[binfordw]

Curious,

I'm thinking about replacing my X and Y ballscrews with new. I currently have .008" of backlash on both axis... My Y axis tends to struggle to maintain .008, as it still uses a generic thrust washer fixed mount setup. I have a grizzly G0463 that I converted to cnc years back, with a sorta cheap ballscrew/mount kit.

Recent changes to my Z axis ballscrew mount bearings made the mill run far better, but now I'm getting greedy I guess and want to go further.



I am looking to buy some C7 screws from automation overstock Such as -- https://www.automation-overstock.com...05%2D0350%2DFS


Any thoughts on this? They claim less that .0006" backlash on these, which would be amazing for my setup. Which pitch, 5mm or 10mm?

I've considered buying linear rails as well and doing new ballscrews and machining off the dovetails and adding rails, but just doing new screws would be easier. Not sure how much improvement I could really see from rails.

[binfordw]

Man, just not much action here.

Anyway, I ordered a new X and Y ballscrew from the link I posted, with matching support bearings, ballnut mounts and motor couplings. Might take a bit of fiddling to get them installed, but I should be able to use the old screw setup to machine parts if needed to get them mounted. Interested to see if my backlash drops below .001" after I get them installed.

- - - Updated - - -

Man, just not much action here.

Anyway, I ordered a new X and Y ballscrew from the link I posted, with matching support bearings, ballnut mounts and motor couplings. Might take a bit of fiddling to get them installed, but I should be able to use the old screw setup to machine parts if needed to get them mounted. Interested to see if my backlash drops below .001" after I get them installed.

[ninefinger]

This forum (don't know about the rest of the site) just dropped in participation last few years. I make it back in here once in a while but not more than probably 2 times a month.
I'm in similar position regarding backlash, but just don't use my machine enough to warrant doing anything about it. I'll be interested to see how yours perform for you.

[Azalin]

In my BF20L mill I ended up using double ball nuts because the backlash of my old single ones (Chinese) was terrible. I still have backlash but in acceptable range I believe.

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[Azalin]

By the way check the bearings in that BK end support. They use deep groove ball bearings instead of angular contact ball bearings.

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[binfordw]

These are called out as angular contact bearings, so we will see.

The C7 screws have a spec'd single nut backlash rating of <.0006". Excited to see the results after I get them installed.

[Azalin]

By "them" I meant the Chinese. I don't know the if one in your link is made in China or somewhere else. Just a little heads up.

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[atomarc]

Any ball screw of hobby size made in China will be a rolled screw, and I'm very doubtful that with a single ball nut, the backlash could be anywhere near 6 tenths. Any screw with double nuts can be adjusted to almost zero backlash, cheap rolled screws or others. All this is predicated on the fact that the fixed end of the screw is firmly held in some bearing arrangement that also allows zero backlash. This has been my experience anyway.

[binfordw]

These are not “Chinese” screws as far as I’m aware. They atleast have listed tolerances/specs and are sold by a reputable company here in the states, so if they wind up being far worse than the .0006” max that is called out on the specs, I’ll be giving them a call.

This is the reason I paid more to avoid the Chinese ones that don’t list specs, so I would know what I was getting.


We will see!

[Azalin]

I wasn't referring to the ball screw. I was referring to the bearings inside the BK end support.

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[atomarc]

The ball screw you linked in the original post is most certifiably a Chinese unit, a clone of hundreds of other floating around the net. This is not to say you can't get respectable backlash with this unit, but unless you re-ball the nut with larger balls, or double-nut the assembly, the stated 6 tenths backlash is a pipe dream. Utilizing a double ball nut setup is perfectly acceptable and is used on many high end, high precision machine tools.

[binfordw]

Well, hopefully some of the older, more experienced Chinese kids put these together then

It does say they are individually loaded. I'll be disappointed if these do not drastically improve the backlash in my XY. I'm really hoping for them to be what the specs say and get my backlash low enough to not need to compensate for it in Mach.

[atomarc]

Yes..hope for experienced kids on the assembly line (floor).:banana:

I hadn't noticed the note in the description of the ball screw about each nut being individually loaded for that particular screw. As I mentioned above, that is a method of attaining better backlash, so the touted 6 tenths might be accurate. Dave at Arizona Video sold, or sells, ball screw setups and offers the service of re-balling the nuts to achieve better accuracy. I did a G0704 CNC conversion, and Dave re-balled all the ball nuts AND straightened the 'not so straight' ball screw, which wasn't even purchased from him for the tidy sum of..GRATIS. A great guy!

[binfordw]

Well I finished up the install today,

I had to disassemble the mill 3X times to check fitment, and them reassemble to mill the new parts. I had the cut down the flanges on both ballscrew nuts to get them to fit, otherwise it went fairly well.

I now have less than .001" backlash on both X and Y. I did a test cut of a 1" bore, and it looks great. No visible sign of the lead-in/out (!), and it measures about as concentric as I could expect to check with calipers. Excited to try more parts to see how the quality goes.


Super happy with these parts!

[smokey41]

Have you done anymore testing to see how the new ball screws are doing?
Thanks

[binfordw]

They are doing great. I did have some backlash return- but turns out I had bolts come loose.