Boring Advice Sought

[jorogi]

Tools at hand,
Gorton knee mill,
News rotary table,
Narex boring head,
Accurite DRO,
new end mill.
All of it is in good shape.

Job,
Block of 1 1/2" steel needs a clearance through hole, with a counter bore on either side for bearings to press in and run concentric with each other.

Granted the weak link is me but the question is how would you do it. Bore the counter bores with the Narex, or cut them on the rotary table, and why ?

 

[Tom Kitta]

If you have a lathe - use that.

If you do not have a lathe use a milling machine with a boring head.

Drill hole to close to required dimensions.

Bore the hole out very slowly if you do not have reamers.

You need some kind of boring bar that your boring head takes.

You don't need to cut to dimension on both sides - you can just bore to size in one go and then keep bearings apart with a pipe. If that is not possible you will need to make sure you place your work exactly in the same spot - this may be tricky depending on how concentric you want things to be.

If bearings move with a lot of force or crunchy you made the hole too small. Lathe comes handy with emery cloth here.

 

[PeterT]

Based on what you've described, a lathe setup is probably more efficient as long as you can hold it & register the part reliably. Boring heads are good at what they do, but it takes a lot of cycle time to increment, bore, repeat.

Left, you can do 4 features in one setup: face + clearance hole + bearing OD & c/bore depth (orange = 4J chuck jaws for ex)

Right, flip the part & essentially repeat. You can maybe even utilize your prior bearing dial settings if bar remained in position. The trick is registering the 2nd bearing hole to the first concentric & parallel. Ideally you want to reach in there with DTI to set concentricity. If that's not practical, think about what is is most accurate. The clearance hole is probably less reliable if you just hogged it, but if you skim bored that too in step-1 it would be better. Maybe a dummy shaft temporarily landed in the bearing to indicate off? Also consider backstopping the part on the rear face which is machined face vs just counting on the jaws. Good luck!