How to attach metric ball rails to aluminum extrusion?

[dinkyguitar]

Hi,

I'm planning on building a CNC machine using aluminum extrusion, (1530) but I noticed that the mounting hole for a ball rail is metric, 6mm (I believe) but on the aluminum extrusions they use a 5/16" bolt which is a larger slot in the aluminum.

Are there special screws for this?

Basically I want an FLA-100 machine with ball rails instead of the linear carriage bearings....Or is this a waste of time and money.


dinkyguitar

[ger21]

I'd just drill them out.
But there are two rows of holes, usually 30mm apart. Are the slots 30mm apart?

[HorridHenry]

So drill the ball rail mount holes to 5/16 if its possible?

[louieatienza]

You should be able to get t-nuts with a 6mm threaded bore....

[RicknBeachcrest]

I think drilling them out would be very problematic. This is not just steel, it is hardened steel. The kind they need to cut with an abrasive cutting wheel.



This is one of the current problems I am in the process of solving now.

This is my plan, YMMV.

I placed a bar of 1/8 aluminum with oversize holes drilled out to match the rail. Then I got Socket Head Cap screws that would attach the rail to the extrusion, with the aluminum bar in between. Now the problem is a what to screw these cap screws to. You can make your own nut system by welding a nut to a modified fender washer. You can use T-nuts, which I have tried. Or (my latest) is to have 8020 surplus pre-drill and tap the required holes in a bar of steel. Page 230 of their catalog.
80/20® Inc. - The Industrial Erector Set®

You may want to check out my build thread as I am building an 8020 machine.

http://www.cnczone.com/forums/cnc_wo...ter_build.html

[jharvey407]

Hi,

I'm planning on building a CNC machine using aluminum extrusion, (1530) but I noticed that the mounting hole for a ball rail is metric, 6mm (I believe) but on the aluminum extrusions they use a 5/16" bolt which is a larger slot in the aluminum.

Are there special screws for this?

Basically I want an FLA-100 machine with ball rails instead of the linear carriage bearings....Or is this a waste of time and money.


dinkyguitar

If you're using metric rails, why not use the metric extrusions.

When I was designing my machine I decided to the use the IVT rails, which come in metric sizes, so I used the metric 8020 extrusions and everything matched up perfectly.

[louieatienza]

I'd just drill them out.
But there are two rows of holes, usually 30mm apart. Are the slots 30mm apart?

I believe they are if using base 30 extrusion...

[RicknBeachcrest]

Here is a source for t-nuts.

T-Nuts - Bosch Rexroth Corp.

[dinkyguitar]

Thanks everyone....

RicknBeachcrest, 2 questions...

1. Those ball rails you are using, can they be mounted on top of the extrusions? I always see them used (mounted) on the sides of extrusions...I thought using them on a top rail (for the gantry) would distribute the weight better than using them on the side...

2. The rails you are using from automation-overstock.com, do they have CAD drawings of them? I'm designing my CNC machine using Linear Motion SHS20 rails and I have 3d drawings so I know precisely how far apart parts are.

BTW Good build thread

dinkyguitar

[ger21]

I think drilling them out would be very problematic.

I thought he was talking about round shafts and I meant drilling the aluminum supports.

I have the same rails that Rick has. They have a .pdf with all the dimensions. I use those to make my own CAD models.

[microcarve]

Drilling Hiwin rails is easy. I've done several.

It's only the edges where the track grooves are that's
hard....and it is hard.

It's actually nice steel to drill due to the quality of it.

Still, I'd bolt it to something else before I'd bolt it to any extrusion.

Extrusions aren't as flat as they look. Rails are also a little flexible.
Smaller sized rails...20mm for example....would conform to the
irregularities in the extrusion and confound the heck out of someone
for days....and days.....when the blocks/trucks bind in places.

Found out the hard way.

Test any rail by using a center punch. If it makes a dimple...it can be
drilled....(in most cases)


John

[Walky]

If you're using supported round rails (SBR and such), just drill them a little bigger (remove the rail before doing it!).