Aligning the threads in the shaft

[kiinstructor]

Hey guys, I have a question about aligning the threads in the shaft. I use a chuck to hold the shaft on the front side of the lathe and a chuck with an indicator in the back side of the lathe to hold the shaft prior to milling the threads. I mill my 3/8 10 threads with a router mill that makes nice smooth threads. Im happy with that part but what Im finding is, after I mill the threads I put in a pin to check to see if they are perfectly staight and they are but after I take out the shaft and go to sand it. I put on a sanding mandrel and chuck it in my sanding lathe and put the tip end in a live center and find I have a slight wobble in the shaft in the middle. Makes me think I cut the threads at an angle. If I take the live center off the tip end of the cue and just hold it the shaft seem to be straight. The mandrel pin seems to run straight so whats the problem. Makes me wonder if the shaft being held straight when Im machining the threads or am I looking at this wrong. Any help will be appreciated.

THanks
Makr

 

[BLACKHEARTCUES]

You may have the tailstock too tight. If so, you are bowing the shaft. Loosen the tailstock & see if that takes care of it...JER

 

[rhncue]

You may have the tailstock too tight. If so, you are bowing the shaft. Loosen the tailstock & see if that takes care of it...JER

I agree and this can happen in other areas also. When turning the shaft this is critical if you want them to be cut true and straight. It takes very little pressure on the shafts ends to make an affect. In my shaft machine I have an adjustable tension spring that can be set differently for heavier or lighter cuts.

Dick