How to?

[Aukai]

I have 2 parallel 1" aluminum pipes that are staggered vertically, offset over each other. I think the offset was 3/4", I have bar stock that will make a flat mounting surface between them the OD is 1.312-1.315. I'm thinking a convex cutter on opposite sides to center the bar for welding. What radius cutter do I need, or is there an easier, different way to do it, maybe just mill the offsets of the bar stock square?

 

[Chewy]

If I read you right, you want to put in a 1-5/16 diameter (.656 Radius) concave into the ends of the bars and have a nice tight fit for welding. That is a real odd ball size, so I would use a fly cutter. You could layout the arc and then hand mill up to the lines or make/use a small flycutter or boring bar set to correct size to do the arc. You start at the edge and feed in until you get to the right depth. A 16mm endmill is a shade to small and 17mm endmill is a tad too big to just plunge cut. You could also layout the arc and use a small grinder up to the lines. You don't have to be perfect because the weld will fill in the gaps.

 

[aliva]

If you have a mill and a boring head. Clamp the steel bar in the vise with an 1- 2 inch stick out. Move the table till the end of the steel bar is on the spindle center line. Move the table the radius of the pipe your using .656 from the bar end. Install the boring head and boring bar, adjust the boring head till the boring bar just touches the end of the bar in the vise. The boring head now has a radius of your pipe.( .656) Don't adjust the boring bar anymore. Now start cutting with the boring bar by advancing the table into the the work Stop when you've reached .656 travel. A perfect .656 radius. If you still unsure check Oxtools video scroll to 30.49

 

[Chewy]

On a small arc, I would do (and have done) just as Aliva said. You can only advance .010-15 at a time. If you were to try this on say a 3" arc, it would take forever. You layout the arc and scribe it. Then you set up as Aliva said. You then set 0-0 on DRO. Raise the spindle and remove the boring bar. Put in an end mill and hog out material just shy of the scribe line. Then go back to 0-0 and put back in the boring bar and proceed in. Even on a very small mill you can do arcs 4-5" diameter and even cut on angled material to make a dish.

Almost everybody has a video out on doing this, In addition to Oxtool, Jo Pi & Mr Pete have videos for this and I am sure other people can add more. Post a picture of your results. Good luck!

 

[Aukai]

Thank you both, waiting for material to show up from America.....