View Full Version : How to plumb Z axis? Laser? Dial Indicator? Other?

Kevin Fitzgerald
12-23-2002, 11:13 AM
What is an easy way to fine-tune the plumb of the Z axis? I was thinking of either an arm with a dial indicator, or a laser attached perpendicular to a 1/2" steel stud chucked in the router.

12-23-2002, 11:49 AM
Kevin, It's not really high tech, but I've had a lot of luck over the last 5 years using a simple $3 circular "bubble level" mounted on top of the router itself. Maybe with the newer router brackets it's a little different, but I've been able to tweak my hose clamps with shims to get a pretty straight up/down cut..Bill P.

12-23-2002, 02:10 PM
Kevin, a simple trammel with a 1/4" bent rod soldered into a piece of precision 1/2" round bar, scribing a radius of around 6" is enough. You can use a feeler gauge under the tip for real accuracy, but we generally just check that it scribes with equal pressure all the way around.


Don't be surprised if you get different results depending on where your car is sitting in the gantry. There may be flex or twist in your gantry.

Of course, you must unplug the router before you mount the trammel . . . .

12-23-2002, 05:19 PM
I just did this about a month ago for my initial setup...and found that the torpedo level that I used prior to flattening the table was WAY off!

The Colombo has a nice flat/square body that I clamped a 4' (high quality) level to. After using the 4-footer, it is dead on. I tried using the laser level, but it really isn't practical for this type of thing...mainly because it is difficult to get it to where it is actually usable. According to the laser level instructions...It's only accurate from 2+ feet and on. Not a good idea for close up things.

As far as fine tuning goes...A dial indicator would probably be the way to go if you want it absolutely perfect. Remember that there will be some fluctuations in the ganty position no matter what you use. (Sag/dips in the Y carriage etc)

I would imagine that you could use the dial indicator on a stand set to the bottom edge of the router housing. Move the indicator "around the clock" and see if it is high or low. Then adjust it accordingly. This is of course assuming that the router housing is true all the way around and square to the rotating spindle.


12-23-2002, 08:31 PM
You can rig up Gerald's method even easier and "lower tech": start with a scrap of wood something like a 1x2. A foot long is fine but length is not critical. Drill a hole in one end just big enough to slide a pencil into. Drill a 1/2" hole in the other end.
Now stick a pencil into the first hole and the 1/2" drill bit into the other hole. (A little hot-melt glue works wonders to hold everything together.) The pencil point should be pointing down, and the shank of the drill bit should be sticking up.
Chuck the shank of the drill bit in the router (unplugged, of course) and spin the whole contraption by hand as you lower the z-axis until the pencil just touches the table.
If your axis is true, the pencil point will just touch all the way around.
You don't need the gizmo itself to be particularly accurate, since as you swing it around through 360 degrees it will always be off the same amount in any direction. The longer the wood, the more sensitive the test.
Sometimes simple and cheap is best!
David B.

12-23-2002, 11:33 PM
All the above posts, including mine, do not answer the title of this thread. All the posts are about plumbing the router and not the z-axis. They are two different things.

For setting the z-axis perpendicular to the table, we use a large steel square resting on the table and touching the z-axis slide.

12-24-2002, 08:17 AM
I first 'surface' an area of the table. I then 'square' the spindle of the tool to the table. I proceed from there to 'square the axis'.

To do this I have modified my "Y-Z" carriage junction as shown. I punch a hole with the tool (a 1/4" bit shown here) and insert something that fits, amazing a 1/4" bit fits here (that means my router bearings are not too shot). I raise the Z as shown in the picture and adjust as necessary.

If adjustment is needed, one must go back and square the router axis to the table. This can be done by placing shims between the router base and the Z axis.

Support (Admin)
12-24-2002, 11:09 AM