Trueing a CNC Spindle

Instructions on how to "tram" or "sweep" a CNC spindle that has gotten out of plumb. January 25, 2013

I have a SCM Pratix 48. It seems my spindle is a little out of plum in the Y direction. When I run the spoil board cutter back and forth on the x axis, it is leaving small ridges. I was wondering if anyone has done this adjustment. I called a tech who said they could look at it shortly after X-mas, but now it is middle of Feb.

Forum Responses
(CNC Forum)
From contributor M:
You basically need to sweep or tram the spindle. A quick search on Google should give you plenty of results. We flycut the way it is and then suck down a good clean piece of MDF. If you have a dial indicator, you can make your own fairly easy.

From contributor Z:
This looks like a real nice tool and the price is great too: Pro-Tram from

From contributor J:
When I tram out a spindle, I always use a machine grade granite surface. I run the spindle front to back and left to right on this plate with a dial gauge. Once I level out the granite surface without rotating the spindle, I then center the spindle on the plate and rotate the gauge around. This will let me know in the X and Y direction how to adjust the spindle. Some techs will perform this on the spoil board. I don't, as it isn't accurate enough.

This is one of the best ways to perform this function. It just takes time to level out a spindle. If the spindle is out left to right, you just loosen the bolts and adjust the spindle. If the spindle is out from front to back, you will have to loosen the spindle and adjust by adding or removing shims accordingly. You don't want to rush this - plan to spend 4-8 hrs performing this.

From contributor A:
I agree with contributor J. If you cannot acquire a granite plate, a rectified, straight platen will also work. It must still be trammed first. For the money, I recommend for tramming spindles for routers - more than accurate enough.

From the original questioner:
Thanks for all the info. I have never done this, so I don't know which bolts I have to loosen and adjust! Or where I would shim. That is the part I am trying to figure out, as the manual or the parts section doesn't show much.

From contributor J:
The bolts you would loosen would be the ones that are directly holding the spindle to the z-axis plate. There are usually 6-8 bolts total. They should be running up and down the side of the spindle. You would loosen these bolts and adjust the spindle left and right. If the spindle is out from front to back, then you place shims behind the spindle where these bolts are. This way you hold the shims tightly between the spindle and the back plate. If you look at the top of the spindle and where it is mounted to the z-axis back plate, you will see the bolts holding the spindle in position.