Replace bearings in BK12 & BF12 fittings

I have cheap ass bearings in my ballscrew mounts can I pop them out and replace them with better ones off the shelf?

I want to replace the bearings in the BF12 fittings first. One bearing squeaks when I'm cutting at 10m/min, so I thought replace all 4 bearings with proper SKF deep groove.

Then buy the correct angular bearings to replace the ones inside the BK12 from China and replace when they arrive.

1. Are SKF 6008 deep groove bearings what I want for the BF fitting?
2. Should I buy the rubber sealed or the Z version?
3. 6008 is the size right? So as long as I buy a 6008 it will fit?
4. Which size angular bearings do I need for the BK12 and how many?
5. What does clearance mean on SKF bearings, have a choice C3 or Normal.

Thanks

Seems I need a 26mm OD, 10mm ID will 8mm thickness be ok?

Replace them with normal.
When it comes to fitting angular contact to fit in BK blocks, finding the size at a decent price you'll be lucky.

Get the machine running and make your own bearing blocks for the angular type.
I'm running 2x 32x12x10mm AC bearings on a 1605DFU ballscrew drive end in both budget and Dunlop brands and I'm happy. Paid like £6-£10 each.

The floating end has a 30x10x9mm which cost me £5 for a single row and £12 for a double row so I can see which is better.

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Originally Posted by Desertboy

5. What does clearance mean on SKF bearings, have a choice C3 or Normal.
Thanks

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The C rating is the amount of radial play available when cold - C1 is the least, C5 the most, C3 is in the middle obviously and seems pretty common. The reason for the larger play is to allow for expansion when the bearing heats up I think??

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Originally Posted by dazp1976

Replace them with normal.
When it comes to fitting angular contact to fit in BK blocks, finding the size at a decent price you'll be lucky.
.

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You're not wrong there. When I wanted a couple of high quality AC bearings last year I found that the cheapest way of getting them was to buy a high spec. (FBT) BK12 from Fred @ BST and take the bearings out of it! OK I had an order running already so no big postage, but given that the saving was over £10.

These are the AC contact bearings I plan on using when I replace the rubish deep grove bearings in my Chinese BK12's for my Z axis.

http://www.wychbearings.co.uk/7001-2RS-MAX-Enduro.html

I haven't got them yet, so I can't comment on quality.

For my X and Y axis I made my own bearing block as dazp1976 suggested using larger bearings and my mini-lathe. Although if I knew wynchbearings sold 7001 at a reasonable price way back when I made them I would have just bought cheap BK12s and replaced the bearings.

I found I had to shim my AC bearing to remove play. I used a mixture of 0.1mm shim washers and some thinner ones I cut out of some brass shim shock. They all feel rock solid now.

https://www.ebay.co.uk/itm/A2-Stainl...DHNWICz7gz71SQ

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Originally Posted by diycnc

These are the AC contact bearings I plan on using when I replace the rubish deep grove bearings in my Chinese BK12's for my Z axis.

http://www.wychbearings.co.uk/7001-2RS-MAX-Enduro.html

I haven't got them yet, so I can't comment on quality.

For my X and Y axis I made my own bearing block as dazp1976 suggested using larger bearings and my mini-lathe. Although if I knew wynchbearings sold 7001 at a reasonable price way back when I made them I would have just bought cheap BK12s and replaced the bearings.

I found I had to shim my AC bearing to remove play. I used a mixture of 0.1mm shim washers and some thinner ones I cut out of some brass shim shock. They all feel rock solid now.

https://www.ebay.co.uk/itm/A2-Stainl...DHNWICz7gz71SQ

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I've been using these a while.
https://www.ebay.co.uk/itm/7201-B-2r...oAAOSwBRVaWdEz
In terms of needing shimming it depends on how you make your blocks to house them. Mine need none, just have to watch how tight I do the end nut.
I've now ordered these to go on the floating end: https://www.ebay.co.uk/itm/3200-B-2R...72.m2749.l2649
I've found that if I put a bearing up tight on this end it eliminates about 0.02mm of my 0.035mm of backlash. A little bit of flex in the screw by the looks of it.

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Originally Posted by Voicecoil

The C rating is the amount of radial play available when cold - C1 is the least, C5 the most, C3 is in the middle obviously and seems pretty common. The reason for the larger play is to allow for expansion when the bearing heats up I think??

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I was just looking at bearings on the CNC4YOU website and was wondering what the difference is/was between the C ratings that they sell. Saying that though, and with reference to you saying that C5 was the max, their cheaper option seems to be a C7 and it seems the average difference between their C3 & C7 varieties is about a tenner. So... Is it normally worth paying the extra?

Cheers

Quote:

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Originally Posted by joe.ninety

I was just looking at bearings on the CNC4YOU website and was wondering what the difference is/was between the C ratings that they sell. Saying that though, and with reference to you saying that C5 was the max, their cheaper option seems to be a C7 and it seems the average difference between their C3 & C7 varieties is about a tenner. So... Is it normally worth paying the extra?

Cheers

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The SKF ones I got from ebay were C3, £7.50 for 3 of them, need a hydraulic press to fit them.

Only replaced the squeaky one so far but it no longer squeaks so a bonus.

This is only for the floating end.