Nod tuning Questions

My mill came in late December, so it is a newer shipment. I used the shim calculator for the z axis, it recommended three shims on the top. After surfacing the base plate, I could feel the nod in the baseplate. I used 2-4-6 blocks for a for a larger sample, and actually had to remove the 3 shims top recommended by the online calculator and add all the bottom shims. The interesting part is. On 6 inches tested against a 2-4-6 block and a very accurate machinist square at 6 inches. The indicator starts at zero and ends at zero of the 6 inches travel. However, in the first 3 inches the indicator goes negative .002. it did this regardless of where the shims were placed. I tested the Z travel with the first recommended shims and it went negative .002 and then +.006. Then after removing the top shims and putting in all of the lower shims it still goes negative .002 in the first 3 inches but then returns back to zero. Any ideas?

Contact customer service. You are likely experiencing the casting issue that some people have found.

Unless of course, you’re ok with it. It’s pretty involved to replace the casting.

Most likely your casting is slightly bowed. I have a similar issue but I guess it is within the tolerance of this machine.

Yep, mine did the exact same thing as well. Here’s a video I had taken of mine sweeping .003+" over 6". I used a .0001" DTI to really highlight the bow. I ultimately had projects that needed done, so moved on and haven’t had any accuracy issues or problems meeting spec. If you do contact Langmuir, I would also be curious if this is something that should ultimately be addressed.

6" sweep - Nod tuning process


I would also be very interested in seeing a Tramming video.


rotate the block 90 degrees and test again. I have a couple blocks with dips in the middle.

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figured i would use this thread. getting tilt done now and specs say no shims, however i have exactly .020 out using a 2x4x6 block. added two shims on bottom and now at .017. going the right way but going to run out of shims lol. @langmuir-daniel is that to much shim? I figured i would cut open a soda can for some thicker shims lol

In general, you shouldn’t use more than 3 shims for any shimming application, and you shouldn’t need to. Consolidate them by using thicker shims.

Using a large stack of shims means you will have sliding and a buildup of springiness in the stack. You want a rigid connection. 4-5 is borderline, more than that bad practice.

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