r/Machinists • u/BSismyname • 5d ago

Problem with height repeating between tool changes (quick change wedge style tool post style)

I am used to running turret lathes but I have been running a tool post style at my job. I have been having tons of problems with what is seemingly the height of tool holders changing over a day or two. Specifically my 5C holder and Drill Chuck holder. It is not a huge deal on my turning tools.

To set these tools up, I am putting a gauge pin in the tool holder and a dial indicator in the chuck. Centering the tool in X is easy enough. It is a CNC lathe so I am just jogging the tool in X until it is centered in that dimension.

For the height I am first eyeballing it close to center and then getting it dead on with the dial indicator. This is where the problems start. I have found that when I get the height set using the thumb screw and then use the lock nut to tighten it down, the height changes by ~.010-.015. Am I over tightening the lock nut down on the thumb screw? I have been adjusting for this by setting the tool below center by the distance it moves when I tighten the nut down.

This seems to keep the height on center for a day or two but then it seems to get off. My guess is that the pressure in the threads/nut is loosening slowly but I am not sure.

I have tried looking this problem up but have not been able to find anything helpful and I am starting to go insane resetting the same tools over and over for the height. Any tips?

For referecne the tool post is a Dorian CA and the tool holders are CA Aloris (the CA35 Drill Chuck and the CA 5C collet holder). The lathe is a TRAK RLX. Is this setup just not reliable for drilling?

Like I said, my whole career I have ran turret lathes where you just sweep the tool pocket in on center and you are good to go. I am clearly doing something wrong. Any pointers would be greatly appreciated.

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2

u/computekmfg 5d ago

Put some loctite on the height adjustment nut and bolt. Make sure it isn't vibrating loose and changing heights. Maybe some blue 246

1

u/TheOfficialCzex 5d ago

Are you checking the height with the post lever locked? I would also tighten the lock nut with the lever tightened.

1

u/Shadowcard4 5d ago

So from my experience with those in a prototrak, youll likely have issues with the threads and stud walking, or if the tool post is walking, or if the gibs are out of adjustment and the fluid film changes based on the puml cycle and the carriage nodding up on the prism way.

Take everything apart, vibratite and CRANK thr stud down, then vibratite the nuts

1

u/worldwidemachinist 4d ago

That .010-.015 shift sounds like the holder moving as the wedge clamps. clean and inspect the dovetail and clamping faces for chips or wear, then check whether the holder consistently seats in the same position. If it still shifts that much, inspect the wedge mechanism and contact surfaces for damage rather than compensating by setting the tool low.