Thickness

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Author Message (Unregistered Guest) Unregistered guest Posted on Friday, April 25, 2008 - 04:08 pm:    Do you use USS gage numbers or minimum thickness when specifying sheet metal items? Are you aware of and using the thoughts from ASTM A480/A480M? Do you vary this information in different types of uses? Thanks Richard Howard, AIA CSI CCS LEED-AP Senior Member Username: rick_howard Post Number: 174 Registered: 07-2003 Posted on Friday, April 25, 2008 - 05:12 pm:    Thicknesses are required if you want to have anything specific to hang your hat on. US gages are ambiguous; the standard defining them was withdrawn ages ago. I still have certain items, like HM doors and frames or metal roofing and siding, where I invariably get asked what gage I want. I always bump it up at least one size heavier in my answer just to tweak them. Then they reply that the thickness I called out is something else and I tell them to just make sure it meets the minimum thickness called out in the spec. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 40 Registered: 01-2008 Posted on Friday, April 25, 2008 - 05:13 pm:    Prior to 1970, sheet steel was referred to by gage. ASTM and ANSI currently do not list gage numbers in their standards. Like many generic terms, gage (or gauge) is ingrained in many vocabularies and is misunderstood as a term for thickness. NAAMM has published a minimum thickness table to be used instead of discontinued gage numbers. The values used by NAAM were taken from the Underwriters Laboratories, Inc. publication for gage number and equivalent thickness. I use the NAAM table for ticknesses in decimals of an inch. Steel stud thickness (exlcusive of coating) are now given in mils as published by SSMA. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 41 Registered: 01-2008 Posted on Friday, April 25, 2008 - 05:15 pm:    I mean "thickness" not "tickness" Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 762 Registered: 07-2002 Posted on Friday, April 25, 2008 - 05:24 pm:    I agree with Richard for this. if you look at the SMACNA manual, you'll see that even the same "gage" for varying metals varies in thickness (ie, 24 gage stainless is a different thickness than 24 gage sheet steel); and some metals, such as aluminum, don't come in gages anyway. for items that are commonly referred to using gage measurements (such as hollow metal doors and frames) I insert a table in my product sections that defines what thickness is comparable to what gage for that section. I also define that the thickness is the base metal - not the metal with galvanizing or other coating on it. My project people still think in "gage" thickness, so I provide the table as a translation tool for them as much as anything. Ralph Liebing, RA, CSI Senior Member Username: rliebing Post Number: 832 Registered: 02-2003 Posted on Monday, April 28, 2008 - 07:29 am:    Great information. We just had the same conversation in our office. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 888 Registered: 03-2002 Posted on Monday, April 28, 2008 - 08:14 am:    For the steel stud industry, I found three different thicknesses that are all "20 ga." Illustrates how useless it is. I have started to use "mil thickness" designations for steel studs. It is a shorter nomenclature than decimal inches. Thus, a 0.0312-inch stud becomes 30 mil. To answer the question more generally, I never specify using gauge. Steven Bruneel, AIA, CSI-CDT, LEED-AP Senior Member Username: redseca2 Post Number: 102 Registered: 12-2006 Posted on Monday, April 28, 2008 - 12:06 pm:    I agree with Anne's comment. As it seems impossible to eliminate the use of the term "gage" in day-to-day job-site conversation and communication, we often add a chart to a "Definitions" article that provides a minimum inch thickness to "gage" translation. Christopher E. Grimm, CSI, CCS, LEEDŽ-AP, MAI, RLA Senior Member Username: tsugaguy Post Number: 143 Registered: 06-2005 Posted on Monday, April 28, 2008 - 09:16 pm:    What reference standard is there that gives gages and corresponding thicknesses WITH tolerances for a wide range of architectural sheet metals? SMACNA leaves several important types out that are used for metal roofing, and if I remember right it doesn't have tolerance ranges. The ASTM standard has tolerances but also is lacking some types of sheet metal. We are thinking of developing a table, not sure which one to use as a starting point, maybe will combine from multiple sources and choose between them where there are conflicts. I am starting to paste tables into the spec for other fuzzy issues, like conc floor flatness and leveling (which seems to always require us looking the values up so we can spec them - why not have a table in our master and delete the ones we don't need - also helps address leveling on elevated slabs), and paint gloss standards (manufacturers differ, MPI helps in part, but putting the table in the spec and saying 60 degree is what we are using and here is how you convert begins to help). So far people really seem to like the extra clarity, and it helps me out too. Still no way to make people read the spec when they are content to read the gage and move on. Christopher E. Grimm, CSI, CCS, LEEDŽ-AP, MAI, RLA Senior Member Username: tsugaguy Post Number: 144 Registered: 06-2005 Posted on Monday, April 28, 2008 - 09:19 pm:    ASTM has tolerances for various nominal thicknesses, that is.