S30 Sheet Metal - Body and Chassis Panel Thicknesses

[dutchzcarguy]

For how to make your own metal part go to: Resources/knowledgebase/exterior.

[wheee!]

Here’s some pics:

 

Edited April 10, 2020 by wheee!

[Namerow]

Truly harrowing how such a thick piece of steel can be eaten through by rust.  I suppose it has to do with its location (up front and down low) and the moisture-retaining space created in the gap between it and the inner fender apron.  Maybe residual warmth from the engine after being parked helped out too.  There must have been a lot of salt-belt Z's that were just one pothole-in-the-middle-a-hard-corner away from having the front crossmember part company with the frame rails.  On a similar note, I remember back in the day hearing a story about a Z in Montreal that broke in half after a minor fender-bender ?

[Namerow]

On 4/6/2020 at 9:36 AM, grannyknot said:

But just as an aside, my American Standard Gauge gauge reads 20ga as .032", 19ga as .036", 18ga as .040", 17ga as .045", 16ga as .051 all of which are different from the table you posted

Sorry, I missed this earlier note from @grannyknot.  Wish I could remember where I got my gauge chart from (it dates back several years).  The discrepancy between GK's values and those from my chart are large, so I just went looking for another source and came up with this one from machinemfg.com (website for a machine manufacturer).  I wouldn't call it a definitive source, but the values coincide with the chart that I posted...

www.machinemfg.com/sheet-metal-gauge-sizes-chart-inch-mm/#Sheet_metal_GAUGE_thickness_chart 

So then I searched for a chart for the American Wire Gauge (AWG) and discovered that its values agree with GK's...

www.powerstream.com/Wire_Size.htm

None of my sources are definitive.  If someone wants to post the tables from an accepted engineering reference like Shigley's, that would resolve the issue once and for all (I never could afford that book when I was in school and just used my employer's copy after I got out into the workforce).

It appears, though, that we've tripped over yet another facet of wacky world of 'gauge' measurements  --  that is, that gauges have different 'thickness' values, depending on whether you're looking a wire diameter vs. sheet thickness.    Another vote in favor of metric.

Edited April 10, 2020 by Namerow
Link added

[Namerow]

New of my chart, updated with most recent contributions...

Panel Location	Measured Thickness (t)	Source	Gauge (derived from ‘t’)	Gauge (reported)	Source
Front Apron (engine compartment)	0.032”	Jfa.series1	20	20	Grannyknot
Tabco repair panels (all)				20	Manufacturer ConverTT
Klokkerholm repair panels (rear quarter)				22	ConverTT
Thick-gauge panels & pieces (which ones?)				18	2manyZs kmack
Lower Front Frame Rail (OE)	0.050”	Carl Beck	18	18	ConverTT
Lower Front Frame Rail (ZeddFindings)	0.062”	Namerow	16
Lower Front Frame Rail - Reinforcement plate (‘pocket’) at front crossmember mounting point	0.0747	AZStory	14
Upper Front Frame Rail (‘horn’)	0.054”	Carl Beck	~ 16
Front Valence Panel	0.032”	Namerow	~ 20
Front Crossmember	0.076”	Namerow	~ 14
Door – outer skin				20	ConverTT
Inner Rocker Panel				18	ConverTT
Radiator Support				18 + 20	ConverTT
Floor Pan (OE)	0.044”	CanTechZ	~ 18
Floor Pan (ZCar Depot)	0.045”	vendor	~ 18
Floor Pan Bottom Rail (ZCar Depot)	0.060”	vendor	16

[dutchzcarguy]

17 hours ago, Namerow said:

we've tripped over yet another facet of wacky world of 'gauge' measurements  --  that is, that gauges have different 'thickness' values, depending on whether you're looking a wire diameter vs. sheet thickness.    Another vote in favor of metric.

It's like the (english) imperial gallon (4,546 Liter.)  and the (american) US Gallon ( about 3,785 liter.) all over!!

1 Imperial gallon = 1.20095042 US gallon = 4.54609188 Liters

And when someone starts talking about Pints, ? i always have to laugh about it, yeah do me a Pint.. 

[Namerow]

Not that the metric system doesn't have its own moments.  Consider the standard for determining the metre length unit. 

The basic unit of length in the metric system; it was originally planned so that the circumference of the Earth would be measured at about forty million meters. A meter is 39.37 inches. Today, the meter is defined to be the distance light travels in 1 / 299,792,458 seconds.

Based in science? Yes.  Intuitive?  Not hardly.  I like the definition of the kilogram better:

The kilogram is almost exactly the mass of one litre of water.

Consider, by contrast, the definition of the inch:

The old English ynce was defined by King David I of Scotland about 1150 as the breadth of a man’s thumb at the base of the nail. To help maintain consistency of the unit, the measure was usually achieved by adding the thumb breadth of three men—one small, one medium, and one large—and then dividing the figure by three. During the reign of King Edward II, in the early 14th century, the inch was defined as “three grains of barley, dry and round, placed end to end lengthwise.” At various times the inch has also been defined as the combined lengths of 12 poppyseeds. 

Makes one pause when considering the implications of having a 427 cubic inch engine in your car.?

[AZStory]

On 4/10/2020 at 10:11 AM, Namerow said:

New of my chart, updated with most recent contributions...

Panel Location	Measured Thickness (t)	Source	Gauge (derived from ‘t’)	Gauge (reported)	Source
Front Apron (engine compartment)	0.032”	Jfa.series1	20	20	Grannyknot
Tabco repair panels (all)				20	Manufacturer ConverTT
Klokkerholm repair panels (rear quarter)				22	ConverTT
Thick-gauge panels & pieces (which ones?)				18	2manyZs kmack
Lower Front Frame Rail (OE)	0.050”	Carl Beck	18	18	ConverTT
Lower Front Frame Rail (ZeddFindings)	0.062”	Namerow	16
Lower Front Frame Rail - Reinforcement plate (‘pocket’) at front crossmember mounting point	0.0747	AZStory	14
Upper Front Frame Rail (‘horn’)	0.054”	Carl Beck	~ 16
Front Valence Panel	0.032”	Namerow	~ 20
Front Crossmember	0.076”	Namerow	~ 14
Door – outer skin				20	ConverTT
Inner Rocker Panel				18	ConverTT
Radiator Support				18 + 20	ConverTT
Floor Pan (OE)	0.044”	CanTechZ	~ 18
Floor Pan (ZCar Depot)	0.045”	vendor	~ 18
Floor Pan Bottom Rail (ZCar Depot)	0.060”	vendor	16

I'd just like to clarify that in my photo, my thickness gauge would not clear the sheetmetal on the "pocket" piece at 14g.  I think it's 12g sheetmetal. 

Edited April 12, 2020 by AZStory

[Namerow]

7 hours ago, AZStory said:

I'd just like to clarify that in my photo, my thickness gauge would not clear the sheetmetal on the "pocket" piece at 14g.  I think it's 12g sheetmetal. 

Point noted.  However, 14-gauge sheet can be anywhere from 0.0697" to 0.0797" so your measuring gauge (sized at the median thickness of 0.0747") could register a 'no-go' even though the piece actually was made from "14-gauge" steel.

More likely, however, is that this piece (like most of the other steel used in the S30)  was made from sheet steel rolled to the metric standard by a Japanese steel mill.  It seems very like that this doubler/reinforcement piece was stamped from 2.0mm stock (which nominally converts to 0.079" and would therefore likely register as 'too thick' for your measurement gauge's '14-gge/0.0747"' slot).

Note also that 12-gauge is a big jump up in thickness from 14-gauge...  0.1046" vs. 0.0747", so an increase of 0.0299"... which is almost 1/32".  From your picture, it doesn't look like your there's a mismatch of 0.03" between the S30 part and the 14-gge slot in your measurement gauge.  It also looks like your 12-gauge slot would be way too big...

All things considered, then, I like "14-gauge" for this part because it's very close* to what is most likely the real truth -- which I think is 2.0mm.
(* 2.0mm/0.0787" vs. 14-gge/0.0747", so within 5% using the nominal design thicknesses).

My purpose in starting this thread was to create a reference chart for selecting the right** sheet thickness to use for panel repairs.  Since very few of us (in Canada and the US) have convenient access to metric-standard sheet steel, the best guidance for repair panel thickness comes in the form of 'gauge'.  I suppose I could add a "mm" column, but that would confuse the heck out of everyone.
(**  Let me qualify my use of the word 'right' by adding that there's sometimes an incentive for using a thicker steel than the factory did.  A good and common example is the bottom rail ('support') for the floor pans, where some owners choose to go with a thicker-than-factory steel and go full-length in an effort to better tie the front and rear sections of the 'chassis' rails together.)

Edited April 12, 2020 by Namerow
new comment added

[Namerow]

Table updated to show revised (refined) measurement for the lower front frame rail reinforcement piece...

Panel Location	Measured Thickness (t)	Source	Gauge (derived from ‘t’)	Gauge (reported)	Source
Front Apron (engine compartment)	0.032”	Jfa.series1	20	20	Grannyknot
Tabco repair panels (all)				20	Manufacturer ConverTT
Klokkerholm repair panels (rear quarter)				22	ConverTT
Thick-gauge panels & pieces (which ones?)				18	2manyZs kmack
Lower Front Frame Rail (OE)	0.050”	Carl Beck	18	18	ConverTT
Lower Front Frame Rail (ZeddFindings)	0.062”	Namerow	16
Lower Front Frame Rail - Reinforcement plate (‘pocket’) at front crossmember mounting point	0.0787” (2.0mm)	AZStory	~ 14
Upper Front Frame Rail (‘horn’)	0.054”	Carl Beck	~ 16
Front Valence Panel	0.032”	Namerow	~ 20
Front Crossmember	0.076”	Namerow	~ 14
Door – outer skin				20	ConverTT
Inner Rocker Panel				18	ConverTT
Radiator Support				18 + 20	ConverTT
Floor Pan (OE)	0.044”	CanTechZ	~ 18
Floor Pan (ZCar Depot)	0.045”	vendor	~ 18
Floor Pan Bottom Rail (ZCar Depot)	0.060”	vendor	16

[CanTechZ]

This morning I re-measured my floor pan thickness with seats out and better light, the new reading was .040" (1.02mm). However with the better light I noticed that there was still original paint on the under side that was quite thick. After scraping off some paint I measured again and the new reading was .0315" which equals .800mm. My car is a 7-70 production date.

[CanTechZ]

Here is another floor pan measurement, this time for the mid floor section behind the left seat. Measured .030" (.76mm). Most likely 0.8mm thick sheet metal. Again about the only good purpose for a rust hole.