Glass Master® Duct Board Grooving Machines are the ultimate solution for HVAC professionals looking to streamline their duct fabrication process. As the world leader in duct board grooving machines, Glass Master sets the standard for speed, accuracy, and reliability on commercial and residential jobs of any size.
With these industry-leading machines, contractors can drastically increase productivity while achieving clean grooves. The result? Precise fabrication, reduced material waste, and faster installations.
What Can Glass Master Machines Do?
Engineered for high-volume operations, Glass Master machines make it fast and easy to create clean and consistent rectangular and spiral ductwork grooves. Both the Glass Master SG-220 and Glass Master SG-420 use precision-ground cutting blades and electric motor-powered drive rollers to groove virtually any rectangular 1-inch, 1.5-inch, or 2-inch fiberglass duct board. And the SG-420 can groove boards to create both rectangular and spiral duct liner.

Setting Up Your Glass Master Machine
The initial set up of your machine can be done in roughly four steps. Review the set-up video and consult your machine guide for thorough instructions that include important details not listed below.
- Using a forklift, lift the machine 10 inches and fasten casters in place.
- Place the foot switch in your desired position on the floor.
- Plug the machine into a 120-volt, 15-amp or higher power outlet.
Load cutting tools A, B, C, D, and E into the machine in alphabetical order.

Setting the Machine Blades
Proper blade adjustment is essential to achieving clean, precise grooves. For Tool A, which removes fiberglass from the foil surface to create a staple flap on the left-hand edge, set the blade height so a sheet of paper or thin metal slides between the blade and roller. A clean staple flap with little to no fiberglass on the foil scrim indicates correct adjustment. If fiberglass remains, the blade is too high; if the foil tears, it’s too low.
Tools B, C, D, and E each use two blades to create modified shiplap cuts on the remaining three corners. Start by setting the single-bend blade using the same paper test method, then match the three-bend blade to it. Test and adjust as needed for accuracy.

Adjusting for Board Thickness
Select the appropriate tools for each thickness of board. The arrows on each end of the machine serve as a guide for the approximate gap settings for different board sizes. A quick check of the gauge confirms you’re correctly set.
The roller gap can be increased or decreased by turning the adjustment screw at both ends of the machine. Always adjust in small increments to maintain even spacing and prevent stress on the roller bearings. Once the gap is properly set and the correct tool holders are installed, the machine is ready to groove your selected board thickness.

Machine Care and Maintenance
To keep your machine running smoothly, follow best maintenance practices and use only original replacement parts. The cutting blades, made from factory-hardened spring steel, offer long-term wear resistance but will eventually dull from use. Sharpening blades is not recommended, as it can weaken the metal. Instead, refer to the manual for blade replacement and adjustment procedures.
Routinely inspect the drive system as fiberglass may wear down the non-skid coating of the roller wrap on the top drive rollers. Order replacement materials and adhesive if needed. Periodically remove both end covers to check the drive chain tension and sprockets for alignment and wear. Realign and securely tighten any loose sprockets and clear away fiberglass buildup. Avoid lubricants, as they attract fibers and accelerate wear.

Helpful Tips for Reliable Performance
A challenge you may encounter with your Glass Master machine is pulling or tearing of the glass fibers or facing material. To resolve this, inspect the cutting blades for any buildup or wear and clean them thoroughly or replace them if needed. Also check the duct board itself for defects like uneven binder distribution or improper curing. Finally, verify blade settings and adjust them according to the manual.
If the board doesn’t feed squarely or twists during operation, make sure you’re following the correct feeding procedure, confirm the drive roller gaps are evenly set for the board’s thickness, and check for worn top drive rollers. Misaligned or worn blades can also contribute to this issue. If the drive rollers won’t turn, check that power is connected and inspect the foot switch for proper function.
These steps can solve most issues and keep your machine running efficiently. For more help, refer to the operator’s manual or contact CertainTeed Machine Works directly at cmw@saint-gobain.com and 1-800-237-7841.

Your Complete Source for Ductwork Fabrication
Glass Master machines and FabMaster Duct Board Grooving Hand Tools work together with CertainTeed UltraDuct® Black Duct Board to deliver a complete, integrated system. This system enables HVAC professionals to simplify and streamline procurement with a one-stop-shop for all ductwork fabrication needs. It also ensures that all components are compatible and gives contractors a single source for expert technical service and support.
Part of the comprehensive CertainTeed Machine Works portfolio, Glass Master machines are known for exceptional durability and easy maintenance. Their longevity is supported by the Machine Works inventory of spare parts, available to order online. Machine Works also offers American-made insulation blowing machines, vacuums, fireproofing machines, and more.
Learn more about the advantages of Glass Master and other Machine Works solutions at CertainTeed.com/Why-Machine-Works.