining processes accordingly. I don't like this situation but I have little choice at this time.

I think my best option is to consult with a few plating vendors and specify a thickness range based on their recommendations and our corrosion resistance requirements and let the manufacturing guys sink or swim. I was hoping there was some sort of "industry standard" for this but apparently not.

Please note that I am not bashing manufacturing in general, just the chuckle heads I have to deal with.

Thanks for all of the feedback.

JBK

 

RE: plating tolerance

Another option is to have a machine dwg (before plating) and a plating dwg separate. This way the machinist does not have to worry about the plating, the plater does not worry about the machining. Just an option.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

RE: plating tolerance

I agree with ctopher. If there is no manufacturing engineer, then to make it easiest, have two drawings. Or maybe, sheet 1 and 2 (1 being machined condition, 2 being plated condition), with a note stating, "Send only sheet 2 to plating vendor."

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

RE: plating tolerance

The effect of coatings on threads is something to consider.  ASME B1.1 talks about it for UN threads.  If I recall correctly, then for class 1 or 2 threads by default the dimensions given in the standard actually apply before treatment.  The finish can take it upto class 3 (line fit).  The standard says a lot about this and I haven'rt looked in detail but I think this is more or less right.

ajack, while not normally a complete drawing I have seen it done that way.  The design team came up with the drawing for the finished item.  Manufacturing then determined any dimensions that needed to be made deliberately undersize etc and either came up with their own partial plan (drawing) or notes on a travelor or similar/equivalent.  It was definitely like this where I worked in the UK.

A lot of the time my guess is if the tolerance is say +-.005" while the plating is say less than .001" they don't really do anything except try and stay nearer the middle of the tol zone for the machining.

vc66, I personally hate the sheet 1 & sheet 2 being treated as almost separate drawings.  To me the possibility of confusing as to what state a part is at, either sheet 1 or 2 outweighs the advantages.  I've seen it cause problems.

What this thread and related threads/conversations etc has made me realize is just how important it is for the designers to know what the finishing spec says.  Some do define thickness, others give recomendations but seem to say that the drawing should state the thickness while if I recall correctly some perhaps don't even go that far.

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

I have often seen the finish note include the statement "DO NOT PLATE INDICATED HOLES", greatly simplifying the manufacturing engineers job ;)

RE: plating tolerance

joebk (Mechanical)

I would NOT leave a plating thickness spec off my part drawings. Doing so would leave yourself open to receiving out of spec parts from your plater. What are you going to gauge your parts to pre & post plating if the proper spec is not called out? That may come back to bit you later.

I recall the ANSI Standards book for threads calling out the proper method for calculating the new BEFORE PLATING sizes.

Hope this helps. There is also another thread in this forum dealing with plating callout on drawings.


RE: plating tolerance

You know, if we could come to agreement I'm pretty sure a FAQ on this would be a good ideawinky smile

The threads (no pun intended) on this subject really have reminded me just how important it is to know what the spec you call up says and what it says about how it should be called up on the drawing.  I also realize that it turns out that some of the information in my earlier posts was possibly wrong.

Some specs definitely do say that you should give the thickness, or at least the minimum thickness, on the drawing.

KENAT, probably the least qualified checker you'll ever meet...

RE: plating tolerance

I've compiled about as much as I could in the my extra time over the past week or so regarding plating in the attached updated excel file.  Though data is accurate, this should be treated as a tertiary reference, and not used for critical operations without checking the appropriate standards.  If there is missing information you can fill in or corrections necessary, please feel free to modify the file and attach to a posting on eng-tips in this forum.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

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