PSG612 Z Accuracy Improvement

[timbee]

I don't post to forums very often, tho I do read here all the time. There is loads of good info on the Tormach forums here at cnczone and I thank you all for that. So it's time I repaid with a contribution. Excuse me if this has already been done by anyone.

I bought the PSG612, because I wanted to do precision grinding. The Z-axis downfeed is so mushy. I can move it down .0005, give it a tap on top of the column with my hand, and it goes down another .002 - .003 . Not good ! I checked backlash and the few other adjustments that are possible on this machine. Nothing changed.

Started to wonder if maybe the counter weight was making the Z column 'float' in the space of backlash. I moved Z all the way to the bottom of its travel and re-installed the bolts the lock the counter weight in the shipping position. Wow, what a difference. I can still make it move down about .0005 with a hand tap on top of the column, but I think that's acceptable. Moving Z up without the counter weight isn't that difficult.

I'm making a set of parallels, After checking them with a Starrett .0005 Last Word, I can't detect any measurable variance in height after making this one little mod.

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[79rallysport]

Started to wonder if maybe the counter weight was making the Z column 'float' in the space of backlash.

So your hunch was correct? Did you essentially disable the counter-weight? I don't have a grinder so I'm not familiar how it works, but I am considering getting one so I want learn as much as I can about maximizing its performance.

[timbee]

Yes, the counter weight is intended to make it easier to raise the z column. I disconnected the counter weight, it made all the difference in the accuracy of the machine.