Sheet Metal

Layout

• Sheet Metal: Gauges, Materials, Tools

  Gauge numbers run backwards and are material-specific, so this is where you learn to read a thickness before you cut one. Covers the common sheet materials, the shop machines that cut, bend and roll them, and the guarding rules that keep your fingers.

• Pattern Development and Layout

  Turning a three-dimensional fitting into a flat pattern you can cut. Parallel line, radial line and triangulation are the three methods, and knowing which one a shape calls for is most of the skill.

• Fabricating Fittings and Transitions

  Elbows, offsets, tees and square-to-round transitions, laid out and formed. The fittings are where a duct system gains most of its pressure loss, so geometry here is not cosmetic.

• Seams and Connections

  Pittsburgh locks, standing seams, drive cleats and S-slips are different joint families with different jobs. Which one belongs on a given duct is a construction-standard question, not a preference.

Safety

• Sheet Metal Hazards: Machines, Edges, Fumes, Heights

  The four ways this trade hurts people, and the OSHA pages that govern each. Shears and press brakes are machine-guarding hazards, cut sheet is a laceration hazard, welding and brazing carry fume and radiation exposure, and duct hanging is work at height.

Installation

• Duct Construction Standards (SMACNA)

  SMACNA's HVAC Duct Construction Standards, Metal and Flexible, now in its 4th edition, is the document that decides metal thickness, reinforcement, assembly and supports. SMACNA is accredited by ANSI as a standards developer, so this is a consensus standard, not a manufacturer's recommendation.

• Duct Installation and Support

  Hanging and supporting duct so it stays where you put it, and doing it off the ground safely. Support spacing and hanger selection come out of the construction standard; the fall protection comes out of OSHA.

• Duct Sealing and Leakage Testing

  Sealing is what you do to the joints; leakage class is what the finished system is measured against. SMACNA publishes the testing side separately as an American National Standard, ANSI/SMACNA 016-2012, which is a hint that the two are not one topic.

Tab

• TAB Fundamentals

  Testing, adjusting and balancing is three distinct verbs, not one. TAB verifies, tests and adjusts an HVAC system after installation or retrofit so every terminal gets its design share of the air.

• Airflow Measurement Instruments

  Manometers, pitot tubes, hoods and anemometers, and what each one actually reads. Static, velocity and total pressure are three different quantities, and a traverse measures velocity to infer volume.

• Balancing Procedures

  Proportional balancing, from setting the fan to trimming the last diffuser, and writing the report that a certified supervisor or professional signs. AABC requires technicians to be competent in both air and water balancing.

• TAB Certification (TABB, NEBB, AABC)

  Three separate bodies certify the same discipline and none of them recognise each other's cards. This is the map: what TABB, NEBB and AABC each certify, the two-tier ladder inside each, and why the right answer often depends on who employs you.

• TAB and Commissioning Are Not the Same Scope

  TAB measures and sets the systems; commissioning independently verifies that they meet the owner's requirements. The confusion is understandable because the same bodies certify both, with NEBB running separate TAB and Cx disciplines and ICB listing a TABB Commissioning Supervisor alongside the TABB Technician.

• Firm Certification vs Individual Certification

  A spec calling for a certified TAB firm is not satisfied by one employee holding a card, and the reverse is also true. NEBB certifies firms and people separately, AABC approves member agencies and certifies individuals inside them, and ICB/TABB is a personnel certification body.

• TABB Certification: Technician and Supervisor

  The TAB certification issued through the International Certification Board, which states it is accredited to ISO/IEC 17024 by ANAB. The technician route is a written exam plus an 8-hour hands-on practical in a certified TABB lab; supervisors qualify and sit their own exam and then review technicians' reports.

• NEBB Certification: Certified Technician and Certified Professional

  NEBB certifies both firms and people, across eight disciplines of which TAB is one. Certified Technicians work under the guidance of a Certified Professional, and only Certified Professionals working for certified firms may authenticate official reports.

• AABC Certification: TBT and TBE

  AABC certifies the Test and Balance Technician at three years' experience and the Test and Balance Engineer at eight, the latter through an 8-hour written exam. The catch that shapes careers: AABC individual certification is open only to employees of approved AABC member companies.

Standards

• Which SMACNA Standard Governs What

  SMACNA publishes a shelf of separate standards and picking the wrong one wastes a day. Construction, leakage testing, fibrous glass, seismic restraint and residential each have their own document, and SMACNA is an ANSI-accredited standards developer rather than a code body or a certifier of people.

• Pressure Class, Seal Class and Leakage Class

  Three separate selections that get collapsed into one idea constantly. Pressure class drives thickness and reinforcement, seal class says what gets sealed, leakage class is what the finished duct is measured against, and you choose them independently.

• Running a Duct Leakage Test

  How a duct leakage test is actually set up and run, and how it differs from a blower-door test on the building envelope. SMACNA's HVAC Air Duct Leakage Test Manual, ANSI/SMACNA 016-2012, covers the test procedures, the apparatus and the analysis.

• The Sheet Metal Apprenticeship (SMART/ITI)

  A four or five year earn-while-you-learn apprenticeship with a high school diploma or GED as the entry requirement. Training runs through local Joint Apprenticeship Training Committees using a standardised curriculum from the ITI, which SMART and SMACNA jointly sponsor.

• Becoming a Sheet Metal Contractor

  Going from holding a card to running the company. Sheet metal work mostly rides on mechanical or HVAC contractor licensing at state level, and in the TAB market the firm itself may need to be certified, which is a separate thing from your own certification.

• Moving From Installer to TAB Technician

  TAB is the trade's genuine non-entry specialisation, and it is reached from the tools rather than instead of them. What the move involves, which of the three certifying bodies your employer points you at, and why that choice is usually made for you.