sqt10 ballscrew thrust bearings

After getting the correct bearings in for my machine I went to put them in and I got a bit blind sided by the nut for creating preload on the bearings. It is a SFK KMT5 :
http://www.ondrives.com/pdf/rino/catalogue/bearings/B_Lock_Nuts.pdf

I removed the set screws, but I can't crack this nut. I am gonna let is sit with some penetrant over night and come back to it tomorrow or Monday. I have never dealt with these style nuts before and I am wondering if the threaded inserts under the set screws need to come out before this will crack loose? I can't really see why but this thing is really cranked on there.

I am currently using a regular spanner and there is very little room to get any leverage on it, I am worried I am going to damage the nut. I am wondering if I should make a socket to crank on it but it doesn;t seem this should be necessary for a preload nut... Maybe some Monkey has been in here before?

The housing:


The Nut:


Limited access:

some of those have double set screws. if not Hammer and chisel/punch it out. most of the time one or two hits will knock it loose. should not damage the nut

Justin_Terry said:

some of those have double set screws. if not Hammer and chisel/punch it out. most of the time one or two hits will knock it loose. should not damage the nut

Click to expand...

You mean two set screws in the same hole? This nut had either 3 set screws radially, one per hole. I can see the brass thread lock in the bottom of each set screw hole. I am wondering if these things sometimes get stuck on the shaft especially if they are over tightened?

I think you are probably right about giving it a wack with a chisel and hammer, likely a better solution for breaking it loose then torquing on it with a spanner...

Dave Cross said:

I think you are probably right about giving it a wack with a chisel and hammer, likely a better solution for breaking it loose then torquing on it with a spanner...

Click to expand...

A dull air chisel in an air hammer is just the ticket in close quarters like that. It takes surprising very little effort to get a nut to turn so feather the throttle gently..

you mean those slots are for a spanner?
couple good smacks and your back to work
i put them on that tight too.
you want -0- endplay on that screw

Dave,

If necessary, you can get better access by loosening the big Z-axis sliding way cover from the carriage and push the cover all the way back towards the headstock. Then you can work from the front side of the machine...standing in the "hole" where the coolant tank and chip conveyor go.

I agree with the others, a blunt-end chisel or punch, and a machinist hammer are the tools to loosen/tighten the preload nut.

This thread reminds me, I got to do a Z-axis thrust bearing replace on my old trusty QT10N...

Greg

Wippin, I knocked the nut off with a chisel and hammer, but man was that thing cranked, I was getting worried I was going wreck the nut before it was cracked loose. Why do you crank them so tight? Doesn't that just prematurely wear out the bearings? I was taught to tighten them up so that full contact is made, back the nut off and then bring it back up again but just until full contact is made, not actually torquing on them.

Greg, unfortunately the Z axis cover does not go far enough back, well it would if I wanted to remove a ton of stuff, and pulling it straight out would be a problem because there is a column support for the gantry in the way as well. At least I have the correct bearings and can put this thing back together now. The Z axis is a pretty quick and simple job. The X axis does not look so inviting, I think I have to remove the mill motor and support to get at the coupling for the encoder, and also slide the turret all the way down X-, still not sure what the safest way of doing that is.

The orange casting is the bracket for the mill motor:


Here you can see the X axis ways, the encoder, and the need to slide the turret down to gain any access:


Encoder:


From the other side:

I'm thinkin' that my Hardinges have some of those nuts that have self lockers. ???

But I kant imagine balling on it to tighten agginst the bearings THAT hard. ???

It appears that I got the Z's that we did on one machine a yr or two ago too tight, and we Shirley didn't ball on them that hard, and they are squaking now.

I jist kant see balling on them too hard either. ???



--------------

Think Snow Eh!
Ox

Remember when we would "stretch" and "squeeze" a screw to make the pitch error correct Wip? Talk about tight nuts...........

Leelund said:

Remember when we would "stretch" and "squeeze" a screw to make the pitch error correct Wip? Talk about tight nuts...........

Click to expand...

Is that common practise when you have a lead screw with angular contact bearings on one end and a roller on the other? I'm not digging the Z axis leadscrew assembly on this machine at all.

one way they can get that tight is if over time someone has been retightening them to recover lost motion from wear.
they do not need to be THAT tight, but real snug is a good thing, great grease is another.
that setup is on a whole lot of mazaks and it holds up well.
if i had to describe the "torque spec" it would be 2 lb smacks with a 10 oz. ball pean untill you get 2 smacks in a row that have the same pitch. thats tight, but not as rude as they were when you took them off.
can you get a picture of the mechanical drawing on that -x- screw so we can look at it?
alot of times there is an "access cover" down at the bottom that you can get off which then means there is no real disassemble at the the top (assuming the top are simple ball roller 6### somethings which can rest peacfully as they are, which imho can if there not squeelin')they have little to do with machinability and mostly just hold the screw in a straight line, which infact on that subject, when you are tightening these things down you want the ball screw nut as close to the end you are tightening as possible to help get screw as straight as possible.you just crank the screw by hand to get saddle to which ever end you are working on. this would be one hunch/suspect in Ox's premature failure.

Wippin, thanks for the tip on getting the nut close to the bearings when tightening them up, I hadn't thought of that and it certainly makes sense.

Here is a picture of both sides of one of the 25 TAB bearings I got for the Z axis, I was ASSuming this thing would have appropriate grease in it, do you usually add more?





I also attached a picture of the Z axis assembly just so people can see:



And here is the X axis assembly, this one looks a lot more like what I am used to, with angular contacts on both ends:

Dave.

On the box, does it say 2LR or 2NK on it any place? Those are sealed bearings you have there, no need to add grease.

Nice burnish marks on those BTW, easy to spot.

Phil.

i know this gives my true self away as being just another lazy hack maintenance man
but
for 30 years i have balanced time and money against results and been able to keep my job in a situation with no job security other than "what have you done for me lately"(over the coarse of 7 management teams i might add).
even after seeing that x drawing i would replace the bottom bearings, make sure the top are tight light newlywed pu...
and see how the thing does before tearing that whole top end apart
on a slant bed machine like those, the turrets WANT to be down from shear gravity so unless that top end is nothing but a bag of rocks i suspect that machine is gonna repeat against the bottom set.
it could also mater if you are doing some outrageously aggressive boring so you really pulling up hard on the thing.
now
if you like nothing better than a job done to it's fullest
tear the guts out of that turd
and keep us in the loop 'cause we love a good story
(times like these i shudder 'cause i know Machtool is reading this thread and i rate him as one of the true "old world machine repairmen" on this board, and I'm not sure if he will approve of such "repair frugality", sorry Phil .

kevin

Phil, yes the bearing box says "2LR/GM".

Kevin, only one end of the screw!?
I hear you on the time/vs results. The X doesn't sound too bad on this machine, and it repeats ok, so I think I will just leave it for right now and come back to it when I have a little more time. I'm absolutely the kind of person that does the job to its fullest, which often leads me into places I don't know much about

I have a job I need to run on this thing next week. I was just figuring I would do the X while I was in there, because I was already doing the Z, and I picked up a brand new X axis ballscrew for $400 (how could I say no to that?). I'll likely come back to this when I do the bearings on the sub spindle screw, but I am waiting to do that until after I get the new sub spindle way cover. Mazak wanted $4800, Hennig is doing the cover AND seals for only $650 But I have to wait 6 weeks.

I'll get this Z axis done today or tomorrow, then its on to getting the spindles and turret lined up. I could use some advice from you pro's on this.
Where should I start?

I was thinking I could use my Haimer co-ax mounted in the spindle to dial in the bore of a drill holder, and a test indicator to sweep inside the holder to get the turret square. But how do I determine if it is my spindle that really needs adjusting?

Further more, I was wondering if just mounting a fresh set of soft jaws would really be accurate enough to hold the co-ax to get the turret lined up. I guess it would be easy enough to check the run out of the co ax shaft, but then what do I do if there is run out? I can't really bore the jaws because then everything would be referenced off a potentially offset set of jaws/turret... right?

Sorry for all the green questions here guys, I really do appreciate all the advice.

Make sure you go back and check that Z nut after it's run a few hours. Had em come loose (or maybe weren't tight enough to begin with) numerous times after thrust bearing change.

Tonytn36 said:

Make sure you go back and check that Z nut after it's run a few hours. Had em come loose (or maybe weren't tight enough to begin with) numerous times after thrust bearing change.

Click to expand...

Really? With those locking inserts I would have firgured they were damn near impossible to back off, thanks for the advice I'll be checking in after a few cycles.

Tonytn36 said:

Make sure you go back and check that Z nut after it's run a few hours. Had em come loose (or maybe weren't tight enough to begin with) numerous times after thrust bearing change.

Click to expand...

X2.... I replaced thrust bearings on my HTC400... pulled the cover off a couple days later to look at the actual way cover and the nut was a touch loose on the Z axis.

But how do I determine if it is my spindle that really needs adjusting?

Click to expand...

step one is to always adjust spindle taper first
you can take a test cut even if turret is out some
because your right, if spindle is out it will give false height/radial turret readings

and of coarse if your in after the screw you would do both ends on the bearings
i hadn't notice you say you had issues with -x- i just figured you were in there have'n such a good time you couldn't stop yourself
I'm just a firm believer in "if it ain't broke don't fix it"
i am also firmly in your camp for doing everything you have time and money for.

early in my career i went deeper than i had to on something, smashed a cover in the process and lost a mission critical machine for weeks.
that only happened once.

a great guy for cover repairs is
ken even
midwest cnc services
319-610-4341
no connection just satisfied customer

Kevin, I am finally going to have time to take care of this tomorrow. Does it matter which bearing/support housing is removed? I don't see anyway I can remove the bearings without removing a housing (first time I have come across this as well, everything about these Mazaks is so strange to me).