How to cut hole for fitting in stainless

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Hey everyone, I got some great help here previously when I was trying to find the best ways to drill holes into stainless kegs to weld 1/2 couplings into them.  I used a step drill bit and then made a mandrel to pull through and got a really nice fit after.  Now I am having a new issue I need to solve.  I want to weld in 2" and 4" ferrule like the one shown here.  .  The one is going to be 2" with a 0.65" thick wall. The other will be the same, but 4" with a 0.65" wall thickness.  I just wanted to get some ideas on what might work best.  At this time, I am leaning towards making a template for my plasma cutter and cutting the hole slightly smaller than the ferrule, then using sanding drums or something similar to slowly enlarge the hole until I can get a nice tight fit.
Reply:pull through punches work nice (ie greenlee). grinder with 3 inch cutting wheel,  works too.'14 HTP invertig 221Thermal Arc 201ts'15 HTP 2400'13 Hypertherm Powermax 30Esab 875Esab 251Clark Metal Servicespecializing in stainless steel exhaust systems
Reply:The punches work slick. Since you have a plasma, depending on head size, a short stub of 2 1/2'' or 3'' schedule 40 pipe might work as a template for the 2''. Set on location and walk torch around the inside. 5'' pipe could work for the 4''. What about welding it on and then cut out the inside , done that before. That will also help with distortion too .Thickness is  .65 or .065 ? I think the thinner or that is one heck of a keg.
Reply:Would a punch make it through 16 gauge stainless though?   Punch would be ideal for the smaller fitting if it would.  For the 4" I think I'm stuck going with the plasma.  If the too of the keg is smooth I would definitely weld first and cut after.   Sometimes there are ribs that will get in the way, but I'm thinking plasma before or after is the way to go on those.Last edited by Bassplar; 11-06-2014 at 08:57 AM.Reason: spelling
Reply:If you are wanting to cut into a keg, I have used a holesaw before.  Go slow and use lots of oil.
Reply:yup, holesaw and slow- real slow and carbide burr
Reply:I have a few lennox hole saws.  Any brands or types best for this?  I have a drill press I can fit the keg in too and control the speed and pressure easily.
Reply:I've used carbide tipped hole saws with no issuesAWS 17.1, D1.1 and ASME IX (GTAW)Miller Syncrowave 350LX, Maxstar 150sth, Maxstar 200DX and  Millermatic 252 w/ Spoolmatic 30aMiller buzz box with Lincolin TombstoneThermal Dynamics Cutmaster 38
Reply:I just did this on .130 304L Stainless. Used a 2 inch hole saw, and kept spraying PAM cooking spray on it. Also use PAM on my mig gun and PAM on Drilling. I love PAM
Reply:If using a hole saw, you need to ensure your bit/blade is a bi metal bit.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:FWIW,~John
Reply:ever heard of blair hole cutters before?  http://www.blairequipment.com/holcut...olcutters.htmlmake regular bi-metal saws look like toys
Reply:I use bi-metal lennox saws all the time!color in the shavings mean your going to fast. I set my cordless in 1st gear, and drill holes up to 3" in diameter in sch 40 stainless pipe of all kinds of sizes regularily. slow rpm, and sit on the drill!I really like this stuff too, for cutting ss metal by holsaw or drillhttps://www.fastenal.com/web/products/details/0316633bosses stuff:trailblazer 325maxstar 200my stuff:sa 200fronius transpocket 180100 amp Lincoln w/f97 f350 DITKevin
Reply:Once you start cutting keep the pressure on.If you let up and let the bit/cutter rub instead of cutting, the stainless will work harden in a flash.