41B & 42B Head Clamp Block Installation Torques

Feb. 11, 1972
Mar. 9, 1972 Update

Applies to: All 41B & 42B machine after 1963:

Be ABSOLUTELY sure that the head clamp block screws are properly torqued on each machine installation and/or on routine service calls.

Double-check the blocks on machines shipped with the head removed. On any machine shipped with the head removed, it is possible you will find the screws 'finger-tight'. The blocks will have been removed during shipping to allow the clamp gib to be removed.

Anytime the head clamp mounting bolts are disturbed, it is necessary to:

1. Completely remove the bolts.
    
2. Clean the bolt threads and the threads in the head to remove all traces of the previous application of thread locking compound.
    
3.  Apply Loctite NUT LOCK to the bolt threads.
    
4. Properly torque the bolts into the head.

This is very important. The screws are more than adequate to hold the blocks, but WILL fail if allowed to operate loose. Broken bolts can damage the Feedback system components that are mounted nearby and may well require removing the head from the column to allow the broken pieces to be removed.

The proper bolt torques is as follows:

Models with (3) 3/8-16 bolts per clamp assembly:
50-55 Lb-Ft for Hex Head Cap Screws
     65-70 Lb-Ft for Socket Head Cap Screws

Models with (3) 1/2-13 bolts per clamp assembly:
125-130 Lb-Ft for Hex Head Cap Screws
     165-170 Lb-Ft for Socket Head Cap Screws

It is also an ABSOLUTE necessity that the Hex-Head bolts be 'Grade 8', or better, for this application and that the Socket Head Cap Screws be rated "265,000 PSI at 1000 Degrees F".