Question On Aligning The Lathe Spindle And Bed Twist

Update on where I am at this point. I will list the steps I took before making a cut on the faceplate.


1. Evened out the loading on each foot and then leveled the lathe side to side and front to back trying to keep the load on each foot equal.


2. Loosened the 6 mount bolts that attach the lathe to the stand. Ran the lathe for 1 min to allow it to settle on the stand and then tightened all 6 bolts.


3. Rechecked the level, didn't seem to change. The lathe running with only the chuck, no test bar, had a noticeable shake/shimmy (350 rpm). I tweaked the loading on the front tailstock foot (increased) which got most of the shimmy out. This did affect the level a bit front to back but the feet require equal loading to get rid of the shimmy so I left it where it was at.


4. Removed the chuck, the lathe now ran very smooth. No shake/shimmy.


5. Mounted the faceplate and setup for a skim cut. I locked both the carriage and compound and made a skim cut. This cleaned up the complete faceplate surface.
setup.JPG

6. With a dial indicator on the carriage I measured the faceplate runout. I had to measure one side at a time, resetting the indicator due to lack of enough travel. I redid this measurement several times and got the same results each time.
measure1.JPG
measure2.JPG

I measured .0015" on the half of the faceplate closest to me starting at the outside edge and moving toward the hole in the center of the faceplate. When I did the same measurement on the other half of the faceplate I saw a total of .003". This was over a 3" distance on each side. The surface of the faceplate is now slightly concave which is the opposite of what I expected based on the results of the test bar. The test bar was smaller in diameter at the end closer to the headstock which had me thinking the spindle centerline was pointing slightly toward the rear of the lathe but that would have resulted in a convex surface so not sure what's going on at this point.


Questions:


1. Why would I get different runout measurements on the 2 half's of the faceplate when I sweep across the face? It didn't make sense to me, that's why I re-did it several times.


2. Should I tweak the alignment of the headstock? It seems to be out compared to the cross slide but how much? Using the 2 indicator method described by joshua should I set the one indicator to .0015" and tweak until both read the same value?


3. Why would the test bar results indicate the headstock angled toward the rear of the lathe while the faceplate results indicate it's angled toward the front of the machine. Or am I just looking at this all wrong.
 
Yes for #2, absolutely adjust the headstock. This method does work, there is a lot of great information here, but I prefer the test bar method. Getting the headstock true on these machines is part of setup. Larger or older lathes many times had the headstock fit to the ways and it was not able to be moved. These lathes have an adjustable headstock on them, it is done with the bolts we talked about yesterday above the motor.

The thing is that if you use the face plate method, that is a good way, but the best way is with a test bar. Because 99% of the work you will probably be doing is going to be turning longer pieces, and thats where you want the best accuracy to be. And I find it to be a lot easier to do it with the test bar method. You don't want to take too many cuts on the face plate, or you won't have a face plate left.

The face plate method is a good way to do it too, but I prefer to have it dead on with the left to right travel. And while the cross slide travel on this machine is going to be very, very close to the travel of the bed ways, it is probably not going to be .0000, so I prefer to have the left to right travel to be the one that is dead on. I've done many shafts and parts that had to be perfect, but almost never when facing.

I explained that in an email I sent to you this afternoon, maybe check your junk folder, I have sent you 4-5 emails since we talked yesterday afternoon. This is copied from the one email, if you need any help, please feel free to call, I left my cell phone number in there too. I am still here for a couple hours this evening.


Step #1, level the bed, by putting a level on the cross slide, and running up and down the ways. As long as it is close, you are good here.

Step #2, to the test cut and see where you are. Adjust the headstock as necessary. I prefer a piece with a smaller diameter if you have it, 2-1/2" diameter I would think would be a little much for the jaws of that chuck to hold. I would go more with a 1-1/2" Piece that can fit a bit in to the bore of the chuck, at maybe 6" Long out of the jaws and use that as a reference. Take your test cut with that, and use that as a reference to adjust the headstock in. Get it as close as you possibly can with those adjustment screws we talked about, it may take some time to get the feel of how to do it. I've done them in 10 minutes before, and sometimes it has taken a full day to get it dead on.

Step 3, once the headstock is aligned, you can align the tailstock at this point if you would want to, but really, it may be offset to turn tapers, etc. so you might want to wait until your first job comes up that you will use the tailstock for.
Remember, every alignment like this on the lathe is just an adjustment, but do them in the order above. Do not tweak the level on this machine to get taper out, do that with the headstock adjustments.
 
Also, that is an excellent explanation of the headstock nod not really having much effect on the diameter. It does the slightest bit, but I find that a lot when dealing with a tailstock that is a few thousandths high or low on various machines. I try to explain that to people, but now I have a great reference to point to!
 
Monday I'll pick up a length of 1.5" material and try PM's method as described above.
 
Since the predominate advice is to adjust the adjustable headstock for side-to-side squareness, couldn't the headstock be trammed into place?

It appears the front of the cross slide is a ground surface.

Using one of these doo-dads:

202-0009-2_1.jpg
 
question one should be:
How is it possible that you get any reading in the first part of the measurement going in on the faceplate?
The indicator is mounted on the compound and should follow the exact same path the cuttingtool followed.
The measurement on the part going out of the faceplate is logical.
Then indicator will follow the path of the cutter going in, even past the centre where the faceplate actually is coming out.

on edit:
after thinking about it the only way to explain the measurements, which are consistent, is that the faceplate gave way under the pressure of the cutter.
More towards the outer rimm , lesser towards the centre.
As a problem also exists while turning in a chuck i suspect the bearings of the spindle need adjusting.
 
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Monday I'll pick up a length of 1.5" material and try PM's method as described above.

If you need to borrow a MT5 test bar, I can loan you mine. I bought this from Brian Miller, Miller Machine and Fabrications, when I aligned the headstock on my 1236 lathe.
 
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question one should be:
How is it possible that you get any reading in the first part of the measurement going in on the faceplate?
The indicator is mounted on the compound and should follow the exact same path the cuttingtool followed.
The measurement on the part going out of the faceplate is logical.
Then indicator will follow the path of the cutter going in, even past the centre where the faceplate actually is coming out.

on edit:
after thinking about it the only way to explain the measurements, which are consistent, is that the faceplate gave way under the pressure of the cutter.
More towards the outer rimm , lesser towards the centre.
As a problem also exists while turning in a chuck i suspect the bearings of the spindle need adjusting.

The indicator will (should) register 0 run out when sweeping between the front of the lathe and the center line.
The indicator will reveal a convex or concave profile when sweeping between the centerline and the back of the lathe.
If you have trouble visualizing it, think of one of those little clockmakers lathes that have a rotating head stock. You can rotate the head stock and face a part to put a point on it.

I agree it does sound like he had some push off during the cut. This is almost for sure caused my incorrect technique, not loose bearings. These lathes are all broken in at the factory, they do not ship with loose bearings. On the other hand, turning cast iron is not an intuitive process. People tend to try and make light skim cuts that are shallower than the tool radius and get all sorts of problems hitting dimensions. What is important is that the he got different measurements on the front half than the back half, this is indicates a rotated head stock.
Matt says he should adjust it after reading the thread, and he is the guru.
 
These lathes are all broken in at the factory, they do not ship with loose bearings.
Really? No room for mistakes? My bad, i thought Taiwan was part of China not Switzerland.

Different measurements on the front half than the back half do not indicate a rotated headstock.
ALL lathes have different measurements.
The measurement on the front half should read zero and the one on the back half should read double the deviation from perpendicular.
In fact the reading he got is perfect as it is, but for the fact that the front reading does not make sense.
This way of testing will not confirm the position of the headstock in relation to the ways but in relation to the cross slide.
After it is established that the headstock is parallel to the ways it can be used to verify the cross slide in relation to the headstock.
 
The measurement on the front half should read zero and the one on the back half should read double the deviation from perpendicular.
In fact the reading he got is perfect as it is, but for the fact that the front reading does not make sense.
It does make sense if the spindle axis isn't perpendicular to the cross slide's line of travel (as with a misaligned headstock) AND if he isn't running the DI along the exact path that the cutting tool traveled from the front edge toward the center of the faceplate. It could be the angle of the photo, but that appears to be the case, assuming the cutting tool was on center.

Tom
 
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