Pm 940v

nighthawkFmobil said:
I guess at this pount this has become somewhat of a journal.

After last nights post and this morning before work i did more test on the column and head. Overall the test were good. Im finding my magnetic indicator holder could be playing a factor. Im also finding my nod to be a heck of a lot less. Makes me winder if the gib wasnt seated properly.

After cleaning everything up and getting it back together its definitely running a lot more smoothly. For right now i have the gibs tight but im not sure its neccessary. Probably going to do ankther 40 test lol then see if i can get the spindle to table within acceptability. Fingers crossed, i could use some hope right about now. Glad i got some.

I think im realizing there's multiple factors with a machine like this when trying to achieve decent repeatability as well as smooth operation(how it feel manually) and function, aside from how nice and tight of a fit the dovetail/gib matches up. B2 you were right about the gib not being a clamping force. I learned much about that. Is it acceptable to put loctite on gibs? Not really confident enough in my adjustment but i could see it being helpful. Maybe a washer could have same effect in my situation
Click to expand...

NEVER LOCTITE!

You will want to adjust it in the future. The proper way to do this is to loosen the screw at the gib small end. Then tighten from the big end until you get it where you want it. Then tigthen the small end back up. The gib is then held in the proper position by the clamping of the screws pinching the ends of the gib towards each other. Hence my need for the washer with the finger sticking into the gib hole. Not pinching toward the ways as is happens when the little end of the gib gets chewed off. The way surface of the gib is scraped (certain amount of roughness) to leave grooves for it to hold oil. This tends to prevent as much wear on the ways. At least that is the theory. I also realize that for flat surfaces only 3 points actually make contact at a time, unless one of the surfaces bends. Think legs on a table. After operation these points tend to wear down and become more flat to give more surface area of contact. If the points are really high then the gib may need to be retigthened a bit.

In my bad gib case, I removed the gib and laid a 0.005" shim along the non-way side to take up the space. This moved the gib ends up where the top screw could be adjusted. I then added the washer with the finger to the bottom screw to hold the gib from moving up and down in the saddle.
The taper on my gib thickness is about 0.0088"/inch. This means that a shim of 0.005 will cause the gib to be about 0.005/0.0088 ~0.57" higher. I measure the taper directly from the bad gib as well as down the gib hole. So for a shim I actually used a piece of Al tape which had adhesive on one side. I put the adhesive against the gib (non-moving way) side. So the Al was then toward the saddle clamps. Not ideal as the clamps would cut right through it to the gib material, but I do not use these screw clamps anyway.

So the gib is working until I made another and the mill works. I have made a lot of thing, but many of them were before I realized I had such a bad gib! My real issue is that the column ways spacing variation.

My z-axis nodding is still about 0.001 to 0.0015. I am sure I could make it smaller by tightening the gib, but then I would be concerned about the gib tightness when the head travels all the way up to the top of the Z-axis. Fortunately, I seldom do that either.

Dave
 
B2 said:
NEVER LOCTITE!

You will want to adjust it in the future. The proper way to do this is to loosen the screw at the gib small end. Then tighten from the big end until you get it where you want it. Then tigthen the small end back up. The gib is then held in the proper position by the clamping of the screws pinching the ends of the gib towards each other. Hence my need for the washer with the finger sticking into the gib hole. Not pinching toward the ways as is happens when the little end of the gib gets chewed off. The way surface of the gib is scraped (certain amount of roughness) to leave grooves for it to hold oil. This tends to prevent as much wear on the ways. At least that is the theory. I also realize that for flat surfaces only 3 points actually make contact at a time, unless one of the surfaces bends. Think legs on a table. After operation these points tend to wear down and become more flat to give more surface area of contact. If the points are really high then the gib may need to be retigthened a bit.

In my bad gib case, I removed the gib and laid a 0.005" shim along the non-way side to take up the space. This moved the gib ends up where the top screw could be adjusted. I then added the washer with the finger to the bottom screw to hold the gib from moving up and down in the saddle.
The taper on my gib thickness is about 0.0088"/inch. This means that a shim of 0.005 will cause the gib to be about 0.005/0.0088 ~0.57" higher. I measure the taper directly from the bad gib as well as down the gib hole. So for a shim I actually used a piece of Al tape which had adhesive on one side. I put the adhesive against the gib (non-moving way) side. So the Al was then toward the saddle clamps. Not ideal as the clamps would cut right through it to the gib material, but I do not use these screw clamps anyway.

So the gib is working until I made another and the mill works. I have made a lot of thing, but many of them were before I realized I had such a bad gib! My real issue is that the column ways spacing variation.

My z-axis nodding is still about 0.001 to 0.0015. I am sure I could make it smaller by tightening the gib, but then I would be concerned about the gib tightness when the head travels all the way up to the top of the Z-axis. Fortunately, I seldom do that either.

Dave
Click to expand...
Im starting to get excited. With your help along with everyone else my 940 is consistently in my spec. Of course ill keep testing but i think ill finally run an endmill tomorrow. Now that ive almost torn her totally down and have methods to move all the parts solo. I really hope this mill works out like my chinese 1228....
 
My column was leaning to the right about .015 in comparison to my table. I shimmed the right side up and i think im finally aligned head to column and column to table.

There's a good amount of paint on the left side, the opposite side. of the one i shimmed. It is about .015" . I think it would be worth it in the near future to remove column and clean that paint off after seeing how the z saddle and head reacted to having nice slclean surfaces free of paint.
 
Milling wood is a good first test.

I think I mentioned it before, but WRT to shimming the column, you may want to also look at @ptrotter posts again. He took his completely apart before stripping and repainting, but I do not recall if he provided any insight to shimming the column. I know he had too and he works hard to get things lined up right. He also said that he found shims when he took it apart, but I don't think he kept them. Maybe they were no good after coming apart.

Good luck.

Dave
 
I put a square on the table to test the squareness of xy and im not getting variation of over .0005" along 6" so I'm going to call that good.

So far ive used an 3/8 endmill on some 6061 and some cold rolled steel with very good results. Did a little drilling in the steel as well and that went well too.

At this point im pretty happy with the machine. I think my initial misalignment/excess movement when locking the gibs on the Z was due to the gib being very touchy as well as well as the paint that had gathered on some of the mating surfaces. Partially my fault i suppose.

My only issue at this point is the head will kind of slip a bit when traveling at the bottom of the z. Its really in a spot that ill most like never be milling but im going to have to figure that out. Will look into it more asap. Not sure its even a repeatable issue just something i noticed once.

Overall im quite thrilled with the machine. Even if i did have to take it apart and clean it. I knew i was going to want to do that anyways. I hopr this all holds up. Should translate to some pretty flat and square cuts :)
 
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