Metric Hardware and Plating

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Tom Scott
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Metric Hardware and Plating

#1 Post by Tom Scott »

I thought it might be interesting to prepare an elementary paper describing the above subjects, so here is my understanding of these. Constructive criticism is welcomed.

Metric Hardware
For Porsche Models 356 and 911
Tom Scott
This document is intended to provide a basic understanding of hardware which was used by Porsche when assembling the 356 and 911.
What is the purpose of the DIN number? It is a standardized numbering system which is intended to identify a particular item or thing, such as bolts, bolts, nuts screws and related hardware. There are virtually thousands of DIN numbers today, but this paper will be primarily concerned with those common to early Porsches.
In Europe, the most widely recognized organization responsible for establishing and publishing automotive standards is called Deutsches Institutfür Normung e.V. or abbreviated ‘DIN’. In this country, the Society of Automotive Engineers (SAE) is responsible for maintaining order by establishing many of the standards that apply to American automobile manufacturing.

It should be noted that the DIN numbered parts listed in the parts manuals are usually identified as a ‘900’-part number such as:
900-XXX-YYY-00 where the XXX can be decoded as the DIN number. There is a chart for these codes which I will attempt to re-create or acquire this. Furthermore, the first of the last two digits, 0 thru 7, describes the material used in the manufacturing, and the last digit describes the plating protection. These are: 0 – no corrosion protection; 1 – phosphate, Bostik and Endurion protection; 2 – galvanized coating; 3- varnish protection, and 4 – inkrom protection.
The third set of three numbers. YYY, is a unique identifier for the indivudual part.

The most common DIN Numbers – Nuts, Washers, Bolts, Screws and related hardware are:
84 Machine Screw, Cheese Head Slotted
85 Machine Screw, Fillister or Pan Head Slotted
86 Machine Screw, Oval Head Slotted
94 Cotter Pin
124 Rivet, Round Head
125 Flat Washer, Standard Size
127 Washer, Lock
137 Washer, Spring
603 Bolt, Carriage, Oval Head
660 Rivet, Round Head
912 Machine Screw, Allen Head
931 HEX Head Bolt, Partial Thread
933 Hex Head Bolt, Full Thread
934 Nut, Hex Head
935 Nut, Hex, Castle Head
936 Flat Washer, Medium Size
960 Hex Head Bolt, Partial Fine Thread
961 Hex Head Bolt, Full Fine Thread
963 Machine Screw, Flat Head Slotted
964 Machine Screw, Oval Head Slotted
965 Machine Screw, Flat Head Phillips
966 Machine Screw, Oval Head Phillips
6798 Washer, Lock, Serrated
6799 E Clip
6912 Machine Screw, Allen Head, Low Profile
7971 Sheet Metal Screw, Pan Head Slotted
7972 Sheet Metal Screw, Flat Head Slotted
7973 Sheet Metal Screw, Oval Head Slotted
7976 Sheet Metal Screw, Hex Head
7981 Sheet Metal Screw, Pan Head Phillips
7982 Sheet Metal Screw, Flat Head Phillips
7983 Sheet Metal Screw, Oval Head Phillips
7984 Machine Screw, Allen Head, Low Head
7985 Machine Screw, Pan Head Phillips
7989 Flat Washer, Fender
9021 Flat Washer, Fender
16159 Grommet, Rubber

There may be a suffix, either A or B attached at the end of the Din number and this
differentiates the slight variations of the part, i.e. Din 125 A, flat washer without chamfer and 125 B, flat washer with chamfer. Each hardware item is further defined by: size, both diameter and length; by type of material used to make the item; a code to identify the company which manufactured the item: the tensile strength, and the type plating applied.
The Size described in the Parts Manual will be: M**X**, such as M 8 X 25, the first ** defines the diameter of the shaft, 8 millimeters (mm) of a bolt or screw and the second ** defines the length, measured from the base of the head, as 25 mm in length. Some items do not have a length, such as washers and are described by the diameter only, M 8. Therefore, a hex head bolt, would be shown in the parts manual as: M 8 X 25 DIN 931.
A further complication with size was introduced when the hardware industry decided that the dimension across the head of bolts and nuts, or ‘across the flat’ (ATF), should be changed from 14 mm to 13 mm for 8 mm bolts. This transition was phased in beginning with the 356 B T6 model. The 14 mm ATF bolts and nut were used exclusively from 1950 until about 1962. However, 12 mm ATF 8 mm nuts were used in some tight areas such as for the carburetor intake manifold where the manifold is attached to the engine head and also where the carburetor attaches to the manifold. This variation may, or may not, be easily identified in the parts manual.
Next the code, or identification for each manufacturer of bolts only, is embossed on the head, such as NSF, KARRO, KMAX, VERBUS, etc. and the property class,( tensile strength) will also be embossed, usually 8.G (for early bolts and 8.8 later years) or 10.9.
Thread pitch for bolts and nuts are standard and not usually shown when referencing these. The standard thread pitch for various sizes is shown below:
Size Standard Fine Bolt Head Size
Pitch Pitch (Wrench Size)
M2 .4 4 mm
M3 .5 5.5 mm
M4 .7 7 mm
M5 .8 8 mm
M6 1.0 10 mm
M7 1.0 10 mm
M8 1,25 1.0 14 mm (1950-1963) , 13mm there after
M10 1.5 1.25 17 mm
M12 1.75 1.5 19 mm
M14 2.0 1.5 22mm
M16 2.0 1.5 24 mm

Type Material
The type material used may be shown in the parts book, such as:
St – Steel (usually a default and not shown)
Alu – Aluminum
Cu – Copper

Plating
Plating – various types of plating was used to protect the hardware item and to prevent corrosion. The processes for various plating methods is a very complex matter, however for our purposes these have been, hopefully, reduced to more simple terms.
The final, and most misunderstood, consideration is the types of plating used on each hardware item is usually shown in the parts manuals and may include the following.
(The following information was derived from a search on the 356 Talk discussions and other resources on the Internet.)
Zinc Plating
Verz. verzinkt, or verzenken in German, was one of the most common and inexpensive methods to protect steel, commonly described as ‘zinc’, or ‘St-verz’ in the parts manual. This process was a single stage and was not finished with a chromate wash, or conversion. This offered the least amount of corrosion protection and is often called ‘black oxide’. There was a second type of zinc plating, referred to as ‘gal Zn 9’ in the parts manual, or “black zinc” which was the standard zinc plating followed by a chromate conversion step which added additional plating and protection to the item.
Gal Zn 12 was a zinc plating process which produced a silver finish.
It is my opinion that, as a general rule, most 356 bolts and nuts were plated using a combination of black oxide or black zinc from Pre A up to the introduction of the T6 B model at which time silver zinc was used through the early 911 model, about 1965, when yellow zinc chromate was phased in. This was a plating method similar to black zinc but a yellow chromate conversion was applied following the initial step.
Phosphate
‘Phr E’ and ‘bost’ refer to Phosphate and Bostik-Endurion, an anti corrosive finish baked over phosphate – Bostik the manufacturer and Endurion the process. This type plating is identified as ‘phr E’ and was commonly used for all types of washers and some hex nuts. This process also produces a black finish, similar to black zinc. I cannot explain why the two types of plating, zinc and phosphate, were used, perhaps it was the manufacturer’s decision.
Cad or cadmium
Offered a better anti-seize and lubricating properties for nuts, bolts, screws, fuel lines and carburetor linkages. Cadmium is an electroplating process where cadmium is applied and then a supplementary coating is applied to produce a grayish silver color, commonly referred to as cad type 1, or Cad type 2 which has a yellow or gold finish.
Type I, ‘or referred to as clear cad’, results in a silver appearance and was used primarily for engine hardware for 356s from 1950 to 1961. The parts which were cad plated are usually identified in the description in the parts manual. The use of ‘clear cad’ on engine components varied by year and type of hardware and what each of these was is a topic for later discussion.
Type II yellow zinc chromate - results in a gold color was referred to as ‘Gelb Chromatiert’ in the 911 parts manuals.
Chrome
Verchr is used for many special parts such as head light rims, top latches, outside door handles, switch bezels, inside door handles, etc.
Nickel
Only a very limited number of parts were bright nickel plated. These were: Hazet wrenches, seat rails and screws for Pre A, A and B T5 models, Speedster seat hinge hardware, tool bag and tonneau cover buckles, keys and hood and engine release cable clamps
Anodize
Only a limited number of parts were anodized, another plating process. For the A model, the hood handle and some bumper guards, and the bumper and rocker trim for B and C models were anodized, This process is similar to chrome plating but produces a less shine to the finish.

What Is The Bottom Line To The Type Plating To be Used In A Restoration?
It seems impossible and unrealistic to attempt to re-plate hardware using the plating types specified for black plating in the parts manual. It is possible to plate hardware using black oxide or black zinc, however black oxide is not very durable and is prone to rust and corrosion unless the hardware is treated regularly, and often, with penetrating oil. Black zinc is much more durable and long lasting and is very similar in appearance. Attempting to re-plate the hardware using phosphate is likewise difficult and unreasonable. So, depending on your level of fanaticism, it might be acceptable to plate all parts identified as: zinc, gal zn9, bost., and phr E in the Pre A and A parts manuals using black zinc and achieve a reasonable, durable, maintenance free and acceptable appearance.
What do you think?
Dr. Nuts

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Mike Wilson
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Re: Metric Hardware and Plating

#2 Post by Mike Wilson »

In a word...AWESOME!

As far as replating black hardware, I've had parts plated with black chromate.
Mike Wilson
Lomita, CA
'63 B coupe

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Chuck House
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Re: Metric Hardware and Plating

#3 Post by Chuck House »

Tom wrote:
"A further complication with size was introduced when the hardware industry decided that the dimension across the head of bolts and nuts, or ‘across the flat’ (ATF), should be changed from 14 mm to 13 mm for 8 mm bolts. This transition was phased in beginning with the 356 B T6 model."

Really? I've seen 14mm bolts/nuts through the end of 356 production and even some on early 911s (valve cover nuts for example were originally 14mm ATF for '65 cars).
Chuck House
Southern California

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Ron LaDow
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Re: Metric Hardware and Plating

#4 Post by Ron LaDow »

Dr. Nuts (bolts, pins rivets, etc),
NICE work!
I don't know if you intended to park "Type II yellow zinc chromate" under "Type I, ‘or referred to as clear cad’", thereby sort of mixing Zn and Cd, but there it is.:
"Type II yellow zinc chromate - results in a gold color was referred to as ‘Gelb Chromatiert’ in the 911 parts manuals."
Every 'fresh' C caliper I've ever seen was yellow chromate; whether it was Zn or Cd, I really don't know. Given the heat calipers deal with, I'd *guess* the factory chose the more durable of the two; Cd.
And I'll agree with Chuck re: 14mm atf bolts and nuts; C engines use quite a few, including my 1965-build car.
Ron LaDow
www.precisionmatters.biz

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Re: Metric Hardware and Plating

#5 Post by Dave Erickson »

Tom,
very nice compilation of data. I have been doing a lot of reading about plating lately, the best source I am aware of being "Electroplating Fundamentals of Surface Finishing" by Frederick Lowenheim, and a more practical source being "Electroplating" by Mohler. I am working on setup of a plating work area where I can do alkaline zinc plating, chromate conversion, alkaline electrolytic de-rusting, phosphate dip and pickling, using 55 gal. and 33L Poly drums. I plan on plating fasteners, calipers, zamak castings (Solex carbs). This is a good retirement project for me; I have a degree in chemistry and worked as a water chemist during my early career, so its fun to relearn forgotten chemistry and apply it to something I love, 356's. I explain all this so that you won't think I have any expertise here, I am a student.

Lowenheim says that Zn plating is superior to Cd plating, thickness for thickness. The claims for Cd superiority came from the ratings from a test called the Neutral Salt Test, ASTM B117. If you live at the seashore or in areas where they use road salt, Cd plating will probably outlast Zn, but in long term service behavior, the neutral salt test is not a good predictor and it turns out that Zn outlasts Cd by a good margin.

One other bit of trivia: 356's used 12mm and 14mm ATF M8 fasteners, but not 13mm.

Also, the terms M8, M6 etc. by themselves refer to coarse pitch. If you want fine pitch you need to append it, e.g. M8x1.0. https://www.carrlane.com/catalog/index. ... 515F554A5B

Thanks for writing this paper, we really need this kind of information to be easily available.

-Dave

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Re: Metric Hardware and Plating

#6 Post by Bruce Smith »

I wrote an article on hardware plating for the magazine last year, Jan/Feb 2015. Covered a bit of the Porsche factory specs. for coating types as well. Here's a link to it:

http://www.sparkingplugs.com/resources/ ... lating.pdf

Also, Caswell and Brownells are a good source for supplies.

- Bruce
Last edited by Bruce Smith on Tue May 03, 2016 5:21 pm, edited 1 time in total.
Bruce Smith

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Re: Metric Hardware and Plating

#7 Post by Greg Bryan »

I did find a few 13 atf nuts and bolts when I did the hardware on my May 64 Cab.
Bolt - front hub to caliper
Nut for same
Bolt - front brake dust cover
nut - castle - steering coupler clamping bolt (bolt head is 14)
Greg Bryan

Edwin
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Re: Metric Hardware and Plating

#8 Post by Edwin »

Tom,
Fantastic start to document hardware.
Few comments, additions:
The DIN norms have changed over time. E.g. Modern Cheese heads look differently now compared the early ones, when did this change occur exactly?
M5's had 9ATF
Ph dipping gives a more grey-ish hue rather than black.
I believe the seat rails were chemically nickel dipped, not galvanic coated (Latter is softer)
How about the M10 14ATF Nut on early cars (Carbs to Manifold)
Sometime ago, I wrote about Din 137 wavy washers and regular washers. Their sizes were different (larger) in the day

Great stuff, thanks

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Re: Metric Hardware and Plating

#9 Post by Vic Skirmants »

Late Cs definitely had some 13mm hardware, specifically engine case perimeter bolts and transmission nose/intermediate plate through-bolts.

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Greg Bryan
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Re: Metric Hardware and Plating

#10 Post by Greg Bryan »

I've posted this list in the past, but seems germane to this topic. When I disassembled my car I carefully put every nut and bolt in a baggie and listed where it came from. Of course, when I had them plated, I had to throw them all together, so I made this spreadsheet.
On the list, I said they were black or zinc - I really don't know what material they were coated with, so this was a visual check only.
All nuts and bolts are from my May 64 Cab
There are a lot more nuts and bolts on the car, but this is a lot of them.
Porsche Nuts and Bolts (2).xls
(47.5 KiB) Downloaded 320 times
Greg Bryan

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Re: Metric Hardware and Plating

#11 Post by Mike Wilson »

Greg: in a word, EXCELLENT!
Mike Wilson
Lomita, CA
'63 B coupe

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Larry Coreth
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Re: Metric Hardware and Plating

#12 Post by Larry Coreth »

Greg,

Good info !! Your patience is exceeded only by your anal diligence and I love it .
Back in the day I made similar lists of parts on paper but the ability to sort and filter is a quantum leap forward.

Thank you !
Larry Coreth
Roanoake Rapids, NC

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Re: Metric Hardware and Plating

#13 Post by Spencer Harris »

Thanks Tom, Bruce & Greg!
Spencer Harris
San Joaquin Valley, CA.

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