Supported rail or other?

**lateAtNight** · 11-11-2008

If you had the choice, for an aluminium router, would use supported rail, or precision linear rails. You know the ones with the carriages, rather than the bearing blocks?

Pros and cons of each?

Cheers,
Dave.

**Lee Roberts** · 11-11-2008

The supported rails are better then the unsupported mate, however if its your first machine look at what you want it to do, if you get 20mm rail over a shorter distance then you would get a way with it. Getting one up and running first, then look at the cost side of it and build to your budget.

Once your more in the know, maybe spend a little more and build an even better machine.

Have a read of this post: http://www.mycncuk.com/forums/showthread.php?t=256

**lateAtNight** · 11-11-2008

What about these?

http://www.slidesandballscrews.com/2...50783c1223df24

**lateAtNight** · 11-11-2008

Its just after Kieth saying in effect saying my first design was crap, I went back to the drawing board. It got slightly better, but now for a third time (and hopefully final time) I re-designed, to... (see pic). Which uses linear rails.

I'd rather have linear rails because the attach easily to aluminium profile, where as supported rail, i would need to do lots of drilling etc. So what I was basically asking was, can I get away with using the rail, or is round supported better?

**Lee Roberts** · 11-11-2008

Have a look at this machine: www.cncdudez.com

Let me know when you want to buy the ali frame i can get it quite cheap!

**lateAtNight** · 11-11-2008

Cheaper than KJN?

http://www.aluminium-profile.co.uk/a...m_Profile.html

**Lee Roberts** · 11-11-2008

No sorry they are about the same.

**Gary** · 11-11-2008

What are you looking at machining? Looking at your design either supported round rail or the profiled rail would do.
I think the 20mm profiled rail is a bit of an overkill for hte size of you machine? and 15mm would be fine.
With the round rail you can also use the SHF mountings for supporting the rail and this will connect direct to the aluminium profiles with t slots.

Gary

Originally Posted by lateAtNight

Its just after Kieth saying in effect saying my first design was crap, I went back to the drawing board. It got slightly better, but now for a third time (and hopefully final time) I re-designed, to... (see pic). Which uses linear rails.

I'd rather have linear rails because the attach easily to aluminium profile, where as supported rail, i would need to do lots of drilling etc. So what I was basically asking was, can I get away with using the rail, or is round supported better?

**lateAtNight** · 12-11-2008

Lee; thanks for the link. There is some interesting stuff on there.

Gary... Yes the 20mm was over kill, I was just messing around. Although I find it quite funny that you knew it was 20 just from the pic :D. 15 it is...

Do you mind me asking if Zaps linear rails are the same as Marchant Dice? There seems to be a fair price difference, but you seem to have bigger carriages, so I am assuming thats where the price difference comes from?

Do you think I could get away with using 2 carriages on the Y axis?

Looking to machine aluminium... Small (ish) parts, but quite deep probably... ie i'm not just making signs or engraving.

**Gary** · 12-11-2008

The reason i said that the 20mm profiled rail is most likely an overkill, was based on the design of the machine and what he is machining.
This is just an estimation because no real data is available, but the the basic loading of the BRH15 is 850kgf (dynamic) and the BHF20 is 1450kgf.

How much load will machining small pieces of ali impose on the bearing?

I cant imagine it is anyware near what the bearings is capable of?

Originally Posted by Kip

How is it overkill to use 20mm rail....As far as using a single carriage...forget the notion......Check the spec sheets for details/differences between manufacturers parts.

Bearing in mind that cutting forces have to go somewhere and the bearing surface on linear bearings is very small compared to oilite bushes and dovetails......