Plowboy:

Funny how farmers in close vacinity of one another seem to have simular practices.  I see you are in KS, and I am in the panhandle of TX.

I understand your reply, and I appreciate it.  I may weld some tubes on the back side of my c.c. chisels.  My c.c. chisels are made by Nichols.  If you are thinking about getting a set (or another set) to rig up some NH₃ tubes, these Nichols would make a fine choice.  I have run mine over hundreds of acres, and they show very little wear!  I can not believe how hardy these chisels are.  It would require a fair amount of time & labor to fab. the NH₃ tubes, so one would want to start with a quality chisel.

Below is a picture of my chromium carbide chisels.  I got this pic. from Nichols' site.  I do not [currently] have the sweep(s).  Again, it is notched so you can mount the sweep & chisel at the same time...do two things at once..(if I had the NH₃ tubes welded on, I would be doing three things at once!)

So, you think that things centered at, or about 18" will suffice?  I have chisels for every shank (OEM is set up on 12" centers, as you well know), but I do not have enough outlets on my NH₃ manifold to go with 12" (or even 18") centers.  I could easily put a "Y" or "T" in each line, and effectively double my outlets.  If starting with a "blank sheet of paper", what distance would you use for center-to-center?  A lot of NH₃ 'rigs' use 2 feet as the center-to-center distance...so you sure might be barking up the right tree at 18 inches..

One more thing: as far as mounting the tube, did you burn the tube directly to the chisel, or use something like a half chain link (at top & bottom) to hold the tube on?

Thanks