View Full Version : Ball nut brackets, how big do they have to be ?

10-03-2014, 01:32 PM
It's fair to say I come from the 'brick shithouse school of engineering' and so when I look at this ball nut bracket I start to wonder.

Ball Nut Mount/Bracket Nut Mount For 1605 1604 1610 16mm Ball Screw CNC Router | eBay (http://www.ebay.co.uk/itm/Ball-Nut-Mount-Bracket-Nut-Mount-For-1605-1604-1610-16mm-Ball-Screw-CNC-Router-/191082066288)

I'm going to use it for the Z axis front plate and weighing the assembly it comes to just over 14kg, that's with the spindle motor attached. As you can see the bracket is fastened to the front plate with 4 x 5mm studs, now my question is, does that strike you as being strong enough ? it's only shear forces involved I think and I can't cut a recess in the front plate that it could sit in.

I could tap it to 6mm but then there is less 'meat' left on the bracket itself around the holes.

Clive S
10-03-2014, 01:56 PM
Eddy I am sure 5mm bolts will be plenty strong enough. I will be interested to hear about the quality of those brackets they are not worth making at that price inc. del. Good find:congratulatory:

10-03-2014, 02:08 PM
I got these ones Aliexpress.com : Buy CNC BALL NUT HOUSING, MOUNTING BRACKET FOR 2005 BALL SCREWS from Reliable nut wheel suppliers on lishui city hengli Automation Technology co., ltd. (http://www.aliexpress.com/store/product/CNC-BALL-NUT-HOUSING-MOUNTING-BRACKET-FOR-2005-BALL-SCREWS/407448_946453714.html) and they too have M5 tappings, I'm sure we're not the only ones to use these and I can't remember hearing of any problems. Found this after a quick Google Mechanical engineering other topics - Shear Limit of M5 Bolt (http://www.eng-tips.com/viewthread.cfm?qid=60863)

10-03-2014, 02:09 PM
Clive, I'm pleased to hear you think so.

Well it arrived today, it's a thing of beauty, made from aluminium it's sides are as smooth as silk, no machine marks anywhere, nicely tapped holes, sprayed or anodised black.
Took 15 days to arrive from China.

10-03-2014, 02:13 PM
Neil, going by those calc's it should be okay to say the least.

Clive S
10-03-2014, 02:26 PM
Well over a ton or even a tonne then, you could put your car on it.:friendly_wink: ..Clive

10-03-2014, 02:50 PM
Thanks for that chaps, now I can get it fitted.