Machinery's Handbook, 31st Edition
Sheet Metal Joints
1445
Groove Seam:
The groove seam (Fig. 40) is often used for rectangular or round duct straight joints, or to join some sheets for fittings that are too large to be cut out from standard sheets. It is also known as the pipelock, or flat lock seam.
Fig. 40. Groove Seam Corner Standing Seam:
The corner standing seam (Fig. 41) has applications similar to the standing seam, and also can be used for straight-duct sections. This type of seam is mostly applied at the ends at 8 inches (203 mm) intervals.
Fig. 41. Corner Standing Seam
Double Seam:
The double corner seam (Fig. 42) at one time was the most commonly used method for duct fabrication. However, although it is seldom used because of the hand operations required for assembly, the double seam can be used advantageously for duct fittings with compound curves. It is called the slide lock seam. Machines are available to automatically close this seam. The slide-corner (Fig. 43) is a large version of the double seam. It is often used for field assembly of straight joints, such as in an existing ceiling space, or other restricted working area where ducts must be built in place. To assemble the duct segments, opposite ends of each seam are merely “entered” and then pushed into position. Ducts are sent to job sites “knocked- down” for more efficient use of shipping space. The button punch snap lock (Fig. 44 ) is a flush-type seam that may be soldered or caulked. This seam can be modified slightly for use as a “snap lock”. This type of seam is not applicable for aluminum or other soft metals. This seam may be used up to 4” (10.2 cm) w.g. by using screws at the ends. The pocket depth should not be smaller than 5 ∕ 8 inch (15.88 mm) for 20-, 22- and 26-gage material (0.91- 0.45 mm).
Fig. 42. Double Corner Seam
Slide-Corner:
Fig. 43. Slide Corner
Button Punch Snap Lock:
Fig. 44. Button Punch Snap Lock
Pittsburg:
The Pittsburgh (Fig. 45) is the most commonly used seam for standard-gage duct construction. The common pocket depths are 5 ∕ 16 inch (7.94 mm) and 5 ∕ 8 inch (15.88 mm) depending on the thickness of the sheet.
Fig. 45. Pittsburgh
Flange:
The flange (Fig. 46) is an end edge stiffener. The drafter must indicate size of flange, direction of bend, degree of bend (if other than 90 ° ) and when full corners are desired. Full corners are generally advisable for collar connections to concrete or masonry wall openings at louvers.
Fig. 46. Flange
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online