Interested. Please send details.
1 Like
I’ll PM you the details.
Alex
More tramming experience - I followed advice from Alex McClure (thanks!) and moved my Z-Slider to middle hole. This allows tramming gauge to swivel underneath the Z-Slider. I zeroed the X-axis tram by loosening and v-e-r-y carefully retightening the two router mount screws while observing the twin gauges - tightening the top screw tends to shift the X axis one way, tightening the bottom screw reverses that. For the Y-axis tram, I ended up shimming the Z-slider at the top with a .020" feeler gauge as the shim; this corrected the “nod” of the router to within .0015" (it was .005"), which I’m calling done.
3 Likes
Just sent you an email. 
Alex
I had to remake the spoil board because of Z-Slider hole move. Resurfaced. Tested on .75" pone with surfacing bit. Not happy. So I pulled out the glass to recheck tramming. That’s when I decided to chuck the glass and order granite surfacing slab from Lee Valley. In for a penny, in for a pound, as they say. Stay tuned.
1 Like
I am in the midst of calibrating my new set-up, and ordered the same granite. I noticed a discrepancy between the advertised accuracy (.0001") and that on the certification card that accompanied the granite (.0002"). I have emailed them and they said they would let the appropriate departments know. They even opened a box of their own and confirmed what I found was also in their box.
Not a deal breaker for the price. They said I could return it, but I do not plan to. It should match the accuracy and repeatability of what I am currently finding.
1 Like
I wonder how flat a piece of granite countertop is compared to the surfacing slab.
The difference in flatness could possibly be inferred in that surfacing slabs are presented with flatness tolerances while the countertop slabs are not.
But now I want a kitchen countertop rated to ±0.0001 so I can achieve perfection in cooking… because obviously it’s the weak specs of the countertop to blame and not my overwhelming lack of cooking skills. 
4 Likes
How do you guys know your surface is perfectly flat when you’re doing these tramming calibrations?
It’s typically determined by chucking a dial indicator capable of measuring flatness deviations to 0.001. You’d observe the needle moving on the indicator as the gantry is manually moved along the board (but hopefully not if the board is actually flat).
The low-fi setup employs something like two drill bits embedded in a piece of wood, one bit chucked to the spindle / one zero’d to the board, that’s manually rotated around the board along with use of feeler gauges to discern discrepancies in flatness.
1 Like
Yes but how do you know your deviations are coming directly from your router and not from the boards you are using to calibrate? Especially because you wouldn’t have been able to surface a board correctly.
Good point and that also alludes to the answer: if the spindle is not perpendicular to the work surface, it leaves signs of this in how it leaves the surface after surfacing, typically ridges left behind due to one side of the bit always being higher than the other.
If it’s obvious enough to see and feel, you know it’s time to break out the tramming solution to figure out by just how much the spindle’s out of perpendicularity so you can correct it.
1 Like
Ignore that this is being done on a vertical mill. The same principles will apply. This demonstrates yet another way you can determine spindle perpendicularity, assuming you’ve already determined that your spoilboard is parallel to your X / Y plane via surfacing.
I wouldn’t rely on this youtuber’s illumination test but employ feeler gauges to determine what the exact discrepancies are so I could dial things in with higher tolerances but you’ll get the idea.
That’s one of the arguments for a certified reference surface. A certified granite slab isn’t terribly expensive and can provide you with a flat surface to make your measurements off of with your dial indicator.
1 Like
So something like this? HHIP 4401-0011 Granite Surface Plate, Grade B, Ledge 0, 12" x 9" x 3": Amazon.com: Industrial & Scientific
Check the questions for that. “National Bureau of Standayds” certified, even!
I mean, if you can’t trust the standards determined by the National Bureau of Standayds, what can you trust!
That’s the one I used.
You can get by with a smaller one 6x6 is probably enough but I liked having the larger size for my tramming setup - dial indicator on a 6" horizontal mount.
Timely topic.
I am currently referencing my 9"X12"X2" Lee Valley granite block to my XY plane before tramming.
I have my 2 micron dial test indicator in an ISO20 toolholder.
Running my spindle along left to right along X and the 12" length it reads:
-.02mm > 0mm > +.02mm > +.015mm > 0mm at the start,1/4, 1/2, 3/4, and end intervals respectively.
I will continue this at different Y locations, then do the same in the perpendicular directions.
The certificate states accurate to 0.0002" (~0.005mm). There was no +/- but I will assume it is 2X the value so a variation of ~ 0.01mm. In my first run I am recording 4X that. We’ll see what the other readings show.
My dial test indicators are the best and worst instruments I have purchased - I need to stop chasing unrealistic and perhaps unnecessary zeros 
2 Likes
I’m not judging. I have 3ds Max precision set to 5 decimal places and have grown accustomed to working at that level of precision, though I possess absolutely no means by which to achieve anywhere near that level of precision. A lot of it lost in the transition from 3d space to reality… and I’m not okay with that either. 
I think the Starrett block for $350 is only half the variation the Lee Valley one advertises. Might let you chase another fraction of a fractional fraction
1 Like