Making Cope Joints in Steel

This would a flat flanger on  the bottom are commonly used for  mounting machines and carts the Koch  joint lets you make a frame like this  without special tools as with any frame you want to make sure we mark the pieces  out accurately so we can get all the  pieces the right size and then we can  cut the pieces to the right length and with my square ends even with the pieces cut to the right dimensions we can't get  a flat bottom to this frame you get.

 a strong flat bottom to this frame we need  to remove the material that's under the  top piece here the custom remove that  material is what we call a kolbe to make  a truly square frame we double the  thickness of the material here in this  case a quarter of an inch and then cut  opposing side pieces a quarter of an  inch shorter than the rest using the piece that we want to fit into the COPE  as a guide you scribe off a cut line.

We have to remember that this cut line is  outside of the piece that we want to put  in there so we make the cut it has to  stay to the inside of that line you can  make these cuts any way you like I like  using the jigsaw because it lets me be  very precise you can see that I kept the  cut to the inside of the layout line if  I need to I can always sweet miss up  later what a file or grinder now one  more cut flush with the other side of  the angle and a cope is done.

Now we can  test fit two pieces and see if we need  to do any filing or grinding is  sweetened and join up this one looks  fine when the cope is cut right even the  south side edge comes out flush I like  to use my best angle clamps whenever I  can for this kind of work and so lets me  tack the pieces up and keep them very  square my busy welding maintenance also  do a good job of holding the pieces in  the right orientation for tacking and  welding once all the pieces are tacked  together and I'm happy with the way the  frame is and I can go ahead and do to finish welding.

I usually do all the  welding on the outside of frames like  this so we can keep that in sight flange  nice and flat it gives us a smooth solid  surface for whatever we want to put in  there then if the project needs it we  can grind all the welds flat and the  framing is done and that's all there is  to making cold joints this is very easy  and once you do it a couple of times it  goes real quick....