fishmouth cut for large pipe

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Here is a tool I made years ago for coping large pipe with bimetal holesaws. I have done up to 3 1/2" sch 40 easily with it.  It is a modificaction of the holesaw tools already on the market, but I take out the guide bit and make a shaft to keep the bit from chattering.  Also you don't have to cut the whole pipe, usually I just cut about 1/2" off so the entire process takes about 60 seconds. The pic shown is a deeper than normal cut for 2" pipe to fit on 2 1/2". Attached Images
Reply:I made another one that cuts at an angle instead, same principal usine a 1/2" rod to steady the hole saw.
Reply:You can use the same jig to cut a through hole (takes a little longer) for passing one pipe through another.  This is 2 1/2" sch 40 with a 2 1/2" hole for passing 2" sch 40 through. I use it for commercial swing set brackets. Attached Images
Reply:I like that.  Nice and simple.  The pin act as a stop, so you precisely how much is taken off each time. Cool.  Have you done one for angles notches? Thanks for sharing.Last edited by tapwelder; 02-13-2013 at 12:22 AM.
Reply:I started using the pin for a stop, but then found I could do just as well with a spacer, cuting only about 1/2" into a 2" pipe. That results in a small moon shaped piece cut on both sides and a longer horizontal piece.  It takes much less time and still makes a good looking weld.  I have made an angle jig using the same idea, but don't use it as much.  The main advantage of this design is I can cut any size pipe.  The commercial "joint Jigger" type of tool is limited to 2" OD. I'll try to find a picture of both.
Reply:Same idea for coping 2" x1/4" aluminum square Attached Images
Reply:Damb Bart,You're a feakin genious!!I tried "fishmouthing" some tubing last night on the drillpress and couldn't figure out a solid mount, so gave up and grabbed the plasma.I need to start reading more of your posts Lincoln SA 200Esab Caddy 160Thermal Arc 201TSMiller Dialarc HFI don't like making plans for the day because then the word "premeditated" gets thrown around the courtroom....
Reply:I;ve cut 3" pipe this way.  Again I don't tave a full cut, just a 1/2" or so moon off each side.  It goes pretty quickly.  You can do a full cut, but I haven't found it to be needed.
Reply:Originally Posted by blackbartI;ve cut 3" pipe this way.  Again I don't tave a full cut, just a 1/2" or so moon off each side.  It goes pretty quickly.  You can do a full cut, but I haven't found it to be needed.
Reply:Once you have the angle jig centered on the drill press table with either the 1/2" rod or a drill bit, tighten it down on the table.  Mine has bolts that got through the X slots,  After that, put what ever bit in you want.  As far as getting several in a row centered on the same axis,I draw a line down the pipe by laying angle on top of it.
Reply:Here's an "ad hoc" notcher I made some frames for chain link fence with.  Used on 1-5/16" galvanized fence tubing, which is a lot like EMT.Bottom plate was a 6x6x1/4, the two sides were 1/4x1-1/2" strap, the top was 5/16x2-1/2, four big tacks hold it together.Line up the bit with the hole, clamp it down.  Bring the tubing up to the side of the pilot bit, clamp the sides.  Drill and repeat.  Attached Images
Reply:Thats a good design too, anything to keep the hole saw stable.  I do find I can get by with cutting out less, leaving more of a horizontal section and making the process faster. On tubing that size I would probably cut 1/2" or so.  Cutting too much also feathers the sides so the weldable area is much thinner.  I like it, if you did a lot of a specific angle you could weld the guide at that angle.
Reply:Also, deeper Bimetal holesaws are available (McMaster Carr is one supplier) for doing angel cuts with FabnFuns design.
Reply:Originally Posted by blackbart ... I do find I can get by with cutting out less, leaving more of a horizontal section and making the process faster. On tubing that size I would probably cut 1/2" or so.  Cutting too much also feathers the sides so the weldable area is much thinner.  I like it, if you did a lot of a specific angle you could weld the guide at that angle.