I moved my PM1340GT to its permanent position and leveled it. The PM1340GT is meant to be leveled and then the headstock aligned using its adjustable mount.
This post is about the head and tailstock alignment methods I used. I recognize that this is not the only way to do it nor have I invented anything new. I am just trying to share the process I used for others who might find it helpful. Key to the process I settled on are a good four jaw chuck, a 1” precision ground steel test bar, and a 2”diameter aluminum bar for test cuts.
The sequence I used:
- Aligned the tailstock using the “quick method”.
- Aligned the head using my four jaw chuck, a 1” round precision ground bar, and the Rollie’s Dad Method. (Note: if you aren’t familiar with the RDM, google it and you will find lots of info)
- Realigned the tailstock using the quick method.
- Turned a 2” diameter aluminum test bar with two collars using 4 jaw chuck and between centers.
- I did test cuts with the 2” two collar bar to confirm head alignment (w/o tailstock)
- I made a test bar out of 1” precision ground bar and confirmed tailstock alignment with it.
I aligned the tailstock to the head using the “quick method” as described in the PM manual (page 30). Works extremely well if you have two pristine centers and a single edge razor blade for a test plane. The blade is held between centers and the tailstock alignment adjusted until the test plane is perpendicular to the centerline of the spindle.
I used an 18” long 1” diameter precision ground bar that I bought from McMaster mounted and trued/indicated in my 4 jaw chuck. I then used the Rollie’s Dad Method (RDM) to confirm and correct a misalignment of about .0035” at 12” from the 4 jaw chuck. I loosened the 4 head mounting socket head screws and then snugged them back down but not full torque. I used the two adjustment screws on the side of the headstock to tune the bar to zero runout using a 0.0005” indicator. To say the head alignment is sensitive to the adjustment screws and the mounting screws tightening would be an understatement. I discovered if I pivoted the head on a fully tightened right front head mounting screw, I could then use a tightening sequence that maintained the runout. I tightened the right front mounting screw fully, then front left and then two rear bringing them all down partially and evenly a little at a time. When finished, the RDM was showing the zero runout that I was after.
With the head now aligned using the RDM, I realigned the tailstock to the head using the quick method. I turned a 12” long 2” diameter two collar aluminum test bar between centers using the 4 jaw chuck (test bar trued in chuck). Here's the test bar with two collars ready to go:
With live center support removed, I did test cuts on the two collars (one with a HSS tool and one with a CCMT insert). Using a micrometer to the tenths, this confirmed the headstock was aligned. To my surprise the RDM for the initial alignment was quite accurate and no adjustment was needed. Here are the test cuts:
I chucked the 18” long steel test bar in the four jaw. I center drilled the ends and confirmed concentricity of the center drilling both ends. By the way, my test bar has a surface hardness of RC60 and the center of the bar ain't soft.
Then using the center drilled test bar between fixed centers, I confirmed the tailstock alignment. This confirmed the “quick method” for tailstock alignment works well.
In summary:
- I am glad to have my lathe in its final location and leveled on it six footed stand. I will use my leveling method in the future as needed. (thread on leveling)
- The Rollie's Dad Method (RDM) of alignment with my 4 jaw and precision ground test bar will be my go-to method for rechecking head alignment from time to time. A good precision ground test bar is critical and I have preserved mine for next time. With the test bar trued up in the 4 jaw chuck, the RDM is easy to use. I did preserve my two collar test piece for future use if needed but I bet it gathers dust.
- I trust the “quick method” for tailstock alignment. I have also put my centers in a safe place to preserve their "as new" condition for use next time.
Sorry for the long post but I hope this helps someone figure out how they want to work through this on their machine.