rm1605/bk/bf12 ballscrew questions

[frige]

I few ballscrew questions...

1) I assume this is the way it goes together? Can I flip the bk12 around?
2) When I load it, is the tension between A-B? It doesnt spin as freely as I would expect. Between A-C, the bearing would slide in the housing.
3) I have a coupler with a set screw - should I file a flat spot on the shaft?
4) Any MDF construction mounting suggestions?

-johnny

[Connor9220]

Originally Posted by frige I few ballscrew questions... 1) I assume this is the way it goes together? Can I flip the bk12 around? 2) When I load it, is the tension between A-B? It doesnt spin as freely as I would expect. Between A-C, the bearing would slide in the housing. 3) I have a coupler with a set screw - should I file a flat spot on the shaft? 4) Any MDF construction mounting suggestions? -johnny

You get that from liearmotionbearings on ebay? I had issues with the Jam nut binding against the rubber gadget... The bearing colliers they provided were not long enough.. I had someone make me some longer ones, and that fixed the issue. The C side is free-floating.. just to keep your screw from flapping in the breeze.

Thanks, Connor

[frige]

yes - got them from linearmotionbearigs on ebay. Same problem.
I'll have to figure something out.

[APinSoFla]

If you have not done so, I'm going to suggest that you disassemble the BK bearing block and clean/grease the bearings and seals. There was a lot of debris in the BK blocks I got and not a single drop of lubricant. If you decide to do this, please note: The front bearing retainer plate with the 4 small socket cap screws is laid out by hand and is probably not interchangeable with any other BK block. Mine would only go back together in a single orientation due to the holes being inconsistently spaced.

Further, it was only upon disassembly that I found that the seals were what was causing the assembly to appear to be reasonably tight as far as backlash. Once the seals were removed a lot of slop appeared. After a bunch of measurements, it turned out that the bearing holes in both blocks were bored too deep (one of them was +0.07X"...yikes). Luckily I had access to a lathe and was able to turn some thin spacers that were installed between the bearings to take up the space and add a slight amount of preload to the bearings.

As for your specific questions:
1. You are correct. yes.
2. Yes. See above. Yes, it's supposed to slide in order to allow for linear expansion of the screw.
3. Can't hurt.
4. Without knowing what your design is like, it's kind of difficult to say.

[clockworkgear]

I see you guys have also puchased from linearmotionbearings on ebay.

Couple of questions:

How long did you have to wait for the product to arrive?

Have you guys seen any threads here that have pictures/diagrams/CAD files of how those particular components were put together to create a machine?

Many thanks,

Patrick

[frige]

Once the Chinese new year was over, it took 6 days to get my order.

I have not found any CAD files or specific plans.

I have run across a few threads though...
http://www.cnczone.com/forums/open_s...uild_free.html
http://www.cnczone.com/forums/cnc_wo...-_proto-m.html
http://www.cnczone.com/forums/diy-cn...r_1x0_7x0.html

About the bk12:
I think I will order some sleeve bearings (12mm inside 14mm outside) from mcmaster and cut them to size.
-johnny

[hemsworthlad]

I buy lots of Ballscrews and BK/BF blocks from Chai @ Linearmotion and the sticking is caused not by the collars being too short but more because the seals are not inserted far enough into the body and the lock nut rubs against the seal or the screw on the backside rubs on the seal.
It's a pain in the arse but a simple fix by using a piece of tube the same as the seal outer Dia and inserting in a press or vice lightly tightening to push evenly deeper into housing. Thou be carefull not to push too far so they make contact with the bearing.

To the person who asked about times, It takes between 9 & 12 days from initial order to arrival here in UK, more often than not it's 9 days.!
I've just had a spindle delivered and it arrived in 5 days, the service is excellent and Chai a great guy to deal with.
The quality is OK concidering the low price and more than good enough for serious hobby use.

[Pplug]

Originally Posted by frige Once the Chinese new year was over, it took 6 days to get my order. I have not found any CAD files or specific plans. I have run across a few threads though... http://www.cnczone.com/forums/open_s...uild_free.html http://www.cnczone.com/forums/cnc_wo...-_proto-m.html http://www.cnczone.com/forums/diy-cn...r_1x0_7x0.html About the bk12: I think I will order some sleeve bearings (12mm inside 14mm outside) from mcmaster and cut them to size. -johnny

I ordered some shim washers for mine to go in between the two bearings centers to lightly preloaded them. I also purchased shims to pad just the outsides of the bearings against the block. The shims were only .2mm in size and I only needed one or two per block. 8 months later and still working great!