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Lathe Leveling and Headstock Alignment

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ptrotter

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#1
Now that I have gotten a little experience with my new PM-1340GT I decided to recheck the leveling and see what my headstock alignment looks like. First, out of curiosity, I checked the runout of the spindle. Using a Brown and Sharpe .00005 test indicator I found the TIR to be .0001. Quite impressive. Checking the runout on my 3-jaw chuck showed a TIR of .0022. Not great but then it is not a high end chuck.

To check headstock alignment I chucked a 1.5" piece of 6061 stock and turned a band at both ends. I measured a taper of .0044 over 9 inches . Not what I wanted to see so I spent quite awhile adjusting the lathe leveling feet to remove any twist in the bed. After removing the bed twist as best I could, I rechecked the alignment and got a taper of .001 over 9 inches. I'm not sure it is worth trying to get any better at this point. I am curious as to what others are seeing when checking their headstock alignment.

Next project is a tailstock DRO.
 

ddickey

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#2
I'd say for a nice new lathe like that .0005" over that distance would be more acceptable.i have.0005" in 7" on an eighteen year old lathe.
On a side note I can not level my lathe using the leveling feet. I must shim the bed directly where it is bolted to the stand.
 

Technical Ted

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#3
I use a precision level to get my lathes level, but then tweak things in after taking test cuts like you are by just adjusting the lathe's feet (I tapped screw adjustments in the four location on my SB lathes). This way you can get it very close with very little taper (if any).

So, a level to get it close, tweak to get it dead on.

Ted
 

ptrotter

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#4
Thanks for the replies. After thinking about it some more, I realized which foot needed to be tweaked to get the movement I wanted in the bed and I was able to get the taper down to .0002 over 9 inches. I still haven't gotten using a micrometer on a round surface down perfect so my measurements may be a little off but it looks much better.

I am using a length of 1.5" 6061 for the test cuts and i can see a significant difference in the surface finish at the ends of the rod. I'm not sure how much impact this is having on my test cut. I am also noticing a little variation in the x-axis DRO reading from one end of the cut to the other. Would it make sense to lock the cross slide and compound slide when making the cut to ensure that they can't move at all?

I love the VFD. I can vary the speed and watch the surface finish change.

I'm slowly learning.
 

Richard King 2

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#5
A good way to learn how to mic something is to buy a 1 2 3 block and measure it over and over again. BUT close your eyes when you mic it. when you think and you got it you should be able to slide the mic. Look at it, write down what you got and then open it up a turn and close your eyes and do it again. and again, etc. Also when you take your test cuts, be sure to have a sharp tool bit or insert and take some dry cuts or cut it, then shut down the spindle and DONT touch cross feed screw. slowly crank the saddle back and take a cut free, or dry, no feed in. This eliminates the possibility of push away.

Be sure to lock the leveling screw lock nuts after your happy. I hope you have leveling plates under the leveling screws. :)
 

Alan H

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#6
Paul, here are a couple of threads here on leveling and aligning a PM1340GT that may be of interest to you.

Leveling
Alignment
 

starr256

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#7
I have my PM1030 on a steel framed bench with a 2" maple top. I worked really hard to get the bench level, using lasers and screw levelers. Had it dead on. The bed was also level. Then I turned a test bar. Had 0.004" variation over 6". Argh! More adjusting the level of the bench. No change. Spent the night mulling. Next morning I loosened the hold down bolts, put a couple to sheetmetal shims between the head and the bench. Boom. Got repeated cuts with vatiation of less than 0.0005" (limit of my mics). Learning, always learning.
 

NortonDommi

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#8
A micrometer has a little screw on the end with a clutch in it to keep measuring pressure the same for each measurement. Two clicks is more accurate than feel. Shear tools are are good for final cut as you are only taking off a thou or so.
 
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