Another Marvel of Chinese manufacturing

[Fancy]

Was trying BK 12 Blocks and when tightening the nut it's either too lose and the screw has forward/backward play or it's too tight and the screw can't rotate :(

[m_c]

Dismantle the block and check everything is assembled the correct way.

There is history of these being assembled wrong, which gives the symptoms you've described.

[Fancy]

Did just that and all i see is just two bearings back to back.

[Clive S]

Did just that and all i see is just two bearings back to back.

There should be spacers tubes at each end as well.

[Fancy]

should i adjust the nut to have minimum drag ? or do i tighten all the way and it should be fine ? if i should tighten all the way then the block is faulty. please clarify this point for me as all my knowledge is theoretical from forums and such.

[Clive S]

should i adjust the nut to have minimum drag ? or do i tighten all the way and it should be fine ? if i should tighten all the way then the block is faulty. please clarify this point for me as all my knowledge is theoretical from forums and such.

You haven't answered the last statement ie. are there spacer tubes in the block. Also are the bearings AC type or standard ball bearings

[Fancy]

I didn't answer because I said in a previous reply that i disassembled them and there are only two bearings inside. I don't know what an AC type bearing is, Would you explain ? Thanks.

[Clive S]

I didn't answer because I said in a previous reply that i disassembled them and there are only two bearings inside. I don't know what an AC type bearing is, Would you explain ? Thanks.

There should be spacer tubes either side of the bearings.. A picture of the parts would help. Is there a number on the bearing to identify it and is there an oil seal. AC bearings (which they should be) have to be fitted back to back.

Where did you get them from?

[Fancy]

The bearings indeed have a writing on them it is 5001Z. I got BK and FK Blocks and neither are working. I got them from a local seller.

[Clive S]

The bearings indeed have a writing on them it is 5001Z. I got BK and FK Blocks and neither are working. I got them from a local seller.

Those are not BK blocks, BK are like this :- https://www.google.com/search?safe=a...V6WUHewkEU1-M:

AC bearings a bit like these:- https://simplybearings.co.uk/shop/p8...duct_info.html

5001Z bearings are not good for ball screws you might be able to get the AC type and fit them back to back.

Your blocks are FK and FF:- https://www.google.com/search?safe=a...8ASwh55BuW4nM:

Looking at your housing is there a spacer tube in the bearing seal? Look at the picture of the BK block above you can see a spacer at each side