Couple questions linear shafting

[justCNCit]

I was looking at Enco for some of their steel precision shafting. My CNC wood router uses skating radial bearings at 90 degree angle (45 to horizontal) to guide itself on the cold rold shaft thats on there right now.

However I have been exploring the option of switching to precision rod because the cold rold steel used at this time is warping and is only tied down at the ends.

Looking at Enco's supply, I can't seem to tell whether or not the shafting I'm looking at has screw holes in it to actually lock it into position on the machine frame. How do you tell.

Also after its picked up, how would you level out these shafts onto the same plane over 6' x 4' bed. There must be SOME trick to tuning it in without $$$ and lots of it.

[MrKal]

Hi there just,

I'm a bit new to CNC too but since the other members didnt reply i'll
offer at least one suggestion for leveling the table.

The idea is to build the whole machine totally, with adjustments for both
rails at both ends of each rail to adjust the height. This will allow you
to adjust the height of all the ends of the rails (or shafts) later.

After this is built the head will be in place too (with or without any cutter).
This means you can swing the head around the whole table and make
measurments at various places between the head and the table (vertical).
You have to pick a reference point on the head to measure from or just
mount a short piece of shaft in the chuck (or even a cutter). You could
then make your measurements between the bottom of the shaft (or cutter)
to the top of the table at various places.
The key places to measure would be in the four corners. If one corner is
low that means that end of the shaft has to be raised. If high, lower it.
If low and you run out of adjustment range to bring it high, then lower
the other three corners.
Eventually you will reach a point where all the corners measure the same
distance from the top of the table. You can then check other points to
see if you have sag, which you cant adjust unless your bearing type
allows supports midway under the shafts. If you have not selected your
bearings yet then perhaps you can select the open type so that you
may add more supports later if needed.
There are equations you can use to estimate the amount the shafts
will bend when you apply the load. This will help you select the right
shaft diameter depending on the number of supports possible.

[justCNCit]

Can't believe I never thought of that. Excellent thought, thanks.

[blackbeard52]

Could you provide some pictures of your machine bed to allow us to give more help. There are many ways to do what you are concerned about. typically non supported rails over that distance is going to flex and there are several ways to secure them after the fact..

Bob

[justCNCit]