Can't Win Some Days

I'm learning a lot... like you hardly need any torque on the thrust bearing retaining nut on this KMB1. I learned how to make new tab lock
washers too since nobody stocks them, but several say they can get them... eventually. I even learned what the X axis is supposed to sound like with good thrust bearings. It never really had any problems, but its sure sounds a lot smoother now. Obviously the bearings were bad.
With new thrust bearings on the Y-Axis its pretty smooth now too, but only for about 7/10 of a turn. Then it pulses. Its actually a lot worse than it was before. Before I could see a little flutter about every 1000 steps or so on the scope, but the machine appeared to move smoothly. I guess the Y-axis thrust bearings were so wore out that it allowed it to move smoother. With new fresh bearings it pulses badly. And no its not a matter of tuning. As near as I can tell the ballscrew is bent and its binding as it turns. That would sure explain the chatter I saw before. Now its unusable.
The bad part is I don't know how to remove the new bearings and save them. The obvious way to pull the bearings pulls the rear bearing apart when you take the housing and bearings off the shaft. So... even if I find a good replacement ballscrew I'll wind up having to chase down another set of bearings too.
Of course I have one piece to make to finish a job that is just a little too big for the little mills.
DANG-IT!
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On 1/14/2018 1:25 PM, Bob La Londe wrote:






I've got some much smaller cheap Chinese double nut ball screws on the shelf. I'm right at that point where I am tempted to make an adapter plate to mount the ball nut for one of those, and make my own bearing and motor mounting plate for the front of the machine. It probably wouldn't last long, but it should be reversible. I'd have to direct drive the screw which would leave the motor sticking out in the way in the front of the machine. Its not a pleasant solution. Atleast I could make all the parts on the little high speed machines, and then I might be able to finish my current job.
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On 01/14/2018 02:25 PM, Bob La Londe wrote:
If you're going to junk the old ballscrew anyway, just machine away enough to let you get the good bearings off.
--
Bob Nichols AT comcast.net I am "RNichols42"

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On 1/14/2018 9:11 PM, Robert Nichols wrote: > On 01/14/2018 02:25 PM, Bob La Londe wrote: >> The bad part is I don't know how to remove the new bearings and save them. The obvious way to pull the bearings pulls the rear bearing apart when you take the housing and bearings off the shaft. So... even if I find a good replacement ballscrew I'll wind up having to chase down another set of bearings too. > > If you're going to junk the old ballscrew anyway, just machine away enough to let you get the good bearings off. >
That's not a bad idea. Although I also considered turning the bearing surface to a smaller more concentric OD and using a bushing. Probably would re-turn the whole end and make appropriate adjustments including a different size encoder disc though... or a whole bunch of bushings. LOL.
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On 1/15/2018 9:57 AM, Gunner Asch wrote:
> wrote: > >> I'm learning a lot... like you hardly need any torque on the thrust >> bearing retaining nut on this KMB1. I learned how to make new tab lock >> washers too since nobody stocks them, but several say they can get >> them... eventually. I even learned what the X axis is supposed to sound >> like with good thrust bearings. It never really had any problems, but >> its sure sounds a lot smoother now. Obviously the bearings were bad. >> >> With new thrust bearings on the Y-Axis its pretty smooth now too, but >> only for about 7/10 of a turn. Then it pulses. Its actually a lot >> worse than it was before. Before I could see a little flutter about >> every 1000 steps or so on the scope, but the machine appeared to move >> smoothly. I guess the Y-axis thrust bearings were so wore out that it >> allowed it to move smoother. With new fresh bearings it pulses badly. >> And no its not a matter of tuning. As near as I can tell the ballscrew >> is bent and its binding as it turns. That would sure explain the >> chatter I saw before. Now its unusable. >> >> The bad part is I don't know how to remove the new bearings and save >> them. The obvious way to pull the bearings pulls the rear bearing apart >> when you take the housing and bearings off the shaft. So... even if I >> find a good replacement ballscrew I'll wind up having to chase down >> another set of bearings too. >> >> Of course I have one piece to make to finish a job that is just a little >> too big for the little mills. >> >> DANG-IT! > > Dont dispair quite yet...ballscrews can..can be found cheaply enough > both on Ebay and other locations. > > http://www.practicalmachinist.com/vb/general/looking-cheap-ball-screws-232777/ > > https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR12.TRC2.A0.H0.Xballscrews.TRS0&_nkw Ίllscrews&_sacat=0 > > > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus >
Yep. Lots of options. I'll look at some of the sources on the PM thread with more care in a bit.
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On 1/15/2018 10:58 AM, Gunner Asch wrote:

I'll post some info when I have time to pull that part of the machine apart again. Right now I have to get some jobs on the little machines and keep them going. Might not be until tonight or tomorrow when I some have time to disassemble.
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On 1/15/2018 11:28 AM, Bob La Londe wrote:






Basic Dimensions:
http://www.cncmoldsnstuff.com/ballscrew/20180118_183807.jpg
More Pictures: http://www.cncmoldsnstuff.com/ballscrew
Good news. I was able to get the ball screw out of the new bearings without pulling the bearings apart. I unbolted everything from the machine and took it out as an assembly. Without everything in a bind it came apart modestly easily.
If something wonderful doesn't present itself I'll have a go at turning the end of the shaft down and using a bushing or bushings to bring it back up to spec. Obviously I'd have to change threads and nuts, but that's not a huge problem I suspect.
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On 1/18/2018 7:19 PM, Bob La Londe wrote:








Nothing Huh? Ok, well I need the machine working. I can get a decent price on a metric screw with oversized balls new from Automation Overstock. (about 7 tenths backlash) I'll just go that way and make an adapter, because I need to get the machine going pretty quickly. its been down for three weeks, and while it doesn't do the bulk of my work its made me realize how much I do use it. There are somethings that are easier to do with horsepower than with high speed and feed.
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On 1/23/2018 2:21 AM, Gunner Asch wrote:








Well in the years we have interacted on-line this is the fifth time you haven't followed through on something you said you would do for me. The first time I think was before your stroke so call it 4 times. One in theory you might still be following thru on so still 3 times. As to the tolerance... well... if you had something better I could afford and followed through I'd have bought it. But go ahead and blink feigning astonishment and superiority. It doesn't matter to me how superior you think you are in everything you are or do or have. Does me no good without follow through. I just need to get my job done. With or without you.
I have seen others post about how you did something or sent them something so I just figured you didn't like me, and didn't mind wasting my time.
You do know the original claim of tolerance for this machine in the manual is only .003, although its always produced better than .001 for me. Its got a decent screw, but its still only a single nut ball nut.
So, why in the heck do you think I posted dimensions and images at your request if I had it all fixed. <<<<--- Note the lack of a question mark. That's on purpose.
Have a good life. I have work to do.
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On 1/24/2018 4:26 AM, Gunner Asch wrote:






******************** Here ***********************

*************************************************


**** Apart without breaking doesn't mean fixed ****


**** Sure doesn't sound like fixed there either. Sounds like waiting and hoping for a better option ****

Don't worry about it. I didn't think you would come through anyway. I just gave you the benefit of the doubt one more time since it didn't really cost me anything, and I generated those pics for somebody else anyway.
Have a great life. I need to get back to work.
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