back counterbore

[Tmoose]

we may have to back counterbore a dozen or so holes.
Presently they are 2.000 diameter, but will probably have to go to 3.3 or so inch, and get a 5.6 inch spot face to boot. The spotface will be mainly to provide flat surface by removing a flange radius that starts about the 4 inch diameter point. At first the spotfacer will hit a small sliver of a section at the cutter OD. After feeding about 0.15 inch it will clean up 100%.

The holes will be enlarged in a big machining center with a horizontal spindle.

The back counterbores on the Internet are kind of complicated, and probably pricey too.

Any suggestions how to handle this?

I'm thinking of poking an arbor thru the hole, offset a little, then mounting a 6 inch slitting saw on the arbor.

 

[BillPSU]

A flipout back counterbore or a arbor mounted counterbore tool which is manually loaded at each hole. The flip out tools are relatively expensive and the arbor need manual intervention. How many parts will determine which is best to use. For many parts the flip out. For a few parts the arbor mounted. I have given two links but I have never used either product. Your size is very large and may be difficult to get a standard tool.

http://www.lomas.co.uk/spotface.html

http://www.steinertechnologies.com/

 

[ornerynorsk]

If you only have a dozen of these to do, and on a horizontal no less, just fabricate a toolhead with a fixed toolbit to go on a through arbor. You need considerable rigidity in your setup. I've had to do several of these when repairing large woodworking machine castings. Good luck!