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Fancy
13-01-2019, 03:13 PM
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
13-01-2019, 04:17 PM
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
13-01-2019, 05:56 PM
Did just that and all i see is just two bearings back to back.

Clive S
13-01-2019, 11:03 PM
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
15-01-2019, 02:50 AM
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
15-01-2019, 09:51 AM
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
15-01-2019, 12:13 PM
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
15-01-2019, 05:58 PM
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
15-01-2019, 11:17 PM
25331
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
16-01-2019, 07:56 AM
25331
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=active&biw=1904&bih=963&tbm=isch&sa=1&ei=seA-XKbUObSe1fAPs-efUA&q=bk12+bearing+blocks&oq=bk12+bearing+blocks&gs_l=img.12...38460.43290..46640...0.0..0.70.254.4 ......1....1..gws-wiz-img.eN4dm-NcyE4#imgrc=RV6WUHewkEU1-M:

AC bearings a bit like these:- https://simplybearings.co.uk/shop/p88033/Budget-7201-Single-Row-Angular-Contact-Open-Ball-Bearing-12x32x10mm/product_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=active&biw=1904&bih=963&tbm=isch&sa=1&ei=Z-A-XLfUM9PwxgOouIr4Dg&q=fk+12+bearing+blocks&oq=fk+12+bearing+blocks&gs_l=img.12...48680.49073..52249...0.0..0.106.201. 1j1......1....1..gws-wiz-img.WyeCeWp2BdQ#imgrc=s8ASwh55BuW4nM:

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

routercnc
16-01-2019, 12:45 PM
Years ago I ordered some BK bearing blocks and they did not come with the spacer tubes (2off). What happens is the ballscrew gets clamped up hard against the seals (the parts left inside your blocks with the bearings removed) and they are then very difficult to rotate. I donít know why they sometimes send them out like this.

I had a friend turn up 2 spacers on his lathe and all was well.

Either ask the supplier where the spacers are
Or get someone to make up some spacer tubes

If you check my YouTube channel (routercnc) episode 5 shows me building up a ballscrew and mount. Note the brass buffers are nice to have but could still work without. Here you will see the spacers you need.

In terms of bearings then you have the budget ones. As Clive says you can optionally upgrade to AC bearings but either way you need the spacers.

Fancy
16-01-2019, 02:46 PM
I talked with the seller and it was a heated phone call and he said i didn't know what i am talking about and went to say that it's because of my inexperience that i am not able to get them to work right but at the end told me to ship the ballscrews and the blocks and get my money back so i am going do that and never am i gonna deal with him again. Thanks for the help guys much appreciated @Clive @routercnc.

Clive S
16-01-2019, 05:24 PM
I talked with the seller and it was a heated phone call and he said i didn't know what i am talking about and went to say that it's because of my inexperience that i am not able to get them to work right but at the end told me to ship the ballscrews and the blocks and get my money back so i am going do that and never am i gonna deal with him again. Thanks for the help guys much appreciated @Clive @routercnc.

You only need to have the spacer tubes made. Changing the bearings to AC type will be better. If you send them all back you may not get the postage back.