Subtleties of climb milling

[projectnut]

I don't have a PM mill, but looking at pictures of the 833TV it appears the backlash is adjusted the same way as my Bridgeport. Here's a link to the Bridgeport manual. Pages 5-5 through 5-10 show the procedure used for adjusting the gibs and table screws. Bridgeports come from the factory with .003 - .005 backlash on both axis.

.https://www.hardinge.com/wp-content/uploads/KneeMill-Parts-Older.pdf

 

[Optic Eyes]

When rebuilding a Bridgeport I always suggested ball screw retrofit, buying ball screw stock and and machining it, and adding a standard ball but, never ONCE did they spend the extra money, imagine climb feeding by hand, no table locks on a bit, and letting go of the hand crank but nothing bad happens, that's a ball screw

 

[benmychree]

When rebuilding a Bridgeport I always suggested ball screw retrofit, buying ball screw stock and and machining it, and adding a standard ball but, never ONCE did they spend the extra money, imagine climb feeding by hand, no table locks on a bit, and letting go of the hand crank but nothing bad happens, that's a ball screw

Or, don't climb mill ---

 

[projectnut]

When rebuilding a Bridgeport I always suggested ball screw retrofit, buying ball screw stock and and machining it, and adding a standard ball but, never ONCE did they spend the extra money, imagine climb feeding by hand, no table locks on a bit, and letting go of the hand crank but nothing bad happens, that's a ball screw

Keep in mind almost all Bridgeport series 1 machines didn't come from the factory with power feeds for the X or Y axis. Ball screws work fine for servo or stepper powered drives because the eliminate reverse table movement when climb milling. However when the table is moved manually it requires the brake to be partially engaged (unless you have a ball screw with a built in anti backlash mechanism) to eliminate reverse movement (chatter) caused by the cutter against the work piece.

Ball screws are not normally recommended on manual machines for this very reason. If the brake isn't slightly applied there's a good chance for chatter and poor surface finish. If it is applied it induces wear more quickly. Over the years we had several Tree and Bridgeport mills rebuilt by the respective factories. In every case they recommended ball screws only on CNC machines, or those converted to servo or stepper drive tables.

 

[Downunder Bob]

When I was an apprentice back in the early 60's I was taught that these machines were not designed or intended for climb milling. It was drummed into me that both horizontal and vertical spindle machines should only be used in conventional mode at all times except for very light finishing cuts.

Over the years I have seen a number of machines damaged even wrecked by climb milling.

As a result I cringe every time I see climb milling being used or advocated.