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I Decided to Align the Tailstock Today...

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MrWhoopee

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I had not checked the tailstock on my '63 SB Heavy 10L since I got it in November. It had been in storage for 10 years prior and served as "the good lathe" in an old line manual shop before that. I set-up the Last Word on the jointed round mount that came with it and put that in a 3/8 collet in the spindle. Brought the tailstock up, zeroed the dial inside the taper and spun the spindle. It registered .003 tir vertical, .000 horizontal. Put away the indicator and called it a day. Should buy some lottery tickets.
 

Bob Korves

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If the vertical runout showed the quill lower than the headstock, that is fairly easily repaired by shimming between the two halves of the tailstock.
 

MrWhoopee

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If the vertical runout showed the quill lower than the headstock, that is fairly easily repaired by shimming between the two halves of the tailstock.
Don't think I didn't consider it, for about 2 seconds. Given how little that amount of drop would affect turning with a center, I wasn't about to risk making it worse just to chase .0015.
 

machPete99

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Some of that runout might be from the deflection in the indicator when flipped. It is often more than you might expect.
You could try using a test bar between centers to check, with the indicator on the carriage, check across the top and front side.
 

T Bredehoft

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Some of that runout might be from the deflection in the indicator when flipped.
Every indicator I've checked, (a fair number) will not hold zero on rotation. Gravity is too effective.
Center drill both ends of a piece of Drill Rod (longer the better) and put it between a freshly turned center In the chuck and a center in the tails stock. Run the indicator along the top of the Drill Rod to see vertical alignment.
I once mounded an indicator on the end of a shaft in a lathe, feeler against a pin on the mounting surface and rotated the shaft. The Last Word I was using registered .002 movement. Nothing moved but the guts of the indicator.
 

MrWhoopee

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Hadn't considered that there might be some movement as the indicator rotates, but I won't be attempting to get this thing any closer. I know there is a tendency to push for "absolute" precision, but this is a 55 year old South Bend, not a Hardinge HLV. I'm stunned and ecstatic that it's this close. It will make absolutely no difference for drilling and tapping, and the effect on turning will probably amount to less than .0002. More than good enough for the girls I date.
 

Janderso

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My south bend 13 tailstock took a .010 brass shim on each side. I am very happy with the results now.
Great lathe for the money.
 

MrWhoopee

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Since I started this thread, I decided I should actually check the alignment using the 2 collar method. Here's my setup:

WP_20180420_13_15_43_Pro[1].jpg

The center to center distance on the collars is about 14.25.
I got .0003 difference, the collar at the chuck being smaller.

Think I'll let it alone.
 

Janderso

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3/10’s ah yeah, you lucky dog.
I need to determine my tail stock alignment using your set up, looking for a taper over 14”. Twisted ways, worn ways, Head stock alignment etc.
Everything I have done so far on my 77 year old lathe has been accurate enough.
When I gain a higher skill level, I may need to tighten up my tolerances.
The cross feed and compound screws and nuts are new.
Thank you for posting.
 

westerner

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Think I'll let it alone.
Whew! I am glad I ain't the only one. I realize this entire hobby/occupation/obsession is about accuracy and precision. I get that, really. However, my time in the construction trades has taught me that if you are ever gonna get the job DONE, ya gotta KNOW what you can get AWAY WITH! I have worked with a few people across several occupations that could never get something FINISHED, because they insisted on achieving a level of accuracy that was not relevant to the job.:faint: I, for one, have stated here and elsewhere, that I DO NOT have a contract with NASA, or Boeing. I strive for accuracy, and for improvement in accuracy, but the primary focus is on getting the job done, to the satisfaction of the customer. I take the lessons I learn from the job, and apply it to the next one, rather than obsessing over goals that do not apply. Sorry, rant over. Thanks for letting me vent!
 

MrWhoopee

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When I had my shop, we had a Clausing Colchester 15 and 17, Mori-Seiki 17, Howa Sangyo 17, Hardinge HLV and a couple of other more forgettable lathes. I'd be happy with .0003 over 14 in. on any of them. I'm stunned that my SB Heavy 10 is that close. In a job shop environment, you can't afford the machinist who will continue to chase a dimension after it's in tolerance. Perfection is not possible, close enough is.
 

thenrie

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Whew! I am glad I ain't the only one. I realize this entire hobby/occupation/obsession is about accuracy and precision. I get that, really. However, my time in the construction trades has taught me that if you are ever gonna get the job DONE, ya gotta KNOW what you can get AWAY WITH! I have worked with a few people across several occupations that could never get something FINISHED, because they insisted on achieving a level of accuracy that was not relevant to the job.:faint: I, for one, have stated here and elsewhere, that I DO NOT have a contract with NASA, or Boeing. I strive for accuracy, and for improvement in accuracy, but the primary focus is on getting the job done, to the satisfaction of the customer. I take the lessons I learn from the job, and apply it to the next one, rather than obsessing over goals that do not apply. Sorry, rant over. Thanks for letting me vent!
Hehe. I understand what you're saying, but 3 TEN-THOUSANDTHS over 14-1/4" inches is even good enough for NASA and Boeing!
 

Bob Korves

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Since I started this thread, I decided I should actually check the alignment using the 2 collar method. Here's my setup:

View attachment 265621

The center to center distance on the collars is about 14.25.
I got .0003 difference, the collar at the chuck being smaller.

Think I'll let it alone.
I suspect that the factory specs for that test would be somewhere around zero to .0005" toward the tool post and the same for tailstock center height, zero to .0005" high. You are golden...
 

pacifica

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Hehe. I understand what you're saying, but 3 TEN-THOUSANDTHS over 14-1/4" inches is even good enough for NASA and Boeing!
A friend of mine who works for NASA said actual tolerances (beyond the blueprint) are frequently in the 2 thousandths range,.
 
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