[1875]

I forgot to mention the grease I have, it is Mobile MLUX EP1

And which grease would be right for the spindle bearings if I go there?

Thanks

[mactec54]

1875

It seems you did not understand what I said about the return tubes on the Ball Nut this is were you should of removed the first set of balls from, this way you would of known how to reassemble the Balls they have the 2 different sizes for a reason, this is how they get Zero backlash, the NSK was one of the best Ballscrews, that Bridgeport used, & the most expensive, around $1200 just for that Ballscrew

The spindle & bearings as I said are removed from the front of the Quill, there is no other way to remove the spindle, & the nut you see at the top, comes out the front as part of the assembly, the correct Grease you should be using is called Kluber NBU 15, this is what you should be using for all the Bearings that you need to put grease in, you also need to put the correct, measured amount of grease in the bearings to much is not a good thing

[1875]

Thanks, mactec54.

When I took the tube out, there were balls of two sizes that came with it, same as the loose ones. I suspect the balls alternate, and the first and last are the larger size, but I will have to measure them all and see what I have. I'll also have to assume that I have all the balls and use that many when figuring out how to reassemble. Thanks.

[1875]

Now I'm looking for the grade and material of ball for this ball screw? Tolerance or spec of the ball I need for the replacements.

[mactec54]

Thanks, mactec54.

When I took the tube out, there were balls of two sizes that came with it, same as the loose ones. I suspect the balls alternate, and the first and last are the larger size, but I will have to measure them all and see what I have. I'll also have to assume that I have all the balls and use that many when figuring out how to reassemble. Thanks.

That is why I said to remove the return tube, the bottom row most likely would of had a full set, this would of given you how many & what size they were, the material will be the chrome steel, the grade anything from a grade 25 up will do

[1875]

OK, well I figured that.

Now I will use some grease and load up the screw and tube (without the nut) and see if it comes out right.

I suspect that the balls are actually 0.1250 and 0.1240.

An ebay vendor has 0.1250 and either 0.1237 or 0.1242. For the small ball, would it be better under or slightly over sized?

[mactec54]

1875

You won't get good quality balls from any Ebay sales that would be suitable for your ballscrew,unless they are a Ballscrew rebuild company, you need to get them from the links/companys that you posted

[1875]

Thanks mactec54. I'm not sure I know what I need to order. I could install the balls I have and only be the worse for wear.

After recounting I found 290 balls total, which would be 145 for each circuit, and a large balls adjacent in each circuit, which is not what I expected. Now I'm lost.

[mactec54]

1875

What size is the large balls, they won't be more than .001 difference in the 2 sizes, there also won't be much wear on the Balls, so what ever size they measure they will be within a .0001 of that size, some times they are loaded 2 small 1 big I have seen them have also 3 small then 1 big, so you will have to see how they work out, there will also be a gap when circut is full, the balls won't work out exact, or be tight together when full

You did say some of the ball are damaged, you have it apart the old balls will damage the screw if left as they are, send some big & small balls to the link you posted, & ask them to size them for you

[1875]

OK on the balls.

Back to the grease. I think the expensive spindle grease is not really needed in these large ball screw carriers? I'm wondering if the Mobilux EP1 or Mobilegrease 28 would be OK, or someone suggested MYSTIK JT6 EP2.

I've looked at the specs and it seems the mobilux has the best wear scar test data (0.4), but the JT6 seems to have the best all around specs, but I'm not knowlable on grease or implications in this application.

Mobilux? EP 0, 1, 2, 3, 460, 004 and 023

Mobilgrease 28

http://www.docs.citgo.com/msds_pi/591094.pdf

Or something else?

[mactec54]

1875

They are the same type of precision Bearings as what is in the spindle,they should be treated the same way, But it is your machine so you can use what ever you think will work, for you

[1875]

Well, I do want to get what is necessary. Since these bearings are large, I ordered the 14oz tube and will probably use it on my lathe spindle bearings too. Do you know how much should go in each of the large carrier bearings here? Thanks.

[mactec54]

1875

The grease fill can very a little around 30% is a good number, so really not much is needed, some formulas below is a guide that will give you enough without over doing it,
the amount you got will last a very long time, you may want to change it for a smaller quantity, using a syringe is a good/best way to put the grease into the bearings

G = 0.005 x DB

where,
G = grease quantity in grams
D = bearing outside diameter in mm
B = total bearing width in mm

[1875]

Thanks mactec. It's hard for me to relate a weight to volume. I did see the 50g tube, but thought that might not be enough for these large bearings, and especially if I were to do the spindle. It seemed like I took quite a bit out when cleaning.

I think exchanges are impossible nowadays unless one is willing to burn up quite a bit in shipping things back and forth, and risking just loosing out entirely as there is no positive connection at the other end. So far I have $150 of grease in the mail and nobody is responding to cancelling orders. I just seem to keep stepping in potholes along the way here.

At any rate, from the formula it appears that about 1/2 of the 50g tube would have been enough for these two bearings. I'll look for a syringe and ensure I get the grease in where it belongs. Thanks for the tip.

[1875]

Just a quick update.

I got the z-axis ball screw back together, 160 balls in each of the two circuits (80 big and 80 small). That means I was missing 30 balls in addition to the 36 balls I found sitting on top of the screw. Who knows what could have happened in the past with this as I did not find any more balls floating around in the head - maybe someone removed the quill entirely and learned about the balls, and then tried to put it back together...? Now it seems to be back in order and ready to go.

I do have a question about the lock rings for the ball screw and back gear carrier bearings. They did not seem all that tight when I got them off, but is the torque important on either of these?

[mactec54]

I do have a question about the lock rings for the ball screw and back gear carrier bearings. They did not seem all that tight when I got them off, but is the torque important on either of these?

Do you have the nylock nuts, or is there locking washer's with tabs, just do them up as tight as you can, the Bearings are matched pairs so you can not over tighten them, if they are the nylock type lock-nuts, you should replace them, it is important to have the lock-nuts done up tight, if not you will have backlash, which you don't want to have

[1875]

Thanks mactec. The Z ball screw carrier bearings do have a tabbed lock washer. The back gear nut did not have this.

[1875]

I now have the head completely apart and finished most of the sanding prep for paint. I took the spindle out of the quill and started removing the bearings. I got the lock collar off and the single bearing off, but the spindle bearings are requiring some force and I want to make sure I'm doing it right.

I am using a 20 ton press. The nose collar is on the spindle and it will not come off the tool end, so looks like it must press off with the bearings up the spindle shaft. I was planning to block under the spindle nose collar and press the spindle shaft down. I expect the bearings with the nose collar to all be able to press off together. I just don't know if there is a step or something for the nose collar to get caught on. I have not pressed very hard and I did not want to overload the spindle and have it buckle, plus I want to clean and reuse the spindle bearings if they look good under the microscope.

I have it soaking in penetrating oil, so do I just need more force to press the whole mess off?

[mactec54]

1875

If the Bearings are that tight, then you will damage them getting it apart, these are angular contact Bearings,(that will be mounted Back to Back) you will be pressing on the outside of the Bearing, That is why I said in other posts, that if you don't have to do them , leave them, until they need replacing

When they are tight, the top bearing will come off, & most times the bottom bearing will come apart, this will leave the inner bearing race still on the spindle

When pressing on the bearings like this, the top bearing's balls will be pushing into the bearing race, this is were/when the damage will happen

The replacement of a new set of Bearings are needed, they are a matched pair, which are spendy

[1875]

Thanks Mactec. I could tell where the force was being transmitted and that is why I did not want to press hard.The penetrating oil must have soaked in because last night I did not have to press hard to get a little pop, they creaked right off.

I popped off the seals and cleaned them out. with WD they run smooth, so I'll re-pack and see how they go. Any tip on where to get a good pair if I need them?