Tailstock Alignment

ddickey

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I checked my Tailstock alignment the other day. Dialed it in for zero movement on the indicator for the first half of the lathe bed. Then it started to move out of alignment, went to two thou then settled back to one thou at the back of the bed.
Why would this be?
It's best to have it aligned the first half of the bed where the cutting will take place, correct?
 
I believe it is a 2000 model. Makes sense I guess. As the height of the tailstock moves upward would cause a movement in the indicator.
 
In which direction was the TS centre deflecting?
Slight vertical movement does not have as much impact as horizontal movement (i.e. front to back).

PS As Peter writes below, we have to expect measurement errors in some set-ups. The most reliable test for TS alignment is a turning test that is measured with a micrometer.
 
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When you say 'dialed it in' can you elaborate on your test setup?
- as in confirming tailstock deviation of in/out vs. up/down from headstock spindle axis?
- where was the DTI located? (I can visualize the indicator mounted on a rotating headstock part & confirming tailstock axis alignment in close range.. but how would you have accomplished this with the tailstock positioned way out at the end of the lathe?)
- assume you are using a DTI vs dial gage? Some people have reported variations of the dial gage plungers when pointing up vs. down (maybe spring loading or gravity acting variations?)

I found chasing-my-tail variations when checking my tailstock setup. Amazing how 1-2 thou can creep into mix that had nothing to do with axis alignment. Examples: Chucking a dowel pin in tailstock chuck is asking for trouble because chuck's runout/grip will likely vary even with a precision model. I think inserting an accurately ground MT collet with dowel or an MT arbor with extended stub & indicating around that is less error prone. And even with that probably best to leave in same position throughout tests for consistency & remember to lock the travel spindle the same. Check that tailstock underside is 100% clean of slightest particle debris. Check for edge casting burrs or anything that might cause variation & use consistent tailstock clamping pressure.

I've been tempted to get one of these precision ground MT/straight test bars, but I'm not exactly sure of proper usage / implementation. Does one set in tailstock & now the (long extension) magnifies tailstock deviation by indicating around the end from headstock mounted DTI? I thought another use might be to insert in headstock (with MT5/MT3 adapter) as a means of validating head alignment to lathe beds & carriage travel or setting up taper turning angle zero datum, but I'm not sure that would give me better results than what I'm doing now.

12-3-2016 0001.jpg
 
Are you just checking for the heck of it? Everything you check on a used lathe will give you questions. I would just use the lathe. If you notice something while using it that prevents you from making a part. Then, I would check and fix. If you use your machines long enough. You will learn there idiosyncrasies and can then still make decent parts…Good Luck, Dave
 
When you say 'dialed it in' can you elaborate on your test setup?
- as in confirming tailstock deviation of in/out vs. up/down from headstock spindle axis?
- where was the DTI located? (I can visualize the indicator mounted on a rotating headstock part & confirming tailstock axis alignment in close range.. but how would you have accomplished this with the tailstock positioned way out at the end of the lathe?)
- assume you are using a DTI vs dial gage? Some people have reported variations of the dial gage plungers when pointing up vs. down (maybe spring loading or gravity acting variations?)

I found chasing-my-tail variations when checking my tailstock setup. Amazing how 1-2 thou can creep into mix that had nothing to do with axis alignment. Examples: Chucking a dowel pin in tailstock chuck is asking for trouble because chuck's runout/grip will likely vary even with a precision model. I think inserting an accurately ground MT collet with dowel or an MT arbor with extended stub & indicating around that is less error prone. And even with that probably best to leave in same position throughout tests for consistency & remember to lock the travel spindle the same. Check that tailstock underside is 100% clean of slightest particle debris. Check for edge casting burrs or anything that might cause variation & use consistent tailstock clamping pressure.

I've been tempted to get one of these precision ground MT/straight test bars, but I'm not exactly sure of proper usage / implementation. Does one set in tailstock & now the (long extension) magnifies tailstock deviation by indicating around the end from headstock mounted DTI? I thought another use might be to insert in headstock (with MT5/MT3 adapter) as a means of validating head alignment to lathe beds & carriage travel or setting up taper turning angle zero datum, but I'm not sure that would give me better results than what I'm doing now.
I used a two morse taper stub arbors. Plunger type indicator mounted on my tool post on middle of arbor. Started at the headstock with the tailstock forward with the headstock. Everything locked down. Took measurements down the bed and no deviation until just past halfway. The has been leveled but is due for another check.
 
When I "dial in" my tailstock it amounts to inserting centers in both headstock and tailstock and viewing them through a magnifier to see if they line up. I usually do that when I am checking the height. I adjust side to side when turning a piece between centers. It works for me.
 
If I'm looking for "perfection", I set the tailstock where it will be used for the work piece and turn 1" aluminum rod without moving the cross slide or compound...then mic the ends.
 
I do that also after I check alignment with the stub arbors.
 
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