# torque value for LMS 3990 mill column bolts



## ARC-170 (Mar 30, 2019)

I'm trying to tram up my mill for the first time. I noticed it matters a great deal how much the mill column bolts are torqued down, since I get different readings after adding what are supposedly the correct thickness shims, only to have the dial indicator tell me it's still off. Going by feel clearly isn't working. I can get the column to move 0.003" or so just by rotating the wrench 1/8 of a turn.

Are there particular torque values for the bolts or should I just be consistent? What is a good value to use?


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## darkzero (Mar 30, 2019)

Look up the recommended torque spec for the size bolt you need, choose a logical rating & torque them all the same. You don't have to use the actual recommened value & keep in mind that torque ratings differ for bolt types & applications. Consistency is most important here.


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## benmychree (Mar 30, 2019)

Where are you putting them shims; if not directly under the bolts, you may be warping the casting, causing the inconsistent readings.


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## hman (Mar 31, 2019)

Might there be a high spot somewhere between the bolts?  If so, changing how hard you reef down on various bolts could be causing the column to "rock" one way or the other on the high spot. 

In any case, +1 on benmychree's and Will's comments.


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## 9t8z28 (Jun 18, 2019)

I was looking for the same information a while ago. I found the appropriate torque specs for the factory hardware and wrote it down  at home. I’m at work now and I will try and get it for you tonight.   It’s only inch pounds. Do you have an inch pound torque wrench?


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## royesses (Jun 18, 2019)

Standard toque by bolt diameter and class:


*Bolt Diameter
 (mm)*​*Recommended Torque
 (Nm)*​​​*Class 8.8**Class 10.9**5*79*6*1216*8*3040*10*5575*12*100135*14*160215*16*245335*20*480650



8mm bolt torque
30Nm = 22.1268644783181 ft/lb

40Nm = 29.5024859710908 ft/lb



1.3558179483314 Nm  = 1 ft/lb

1 Nm = 0.73756  foot pounds

Roy


Roy


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## markba633csi (Jun 18, 2019)

Something seems off there:   If 1Nm = 1.35581 ft/lb.  then
30Nm should be equal to 30 x 1.35581 = 40.67


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## royesses (Jun 18, 2019)

markba633csi said:


> Something seems off there:   If 1Nm = 1.35581 ft/lb.  then
> 30Nm should be equal to 30 x 1.35581 = 40.67



30Nm x.735756 = 22.1268
40Nm x .735756 = 29.5024

I wrote the conversion wrong. I'm claiming old age as the culprit. Thanxs for catching that.

Roy


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## markba633csi (Jun 18, 2019)

No problem,  one of my few clear headed moments, just happened to notice that


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## ARC-170 (Jun 20, 2019)

Thanks for the info. I looked up standard torque values for bolts and I think I used 30  lb-ft. I've got the mill up and running. Seems to cut square!


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