Mill table w/in .003 overall...can I improve that at home?

[Bolster]

I purchased an X3 mill from Grizzly, and the table is within .003 end-to-end (actually .0027, best as I can tell). Spec from Griz is .002, so they are saying "send it back." What a huge hassle, and loss of cleanup time that would be.

Unfortunately there is a diagonal .001 dip or arc across the table, about 1" wide, as if it's where a polishing machine spun down or something. (If it weren't for that, I'd be at under .002 all the way across.)

Is there any way I can improve flatness of the table, without the heroics of packing up the machine? Here are some options I'm considering:

I have a 9 x 12 grade B stone, flat at .0001 across the surface, can I mount sand paper to it and move it across the table, spending more time on the high areas, and stopping to measure progress every once in awhile?

I have heard of lapping on float glass. I have aluminum oxide powder of various grits from another project. Is that a possiblity?

What does one do in this situation?

[Bruce Griffing]

Why not just return the table? Easier to pack and ship, etc.

[doctor demo]

Bolster, don't take this the wrong way but.....
Why bother, it would seem that it would be rarely that anything You are working is going to fall into that ""polishing mark'' and cause trouble. Especialy if You have a vise on the table like I do 99.9% of the time.

Steve

[Bolster]

Why not just return the table? Easier to pack and ship, etc.

That was my idea, too. They said "No. The table is matched to the machine." (Mumbling 'bll-crp' under my breath.) Doctor Demo, you may be right. It'll be interesting to see what the consensus is.

All the same, the question still stands:

"Can you improve the flatness of a mill table without sending it out for surface grinding?"

[doctor demo]

"Can you improve the flatness of a mill table without sending it out for surface grinding?"

You could scrape it flat, but I wouldn't want to except for the learning experiance and then maybe not.

Steve

PS. See if Griz will make it right with some other comp.

[oldtiffie]

Bolster, don't take this the wrong way but.....
Why bother, it would seem that it would be rarely that anything You are working is going to fall into that ""polishing mark'' and cause trouble. Especialy if You have a vise on the table like I do 99.9% of the time.

Steve

I'd agree with that Steve.

Most mills only use the middle third most of the time.

Most jobs will span that "polished defect".

Many vises may be "out" that far as well - even without "moving-jaw ""lift"".

Most work has a realistic tolerance of more than a couple of thou anyway.

If I was setting up for the inferred level of accuracy, I'd be checking, packing and shimming as required.

That "error" could be due in part at least to insufficiently adjusted "X" gib clearances as the table will tend to "drop" at the end that is standing out furthest from the saddle. There are other potential causes.

I am quite appreciative of the disappointment of having that error on a new machine, but sometimes I at least have to "wear and eat" and where necessary make allowances and find and use "work-arounds".

[RB211]

So the table from end to end is off by less than the width of a human hair?
Tell me what your going to machine where that matters? I have this same mill, and I can tell you that the table should be the last thing on your mind. Why don't you measure how much deflection you get on the head while side milling some steel with a 1/2" 4 flute endmill with a depth of cut greater than .010?
I have a DRO on mine, and I can easily make parts to .001 no problem. 99% of the time I don't need to...
Lets say my table is off by .004 from end to end? Oh damn... I better put all my projects on hold, nothing will ever come out right...

[darryl]

Hmm. That's not much of an error, but why shouldn't you make an attempt to flatten it a bit more- you're willing to give it a go anyway-

What would I do in that situation? I'd be leery of sending it back for either correction or replacement. It might not get any better- it might even get worse, who knows. I'd pull the table off and sand it just like you were thinking of doing. A few careful passes across the sandpaper taped to the surface plate, and you'll see the picture easily. I would NOT leave the table on and muscle the surface plate over it, if that's what you were thinking of. You'll round it over for sure.

Maybe it would be overkill to do all this- I dunno. I think a .003 thou deviation is quite a bit- if you're trying to square something up, make the sides parallel, etc, 3 thou can mess you up. Why bother with precision ground 1-2-3 blocks, or precision ground parallels, or toolmakers vise, when your reference surface is not flat.

[gwilson]

I sent a Valumaster mill back to MSC. The table angled out of the horizontal by something like 2 3/4 thousanths from the front to back of the table. It could have been more,I can't recall now. It was at work,but I had fork lifts,and large rolls of packing plastic wrap to re-coccone it. Still a PITA.

I won't be buying another of those!! the table is supposed to be a little higher in the front to allow for cutting pressure,but this one was too far out to suit me.

[Bolster]

So the table from end to end is off by less than the width of a human hair?

You must have fat hair...mine's thinner than that.

It's the 1" wide dip that gets me most...it's sharply defined, and often where I want to set a square to measure tram. And it also messes with my tram readings when I'm swinging an indicator in a circle, and hit that point; finding a .001 deviation in the table when the diameter of swing on the indicator is 5" makes you think you're out of tram. I find myself cranking the table around to the flatter spots to get better readings. So naturally, I wondered if I could flatten it myself. As you can tell by my original post, I don't think it's a big enough deal to return. OTOH, it is out of spec, according to Grizzly.

Gwilson, are you saying the tables are purposely not flat, in some cases? My table gradually slopes up on either end. You think that's on purpose?