View Full Version : BK15-C7 ball-screw supports

06-08-2012, 04:36 PM
Has anyone made their own ball-screw supports?
My machine uses CNCRP bearing blocks for my 2 start screws and the standard BK15-C7 supports will not work without some major modifications to the frame to align the steppers to the ball-screws.
I could try a belt/pully setup which might be a better choice...

Thanks for the help.

06-08-2012, 11:14 PM
SteveSpo made some.

Here is his build thread:


06-09-2012, 07:05 AM
It might be easier to get flange type bearing blocks (FK, FF) and a custom mount for them...

06-10-2012, 11:52 AM
Making your own bearing blocks is not complicated, but I wouldn't say it was fun. A milling machine would make short work of this, but I did everything with my router and cutting aluminum is a bit messy.

They're really very simple. On the motor end, I used (2) matched 7200B 30x10mm angular contact bearings. They need to be used as a pair and you adjust the preload with shims and some trial and error (or maybe a tension scale if you're being precise).

So, it's 1/2" aluminum plate with pockets that are just a hair shy of the exact depth of the bearing. The bearings are a slip fit and then you shim the inner races between the two bearings to adjust the load.

As you tighten the locknut on the ballscrew, the races get pulled together and you want them to meet up with the correct resistance. The two plates are attached with some cap screws and then the whole thing just bolts to my 8020. It's pretty easy to do and hard to describe until you have them in hand.

On the other end, it's just a standard R6ZZ deep groove ball bearing and it's pocketed into a single piece of aluminum. With the AC bearings on the motor end, most people just use a single bearing on the opposite. The bearings are all from VXB (vxb.com).

Depending on how your ballscrews are machined, you'll need to spec out different bearings. My shafts had several steps. It was turned down to 10mm, then threaded for a locknut, then turned down to accept the 1/4" motor shaft coupler. On the other end it was turned down to .375" to take the other bearing.

I'll post my drawings later, but they're pretty specific to my machine.

06-10-2012, 01:08 PM
Great explanation Steve!
As I said before my machine uses the bearing blocks and thrust bearings from CNCRP. What I want to do is make a drop-in replacement for the CNCRP blocks. I’m sure there are others using the CNCRP frame designs and parts that might benefit from this if they want to go with ball-screws instead of ACME threaded rod. I’m wondering if I can use the CNCRP blocks as a starting point, replace the bearing that is in there and make a second housing for the second AC bearing. Getting the existing bearing out of the CNCRP block might be a challenge and finding a bearing that fits will be another.
I understand routing Ali is messy as I have done quite a few pieces on my router but in the end it should be worth the hassle.
I still need to determine which ball-screw to purchase for my machine given the electronics used and frame size.