# Lathe head alignment



## Larry$ (Jul 5, 2021)

Yesterday I finally did it. I have a PM1440HD and it has always cut a slight taper. I ordered a bar of 2" 12L14 to do the setup as outlined in the manual. Sounded straight forward. I chucked up the 8" long bar in the 6" 3 jaw. Sharpened a 5/8" HSS tool that has considerable easing on the nose. Took a couple of passes to cleanup the bar. Was getting chatter at the far end. A lot of overhang! Changed to a heavy 8" 3 jaw still a slight amount of chatter at the far end. Changed tools to a 90 degree Vee, my chamfering tool. No chatter. 

Measured diameter near the chuck then at the end, .004" different, Yikes worse than I had expected. Repeated everything to verify, same answer. Get my biggest Allen wrench and it won't fit into the pockets where the bolts are. Grind several times and get a fit. Needed a considerable cheater to loosen the bolts slightly under the chuck. The bolts on the change gear side require the main gear, banjo and a guard to be removed to get at the bolts. Lots of cheater again. I put a mag base with dial test indicator on the end of the turned bar so I could tell how much it moved. Adjusted the push pull bolts in the change gear space. Tighten the mounting bolts. Put the banjo & gears back in and take another test cut. Measure with the 2" micrometer, off by .002. Repeat process, getting greasier every time. Do it again, went too far! Do it again, a bit too far the other way, .001 off.  Do it again barely moving any thing. Off by less than .0005. Each time the bar got a bit smaller (.005" cuts) in diameter. At the .0005 in 6" point,  I called it quits. Tighten everything, Banjo & gears back on, check gear clearances, put guard back on, sit in front of fan, it's 95 degrees and I'm exhausted.

Is this close enough?


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## Just for fun (Jul 5, 2021)

I can't help you with your question.  But sounds like you worked hard at it.  Good job!


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## markba633csi (Jul 5, 2021)

Sounds fine to me, any time you need another grease fix you can always do it again 
-Mark


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## MrWhoopee (Jul 5, 2021)

You got lucky! I would have chased that thing all over the place and been relieved when I got it back where it started.

Now how about the 2 collar test?


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## benmychree (Jul 5, 2021)

Above comment suggests that you should relieve your test bar in the middle (A small amount), leaving a full size "collar" at each end, perhaps 3/8" wide to do your test cuts on, this speeds up the process and removes most potential tool wear from the cuts.


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## Larry$ (Jul 5, 2021)

MrWhoopee said:


> Now how about the 2 collar test?


It's on my to do list. Getting the tail stock (almost) dead on seems a lot easier than all the chasing I did on the head stock. 
When I ordered the 2" bar stock for the head alignment I got a selection of smaller bar stock. So I now have some to make the two collar bar. 
I got 96#s of 12L14, 4' long steel bar from Midwest, two cartons. Freight was $50 which was cheaper than I had thought it might be. 
I need to get some cast iron to make a gib for my cold saw. Have been looking for scrap but no luck so far. I really don't like machining cast iron.


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## RJSakowski (Jul 5, 2021)

I would check a facing cut.  My attempt to correct a turning taper by adjusting the headstock messed up the cross slide alignment so I was cutting a cone.  

You can check by facing a large diameter piece and checking with a straight edge. Another way is by mounting a button on your face plate and zeroing a test indicator on the button when in a front position.  Then rotate the button to the rear and without disturbing the carriage or compound, move the cross slide to intersect the button.  If your cross slide is perpendicular to the spindle axis, the indicator should read zero.   The carriage should be locked for this test.


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## Larry$ (Jul 5, 2021)

RJSakowski said:


> My attempt to correct a turning taper by adjusting the headstock messed up the cross slide alignment so I was cutting a cone.


Thanks, I'll do as you suggested.  If it turns out the cross slide is not perpendicular to the bed axis is there a fix? The bed is what everything must be adjusted to.


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## RJSakowski (Jul 5, 2021)

Larry$ said:


> Thanks, I'll do as you suggested.  If it turns out the cross slide is not perpendicular to the bed axis is there a fix? The bed is what everything must be adjusted to.



Here is a description of my procedure.








						On the Level: Further Adventures with the G0602
					

When I built the stand for my G0602 lathe, I made leveling adjusters for the four legs.  They were simple in design; a 1/2-13 bolt  and jam nut threaded into a plate at the bottom of each leg.  However, in trying to precision level the lathe, I ran into some issues.   When adjusting the height...




					www.hobby-machinist.com


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## ddickey (Jul 5, 2021)

Only close enough if the T.S end is larger than the HS end. T.S end can never be smaller than the H.S end.
Did you take spring passes after your cuts?


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## Larry$ (Jul 5, 2021)

RJSakowski said:


> Here is a description of my procedure.


Went back and read it. 
My lathe weighs about 2700#s, sits on the 6 factory supplied leveling bolts & pads, No issues with wondering about. 
I haven't checked for concavity with a face plate, good idea. 
I was getting so hot & tired that I was trying to get it done. I had recently re-checked front to back twist with my very good level and adjusted it slightly. To get uniform pressure on all bolts I've used crow's foot sockets on my torque wrench. Not so sure that's any better than just the "feel." Didn't check end to end level as I don't really care about that. Whatever it still is from the original setup is what it is. 



ddickey said:


> Did you take spring passes after your cuts?


I did on the first few iterations but had found no measurable changes so I didn't on the last half dozen tries. 
I need to go back and check see which end was larger. Why does it matter? 
Even getting slightly different tensions on the push/pull adjusting bolts affected the rotation of the head. Or maybe it was how snug I had the mounting bolts while trying to make adjustments? Having to take the change gears and banjo off/on for each try was a PIA. 

At any rate I need to go back over everything when its not so damn hot and I'm not exhausted. Then move on to the tailstock end adjustments.  Thanks for the input guys.


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## ddickey (Jul 5, 2021)

I believe it has to do with tool pressure/deflection during a cut.
See Pg. 53 figure 8. Then reference 8b on the next page. https://springfieldarsenal.files.wordpress.com/2018/10/schessinger_testing_machine_tools.pdf
Wes shows it in his video here ~ 10:30


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## Larry$ (Jul 6, 2021)

I attempted to reduce the side force when cutting by using sharp, almost pointed HSS, not carbide inserts.  I had a 2 " diameter 12L14 bar sticking out about 7" from a heavy 8" chuck. I seriously doubt that there was measurable deflection. The tool was sticking out of the holder less than .5" The compound was back and locked, the cross slide was locked. 640rpm .005 DOC, .0008 feed per rev. Cutting oil lubed. I was producing nice but small C or 6s chips not Xmas tree decorations. Measurable deflection? I'll give it another go when it isn't so hot.


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## Larry$ (Jul 6, 2021)

This morning I did all my measuring, rechecked the bed for twist. I concluded my results were likely as good as it is going to get, with me at the controls.


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## Larry$ (Jul 7, 2021)

MrWhoopee said:


> Now how about the 2 collar test?


Just finished that. The tailstock was off a bit. Now corrected as good as I can. 
That completes the lathe improvement project. The problem now is .... I can't blame the lathe for some of my less than ideal results.


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