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Voicecoil
10-10-2018, 09:30 PM
I've just been getting a quote from Fred at BST for some custom length ballscrews, in his last email he mentioned the option of superior quality end bearings, which apparently have P5 Angular contact ball bearings in the BF (floating) end. They're about $24 per screw more expensive, just wondering if anyone had any experience of them please and whether they're worth the extra dosh??.

Cube3
11-10-2018, 08:08 PM
Hi,
I took the better option and they are well worth the money. Wouldn't buy anything else and Fred is very helpful
Simon

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driftspin
11-10-2018, 09:29 PM
I've just been getting a quote from Fred at BST for some custom length ballscrews, in his last email he mentioned the option of superior quality end bearings, which apparently have P5 Angular contact ball bearings in the BF (floating) end. They're about $24 per screw more expensive, just wondering if anyone had any experience of them please and whether they're worth the extra dosh??.Yes i have them too.

Make sure Fred sends you bearing sealed at the blocks or self sealing bearings.

Please check my buildlog there is pictures of what went wrong in my order.

I agree Fred is the best... he solved the seal issue for me once he understood the problem.

I have no experience with lesser quality bearings but yes i like the superiors.

Grtz Bert.

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magicniner
11-10-2018, 10:53 PM
Just visit a decent Industrial Bearing Supplier and tell them what you need, generally you get better products at a fraction of the online prices!

Boyan Silyavski
15-10-2018, 12:43 PM
I used that setup on both sides of my screws and was very happy from it. I don't see the point of using floating end on a properly made CNC, given the small price to pay.

Voicecoil
16-10-2018, 12:01 AM
So am I right in thinking that this kind of setup is essentially working like having fixed bearings at both ends? - there's an obvious advantage in reducing "whipping" at high speeds that way. Would some preload help even further, or does "just-and-so tight" sort most of it?

Cube3
16-10-2018, 09:52 AM
https://www.linearmotiontips.com/choose-end-fixity-conditions-screw-applications/

Be careful of thermal expansion on Fixed/Fixed long leadscrews.

Regards
Simon

Voicecoil
16-10-2018, 09:59 AM
Thanks for the link. It sounds like Fred is offering the "double floating" variety of bearing then.

Another thing that struck me today was that (if you have space for them) having 2 "floating bearings" spaced a bit apart ought to resist whipping, whilst not giving any problems due to thermal expansion. The thermal expansion thing I guess will only be a major problem on machines made from dissimilar metals anyway e.g. aluminium frame with steel ballscrews. I was quite suprised how much it could be when I did the sums for my design, about 0.5mm for a 1700mm long machine with a 20 degree C change.