Actions

Knocked Up Joint

From DT Online

Description

A Knocked Up Joint or Double Seam is commonly used to fix an end to a cannister or food can. The canning industry would normally use a Seaming Machine (see A Dash of Science for further detail) but they were traditionally hand made by Tinsmiths. If made properly a Knocked Up Joint should be water-tight without being soldered but, of course, they can be soldered as well if required.


Making the Joint
TinsmithMakingStandingSeam.png
  • To make the base, mark out a circle with its radius equal to the cylinder radius plus twice the width of the Seam.
  • Form a rim round its outside with a depth equal to the width of the Seam (do this by working around the circumference little by little with Flat Nosed Pliers and truing up with a Boxwood or Rawhide Mallet on a Mandrel Stake).
  • The length of the cannister needs to be extended by the width of the Seam so that a flange equal to this can be formed around one end (as before, do this by working around the end little by little with Flat Nosed Pliers and truing up with a Boxwood or Rawhide Mallet on a Bench Block, Tinman's Anvil or similar flat surface).


TinsmithMakingKnockedUpJoint.png
  • Place the flanged cannister inside the rim of the base and flatten the rim down on to it using a Boxwood or Rawhide Mallet down on to a Bench Block or similar surface.
  • The joint formed at this stage is known as a Paned Down Seam
  • To complete the Knocked Up Joint or Double Seam, the cannister is held on to a Mandrel Stake and folded over again as shown.

Note: Use a Mallet and not a Hammer to avoid stretching the metal as it is struck (this would cause the edge to distort).



DT Online Buyers' Guide
Thor 114 Rawhide Mallet Size 3 Emir 86 Tinsmans Mallet 50mm Kreator Professional Quality Graphite Shaft Machinist Hammer 300g KRT901201 Gilbow G69 Right Hand Universal Tin Snip 11-inch Gilbow G67 Left Hand Universal Tin Snip 11-inch CLARKE METALWORK METAL FOLDER BENCH/VICE MOUNTED PANEL FLANGING / JOGGLER & 5mm HOLE PUNCH TOOL Extra Large Solid Steel Bench Block 6 Draper 35481 4.5KG Anvil Single Bick (Cast Iron) CLARKE SPOT WELDER 230v 13Kw MILD STEEL 2mm + 2mm CSW13T
Thor 114 Rawhide Mallet Size 3 Emir 86 Tinsmans Mallet 50mm Fiberglass Shaft Machinist Hammer 300g KRT901201 Gilbow G69 Right Hand Universal Tin Snip 11inch Gilbow G67 Left Hand Universal Tin Snip 11inch Bench/Vice Mounted Sheet Folder Panel Flanging/Joggler Tool with 5mm Hole Punch Extra Large Solid Steel Bench Block 6" x 4" x 3/4" Draper 35481 4.5KG Anvil Single Bick (Cast Iron) Clarke Spot Welder 230V 13kW