Close tolerance holes??

[REVCAM_Bob]

I have to make close tolerance holes i.e. +/- 0.0002 on diameter.

I could bore the holes, but it is kind of a production application with
many holes and various sizes, I don't want to have to "Tweak" in every hole..
the holes are 1.5" diameter to about 3.5" diameter, otherwise I would just ream them. Does anyone have any ideas for a tool that large that would
be like a reamer? Or where to buy large special size reamers?

[Geof]

Have you considered ball sizing?

http://www.precisionballs.com/ReportOnBallSizing.htm

[REVCAM_Bob]

Thanks

[HuFlungDung]

Buy yourself a boring head and bar for every hole. Shars Tool Co has a small selection of boring heads for cheap. Now, these are not "tenth's set quality", so you will have to tweak and fiddle to get them cutting to size. But, it beats resetting one boring head over and over again. I am assuming that your spindle taper is in excellent condition and capable of accurate repeat positioning of the toolholder.

[dertsap]

Originally Posted by HuFlungDung Buy yourself a boring head and bar for every hole. Shars Tool Co has a small selection of boring heads for cheap. Now, these are not "tenth's set quality", so you will have to tweak and fiddle to get them cutting to size. But, it beats resetting one boring head over and over again. I am assuming that your spindle taper is in excellent condition and capable of accurate repeat positioning of the toolholder.

i agree , boring heads would be best on such a tight tolerance ,
what is the hole depth? your going to need something quite rigid to avoid any taper , carb, bars would be best
like Hu said your going to need a good clean spindle to achieve any repeatability or you'll need to tweak every hole

in order to avoid picking up chips or any dirt ,i'd suggest hand bombing the boring heads in and out of the machine after the hole is done
ive seen far too many times guys getting confident with the boring and they end up oversizing the dia because the tool didn t seat properly