Rectangular Parts In A Round Machine Day.

[Wreck™Wreck]

I ran all of the rectangular and square parts that needed lathe work today, 19 parts combined. Multiple parts are made faster in a lathe then a mill with a boring head especially if internal retaining ring grooves and multiple diameters are involved, we also do not have a mill that will interpolate accurately the given +.001 -.000 bearing bore tolerances including Haas and Fadal 3 axis machining centers.

The blanks were milled to size and a hole reamed at the proper location so that I could indicate the parts in the 4 jaw. I milled pockets in soft jaws .100 deep X .100 wide. these parts are thin being 1" or less. Got them close to center using a live center in the tail stock pushed into the hole against the jaw pockets then tightened the jaws lightly and indicated from there. One excellent practice when using a 4 jaw on repetitive parts is to mark 2 of them that you will open when changing parts, the part will remain close to correct position but will still need to be indicated, I use a sharpie marker for this.

The part in the picture (8 total in 304 SS) has a 1.125" +.001 -.000 bore X .750 deep then a .88 bore X .780 deep then a .65 bore through with an internal retaining ring groove .625 out from the .750 bore depth -.005 +.000 and the groove depth has a ± .004 tolerance. The tool in the pic is the internal groove tool.
All in all a PITA

 

[john.oliver35]

Sounds tedious! I'm curious, did you remove the part after each feature to check dimensions, measure them while in the lathe, do the whole thing then check it, or ?????

 

[Wreck™Wreck]

Sounds tedious! I'm curious, did you remove the part after each feature to check dimensions, measure them while in the lathe, do the whole thing then check it, or ?????

It is a lathe, each feature can be measured from the front in place, had to change parts because there were 8 of them, never un-chucked them until they were finished.

With such bore dimensions I do not like changing tools even with a QCTP but is was unavoidable due to time constraints on these parts.

 

[john.oliver35]

Thanks - did you use telescope gauge for the deep features?

 

[Wreck™Wreck]

The deep bores were ± .005 so yes, used a Mitutoyo dial bore gauge set with a micrometer for the close bore, made the retaining ring groove at max Z tolerance and max width with the ring groove diameter slightly smaller so that the ring isn't loose in the groove when installed.