Grizzly Mill problem

[Kim]

Don, this makes me unduly happy.    Happier than I have any right to be since you still have a lot of work ahead of you to take off the head, crate it up and ship it back to them.  But at least Grizzly is responding to you and to their customer base.  I sincerely hope they make you happy!
Kim

[steamer]

Good to hear Don!

Dave

[sshire]

That is excellent! They certainly did a 180 after the "out of warranty" BS.

[b.lindsey]

Not the ideal solution, but certainly better than their first response. Overall that' s good news Don!!

Bill

[Dave Otto]

That's good news Don, hopefully they can get it fixed for you.

I was thinking to myself that the problem would be more likely with the bore than the OD of the quill. If this is the case it seems that for them, the best avenue would be to just give you a new head casting. It will be interesting to see what they find wrong and what they do to remedy it.

Oh; and you have my sympathies on having to be with out your machine, that is really going to suck. 

Dave

[PStechPaul]

I have never checked runout on my Harbor Freight 42976 Mill/Drill machine, so I did so this evening. I put the magnetic base and dial indicator on the table and adjusted the indicator on the lower right side of an end mill holder in the spindle:
 

 
With the spindle locked it the retracted position, I could barely get 0.0005" deflection with modest pressure on it. And it seemed to be just "spring" from the post and the head, and it moved back into position when released. With it unlocked, I could get about +/- 0.002" deflection. With the spindle/quill fully extended (about 3.38"), and unlocked, I got about +/- 0.004" to 0.007", but with it locked I got about 0.002" as shown below (and it also sprung back when released):
 

 

 
Yeah, I have a lot of clean-up to do.    But I just wanted to see how my cheap machine (about $600 in 2004) compared to yours, or others. I have not even taken very good care of it. So I can see where you really do have an unacceptably sloppy machine and you should be able to get it corrected by Grizzly. I have heard that Chinese machine tool quality is very much "hit or miss", and I think it "misses" more often than not lately. At the time I bought my mill and lathe, many such tools were "made in Taiwan". Good luck with your repairs. 
 

[old-and-broken]

I've been following this topic with great interest and would suggest a possible source of confusion and error that is possibly being overlooked by some.

With the quill and spindle fully extended leverage multiplication is what I suspect you are reading with the increased spindle movement.  My suggestion would be to place a brace, perhaps a small screw jack, between the quill body and the vertical post on which the head is mounted.  This would remove any movement caused by flex between the head unit and the upright upon which it moves, leaving only the movement of the quill and spindle.  pressure would be applied toward the brace.

AND the dial indicator base/holder should be mounted on the vertical brace, not XY table.  This would remove any flex introduced from motion between the table and the vertical upright when pressure is applied.   That should leave only the slop of the spindle as a reading on the dial indicator.

Mark

[PStechPaul]

I agree that something like you suggest may be the best way to determine the actual loose play of the spindle and/or the quill. And here I am assuming that the spindle is the moving part with the MT2 taper into which the end mill holder inserts, while the quill (which may be termed the "ram" on my mill/drill) is the sleeve which houses the bearings for the spindle, and which slides vertically in the head.
 
I don't know how the quill is locked in the Grizzly milling machine (Don has the G3103), but on mine the head casting has a slit which allows it to be compressed evenly around the quill, or released to allow vertical adjustment. The lever can be adjusted to provide a snug fit at the expense of easy raising and lowering of the cutting tool into the work. For most milling operations I have the quill locked at specific height, but I can adjust it slightly if the grip is not too tight, by tapping on the bars of the handwheel.
 
When actually milling, what really counts is the flexibility of the entire machine, as evidenced by any displacement in the X, Y, or Z axes. The X axis, from left to right, exerts torsional force on the column in the rear, and will cause motion in that direction, but also causes some motion in the Y axis as I have seen dramatically when the column has been loose enough to turn. The Y axis, forward and back, exerts a bending force through the table, calumn, and head, which actually causes motion up and down in the Z-axis. Mostly I have found that the milling machine vibrates as it is cutting, and the frequency of oscillation is affected by the cutting speed and the geometry of the cutting tool. The mill probably has one or more resonant frequencies where the vibration can be accentuated, which may be reduced by changing some of the parameters.
 
[edit] From the manual for the G3103, I still cannot tell exactly how the quill is locked in place. I see the locking block and locking bolt in the parts breakdown, but it looks like it might just be a cam that impinges on one side of the quill. Don's photos don't seem to show this very well, but I don't see any slit in the casting and there is just a small slot where this may be implemented. In his mill (and most serious milling machines) vertical movement is provided by means of adjustment of the knee.

[steamer]

Let's be careful here guys.   If we're going to measure the quill movement, mount the indicator to the quill housing, not the table....you'll end up measuring the column deflection as well as the quill movement.

These little machines aren't K&T production mills, they're made to a price for the home shop market.   Hell my Clausing can't be expected to be as rigid as I would hope....My Van Norman was though.

Dave

[b.lindsey]

Excellent point Dave!

Bill

[Don1966]

Guys I appreciate all of your inputs, but if you look at the first photo I was moving it with my fingers, my thumb is on the housing while pulling. You can actually see it moving when pulling it.

Don

[steamer]

OK Don, couldn't tell.  Thanks.

It's fine to be critical of a short coming.  I'm all for it!....just lets be careful of how we all measure it.    I say this as I want to be fair, and not cause a panic!....In all likelihood, everyone's machines with the exception of a couple are just fine, and fit for purpose.     If they are bad....they're bad and get to the bottom of it.

I once had a discussion with someone about the inherent stiffness...or lack there of , of a lathe, especially a light lathe...."Why can't they build them lighter? , the cutting forces are very low!"........   I told the person that it's stiffness, not strength that matters here.   I told them to mount an indicator on the tool post and zero out against the OD of the chuck with the belt loose.    Then.....without touching the indicator....tighten the belt!

They were amazed how much stuff moves....the lathe worked fine for what it was....but they do move around.

Try that trick with any of your lathes, big or small...you will be surprised as well.  Does that mean it makes bad parts?....No...It's just real world physics in action.  Just don't freak out about it...it's making engines just fine

Dave

[Don1966]

Just an update on the mill. Grizzly has sent me an authorization to return my mill head to be either repaired or replaced depending on what they find. I have been issues a return number and the shipper has sent me the paper work to get it back to Grizzly. All I have to do is crate it and have it picked up or bring to shipper. When it is returned I will let you all know. So far things are looking better.

Don

[steamer]

Good to hear my Brother!   Keep us informed!

Dave

[Don1966]

Just to let you know I recieved a email today saying my mill head has been shipped. It doesn't say if it was fixed or replaced. So we will see when it arrived what was done to it. I will keep you posted when it arrives.

Don