Need Help!- Bearings + Shafts

[pippin88]

Just received my bearings from Chai (linearmotionbearings2008) to match my ballscrews.

Having a few little problems:
1. I can't get one of the BK12 (dual angular contact bearing blocks) onto any of my ballscrews, the other 2 BK12's work fine. The issue seems to be the angular bearing closer to the flat face is simply too small. I've tried sanding the shaft of one of the ballscrews a little, but I don't want to sand too much. The other bearing in the block seems to slip over ok.
2. I can't get any of the BF12s on properly, and I managed to get them all on a bit and now can't get them off!!! Any tips on how to get them off without damaging anything?

I'm a little annoyed really as I also didn't receive any locknuts and the bearing blocks were delayed too (omitted from my original shipment)

Help is appreciated!

[dfmiller]

Sounds like you are running into some tolerancing issues. Too bad everything was not shipped at once.
That's a pain.
I was pleased with the leadscrews and nuts I got from him.
He seems to have a pretty good reputation for fixing things. Have you contacted him?

Please keep us updated on how this works out.
A small gear puller should help. Hammering is not a good idea. If you have some threaded rod, some scraps of metal and some ingenuity you can make a puller. Or pusher.

Best of luck.
Dave

[louieatienza]

Originally Posted by pippin88 Just received my bearings from Chai (linearmotionbearings2008) to match my ballscrews. Having a few little problems: 1. I can't get one of the BK12 (dual angular contact bearing blocks) onto any of my ballscrews, the other 2 BK12's work fine. The issue seems to be the angular bearing closer to the flat face is simply too small. I've tried sanding the shaft of one of the ballscrews a little, but I don't want to sand too much. The other bearing in the block seems to slip over ok. 2. I can't get any of the BF12s on properly, and I managed to get them all on a bit and now can't get them off!!! Any tips on how to get them off without damaging anything? I'm a little annoyed really as I also didn't receive any locknuts and the bearing blocks were delayed too (omitted from my original shipment) Help is appreciated!

You should be able to find a cheap-o gear puller at an auto parts store that would work fine.

I will say, you aren't the only one that has had these issues. I've had a couple with the ones I'vev ordered, and decided to buy higher quality (and consequently more expensive) fixed and free end blocks, that are a perfect slip fit on my ballscrews (slide in like a piston).

It's possible there's a problem with his bearing source? Maybe a bearing swap is in order?

[pippin88]

Got a reply from Chai, which I presume results from slight language miscommunication

Originally Posted by sent by pippin88 The problem with the BK12 appears to be the angular bearing closer to the flat face is simply too small. The other bearing in the block seems to slip over ok. I've tried sanding the shaft of one of the ballscrews a little, but I don't want to sand too much. If I sand the ballscrew down to fit the smaller bearing I think the other bearing in the block will not hold the shaft securely.

Originally Posted by chai's reply The bearing mounts should not be mounted to the machned ends. If so the precision will be lost. Please Don't make to much treament for the ends. You can press the bearing to its proper place with a little presure machine. Thanks Chai

Grrr

[pippin88]

Thanks for the suggestions guys. Local autoshop and decent tool shop didn't have anything to suit (all bearing pullers were big and designed to pull from the outer race and couldn't deal with the BF12 housing).

Got them off just then by a few gentle taps on the end of the shaft through an appropriately sized bolt while holding onto the BF12. They were only put on by hand so weren't on *that* hard.
I'll be doing a light sand before I put them on again.

The problem with the BK12 remains. Waiting to hear back from Chai further.

Did get my MDF mostly cut to size today. Tomorrow will go grab some aluminium.

[Walky]

I used very fine sand paper with lubricant to reduce the diameter and it became a nice fit, you just need to sand evenly.

Check if there is any backlash on your block, you might have to add some shims between the angular contact bearings if there's no (or not enough) preload.

Get a rubber hammer, those things are very handy to press stuff without damage.


Just thought I'd add some general tips I think will help some of you improve communication with Chai:


- Be simple, but specific.

- Try to use the same words he uses, so you can be sure you're talking about the same thing.

- If possible, ask one question at a time. I'm sure he must answer a LOT of mail daily, so it might be hard for him to keep track of all of it if yours are too long or too many. If I ask four questions at a time I usually get one or two answers, but if I time each email so he can answer them before asking my next question, I get an answer for everything. If for some reason you don't get a reply sometime, just send a new mail.

- If you can send a picture or drawing to make your idea clearer, do it.

- Ask for the tracking number (if available) if you didn't get one.

- Of course, be polite.

- Use relatively simple, "to the point" english. Don't get me wrong, Chai's english is great, but too many (or complex) words and it's easy to lose the main idea or misinterpret it. Remember that chinese is a very different language than english and has a different thought structure, so the cleaner the idea is, the better.



Funny language-related story: Once I tried to politely decline a japanese's teacher invitation to her home by saying it in japanese. Instead of saying "I won't be able to go to your house" I accidentally swapped one letter and started with "Me, on top of you..."; you can imagine the look on her face

[louieatienza]

Check out this thread for more info on "tuning up" Chai's bearing blocks....

http://www.cnczone.com/forums/vertic...tml#post983405

[pippin88]

Thanks Walky and louie.

Chai is sending me the locknuts and two replacement bearings to go in the non-fitting BK12.

I'm away for work for a couple of weeks, so hasn't caused a major inconvenience. Can't fault Chai on responding quickly to messages and his communication is in general quite good, but the bearings were missed from my shipment and then they managed to omit the locknuts and give me a dodgy bearing which was quite frustrating.

[pippin88]

Well, I got my bearings an lock nuts from Chai, and of course the locknuts rub on the oil seals (as do the ballscrews actually) the spacers/collars are simply too short (by about 1mm really). I've removed the oil seals for now until I have access to a lathe to turn some longer collars.

Pulled apart my faulty BK block:
Unscrewed face plate. Used flat head screw driver to pry oil seal out of other end. Used socket as large as possible in the hole and tightened in a vice which moved the bearings to the surface. Then a few blows with a rubber mallet on the socket popped the bearings out.



Just wanted to confirm bearing orientation before I reassemble. From what I can see on another block the text side of the bearings face out.



My plan is to slip the bearings into the housing then use the socket and vice to push them right in. Will that be ok?

Bearings:

[Velocirex]

I think you do want a reasonably tight fit for the bearings on the ballscrew to ensure the inner part of the bearing moves with the screw. The fit is supposed to be a js6 which is "Fitting which accommodates a light gap. Precision fitting which locks both parts while the unit is used. Fitting which allows assembling and disassembling with a wooden or lead hammer."

You should not have to press them on, but some light raps with a rubber mallet is ok and expected. If they go on like a piston in a cylinder, I'd be a little concerned that they're too loose. You don't want them so loose that you can easily pull them off with one hand. I think thats why Chai is recommending to take it easy with working the machined surfaces.

Similarly, if the seals don't touch the shaft they can't seal.

[leaveme]

Hi pippin88,

Are you using Angular contact bearing at both side of the ballscrew?
Using angular contact bearing at motor side is ideal and standard radial bearing should be used on other side.