Grizzly G0678 8x30: Repair, Scraping and Alignment

[mattthemuppet2]

to be honest so far I've been pretty impressed - the nod was out by a touch, so I sorted that out with a piece of 7-up can between the knuckle and the base, which put it within 0.01mm over the width of the table. All the sliding surfaces are in good condition, no gouges or ugly machining marks, just the usual Chinese way cutter marks on the flats. Backlash is minimal and there's little (0.01mm or so) movement in any of the axes between locked and unlocked. The gibs are different on mine though - they're adjustable from the ends, not the sides, if that makes any difference. I guess it's just the luck of the draw.

 

[AndySomogyi]

Someone just shoot me in the freaking head

Got the knee nice and flat against the saddle and square in the y direction against the column, and I assumed the ground flat on the top of the knee was a reference.

The freaking knee is tilted against the column in the X direction BY FREAKING 15 THOUSANDS OVER 8 INCHES !!!!!

My choices are

(1) pull the knee off somehow and scrape the knee dovetail

(2) hack 15 thousands off the right knee to saddle way

(3) simplest is make the saddle not parallel and hack 0.015 off the right saddle way to compensate for the misaligned knee.

Damn these CRAP machines!!!!

 

[Larry$]

to be honest so far I've been pretty impressed - the nod was out by a touch, so I sorted that out with a piece of 7-up can between the knuckle and the base, which put it within 0.01mm over the width of the table. All the sliding surfaces are in good condition, no gouges or ugly machining marks, just the usual Chinese way cutter marks on the flats. Backlash is minimal and there's little (0.01mm or so) movement in any of the axes between locked and unlocked. The gibs are different on mine though - they're adjustable from the ends, not the sides, if that makes any difference. I guess it's just the luck of the draw.

The gibs that adjust from the ends are tapered and I think can be a better solution. Assuming well done.

 

[AndySomogyi]

The gibs that adjust from the ends are tapered and I think can be a better solution. Assuming well done.

Not sure I follow you. The knee is currently cocked at an angle about the y axis relative to the column. On the knee to column dovetails, the right side is fixed and left side had a tapered gib that provides a tension, but it’s the fixed dovetail on the right that mostly sets the angle.

 

[mattthemuppet2]

I don't think that he's talking about your alignment issue, more that tapered gibs can be better than straight gibs.

For your knee, from what little I know/ have read about scraping in knee mills I thought that the column dovetail had to be scraped in first, then the knee to column dovetail, then the knee to saddle dovetail (square to column in both horizontal and vertical planes). Otherwise there's the risk of chasing your tail. That's all just book and forum learning though, you'd be well off to seek some advice from the pros.

 

[AndySomogyi]

I don't think that he's talking about your alignment issue, more that tapered gibs can be better than straight gibs.

For your knee, from what little I know/ have read about scraping in knee mills I thought that the column dovetail had to be scraped in first, then the knee to column dovetail, then the knee to saddle dovetail (square to column in both horizontal and vertical planes). Otherwise there's the risk of chasing your tail. That's all just book and forum learning though, you'd be well off to seek some advice from the pros.

I really want to do as little as possible to this mill, all I care is that I can make a square part.

My original plan was to just pull the saddle off and clean up the ways, put it back together. I had no idea I’d find such massive alignment issues.

So what I’m going to do now is pull the knee off and get that scraped square with itself. I just ordered one of these frame squares off eBay, and use that to scrape the knee in.

I’ve got the saddle pretty close to being parallel with itself.

But I’m totally going to leave the column dovetails alone, they look decent and I’m not going to bother with it.


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[mattthemuppet2]

that's a lot of work for sure!

 

[AndySomogyi]

Knee’s out, its a lot lighter than I thought it would be, it’s only about 75 lbs, I could have lifted it out by hand easy. But I did make a little plate to hold it and lifted it with engine hoist.

Well, apart from the gib being stuck.

The lead screw to bearing fit wasn’t exactly a slip fit, so had to hold the knee and back the screw downward by hand to pull it from the bearing.

After you pull the knee up most of the way, you can pull the gib out and tilt the knee forward and it clears the head just fine.

 

[AndySomogyi]

Not a good sign then the factory bondos over screws. Not cool Grizzly, not cool.

 

[AndySomogyi]

Here’s what I mean about the knee dovetails.