Linear Way Saddle
 

I'm working on a mid size CNC mill with linear rails. I've got a lot of it
figured out including squaring it up as its built. The goal is a mid size
bed mill with very good acceleration to optimize use of a high speed
spindle. Hence linear ways (amoung other things) for its construction.
Sometimes though the simplest things seem to hang me up.

Optimally for support the bearing blocks both on the top and bottom of the
saddle would be at the outside corners of the saddle, and the saddle would
be a similar size (in X&Y) to a dovetail saddle relative to the machine. If
this is the case the bearings blocks over lap each other on opposite sides
of the saddle making it impractical at best to bolt on the bearings. If I
make either dimension longer so they do not overlap then I lose a lot of
travel. If I make either dimension between the blocks shorter for the same
purpose I lose more stability and support than I care to. The table is
modestly heavy and I do need to minimize sag from table weight.

The only solution I have come up with is to make the saddle out of two
pieces that are keyed for alignment and then bolted together after the
bearings are mounted to their respective halves.

I am hoping one of you guys will have a simpler more elegant solution.

Linear Way Saddle
 

On Thu, 16 Feb 2017 11:23:44 -0700, "Bob La Londe"
wrote:

I'm working on a mid size CNC mill with linear rails. I've got a lot of it
figured out including squaring it up as its built. The goal is a mid size
bed mill with very good acceleration to optimize use of a high speed
spindle. Hence linear ways (amoung other things) for its construction.
Sometimes though the simplest things seem to hang me up.

Optimally for support the bearing blocks both on the top and bottom of the
saddle would be at the outside corners of the saddle, and the saddle would
be a similar size (in X&Y) to a dovetail saddle relative to the machine. If
this is the case the bearings blocks over lap each other on opposite sides
of the saddle making it impractical at best to bolt on the bearings. If I
make either dimension longer so they do not overlap then I lose a lot of
travel. If I make either dimension between the blocks shorter for the same
purpose I lose more stability and support than I care to. The table is
modestly heavy and I do need to minimize sag from table weight.

The only solution I have come up with is to make the saddle out of two
pieces that are keyed for alignment and then bolted together after the
bearings are mounted to their respective halves.

I am hoping one of you guys will have a simpler more elegant solution.



Are you aware that the both the cars and rails are available with
either tapped or clearance mounting holes? See THK or IKO.

--
Ned Simmons

Linear Way Saddle
 

"Bob La Londe" wrote in message
...
I'm working on a mid size CNC mill with linear rails. I've got a
lot of it figured out including squaring it up as its built. The
goal is a mid size bed mill with very good acceleration to optimize
use of a high speed spindle. Hence linear ways (amoung other
things) for its construction. Sometimes though the simplest things
seem to hang me up.

Optimally for support the bearing blocks both on the top and bottom
of the saddle would be at the outside corners of the saddle, and the
saddle would be a similar size (in X&Y) to a dovetail saddle
relative to the machine. If this is the case the bearings blocks
over lap each other on opposite sides of the saddle making it
impractical at best to bolt on the bearings. If I make either
dimension longer so they do not overlap then I lose a lot of travel.
If I make either dimension between the blocks shorter for the same
purpose I lose more stability and support than I care to. The table
is modestly heavy and I do need to minimize sag from table weight.

The only solution I have come up with is to make the saddle out of
two pieces that are keyed for alignment and then bolted together
after the bearings are mounted to their respective halves.

I am hoping one of you guys will have a simpler more elegant
solution.

Thomson rod bearings have mounting flanges:
http://www.thomsonlinear.com/website...xtra_rigid.php

-jsw

Linear Way Saddle
 

On Thursday, February 16, 2017 at 10:23:53 AM UTC-8, Bob La Londe wrote:
I'm working on a mid size CNC mill with linear rails.

Optimally for support ... the bearings blocks over lap each other on opposite sides
of the saddle making it impractical at best to bolt on the bearings.

If the bearings have a square base, drill out two (diagonal) of the four threaded mount holes;
bolts from below into the NE and SW holes, and from above into the NW and SE holes.