The Importance of Pre-Alignment to Shaft Alignment

These Simple Pre-Alignment Steps Save Time

Most of the problem calls from technicians made while they're conducting a shaft alignment are the result of a failure to perform any pre-alignment activities. The following pre-alignment steps are important contributors to a successful shaft alignment that is completed with just one or two moves.

Step 1. Check for Soft Foot

Once the machine has been properly locked out, before loosening any foot bolts, do a quick soft foot check of the feet of both the stationary and the moveable components. Using a 0.005" shim or feeler gauge, try to insert the shim under the component feet. Measure for soft foot at three corners of each foot, if three corners are accessible. If the shim will go halfway to the bolt, under any corner, make a quick note of which foot, or feet, are "soft". A more thorough soft foot check will be done next.

Step 2. Rough Correction of Soft Foot

Loosen all foot bolts on the moveable machine. Using a pry bay, apply slight lifting force under the foot, and measure for soft foot with a shim, or feeler gauge. Add shim as needed to correct for soft foot. Then continue on to the other feet on the moveable machine, until a 0.002-0.003" shim or feeler gauge cannot be inserted under the foot. Be mindful of an angular soft foot. If a moveable machine foot has an angular soft foot, you may have to cut a partial shim or shims to correct for angular soft foot.

Step 3. Rough Alignment

This process is often overlooked by mechanics, but it can save time in achieving precision alignment, and help to reduce gross errors in the alignment process. Using a straightedge, check the tops of the coupling flanges for parallelism. If a gap exists while checking for parallelism, measure the gap with a shim, or feeler gauge. Insert the measured amount of shim under each of the moveable machine to bring the components into rough vertical alignment. Repeat the procedure on the sides of the coupling flanges to correct for rough horizontal alignment. Be sure to tighten the feet of the moveable machine back down before beginning alignment. After completing the rough alignment process, you are now ready to begin alignment.