Lathe groove bar killing grooves

cnczack · Sep 14, 2020

We have a 1" sandvick groover using a vrg125 insert to groove a .125" deep groove. Every machine the bar has been set up on has killed the groove by .03" on the 3rd attempt the operator adjusted his offset -.03" before running and on the rough out hit the tolerance. It seems to me that the boring bar geometry is wrong after having 3 separate machines and operators setting up for this job. Especially since there are 2 milled flats on the bar only leaving 2 ways to set the bar up. As far as the program goes its exactly as it should be as far as size on the rough out and finish.

What could be the reason for having this issue? Any suggestions would be appreciated!

SMT · Sep 14, 2020

What is off .03? The groove width, the location? Is it an od or id groove? Is the diameter off .03?

Fancuku · Sep 14, 2020

SMT said:
What is off .03? The groove width, the location? Is it an od or id groove? Is the diameter off .03?

He/she said groove bar so I assume it's an ID groove.
I highly doubt that the geometry of the groove bar is that far off to cut .03" deeper (I am assuming it's the depth that is the problem). Most likely the bar is not being seated in the correct orientation inside the tool holder.

doug925 · Sep 14, 2020

Fancuku said:
He/she said groove bar so I assume it's an ID groove.
I highly doubt that the geometry of the groove bar is that far off to cut .03" deeper (I am assuming it's the depth that is the problem). Most likely the bar is not being seated in the correct orientation inside the tool holder.

Unless it was a Valenite brand. I have purchased (within 2-3 years) two different boring bars, and one turning tool from them.
All were junk! The flats were not clocked correctly, and the insert seat on the turning tool was rough, and not flat. :confused:

***ETA
Maybe since Walter purchased them (no idea when) their quality has improved.... :blahblah:

doug925 · Sep 14, 2020

OP,

How is the grooving bar offset, being calculated?

Touch off tooling arm?
Cut/measure/ adjust?
Tool setup back in the crib?
Going off MFGR's specs?

I can see some tweaking in after tagging your bar (or however you handle tool setup) but 0.03" ?? :eek:

Going out on a limb, do you work for a very large shop? Do the operators handle setup, or is that specific to a S/U guy?

Doug.

cnczack · Sep 14, 2020

The diameter was off by .03" too big. I went and grabbed a trusty Mueller gauge to measure it myself and turns out our mic that we were using to check the wall thickness (inspections micrometer) had been damaged and no one had known. I appreciate everyone's response!

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