Lathe spindle alignment

[dahui]

What is the best way to check the alignment of the lathe spindle and is there any way to adjust it? Run a test indicator inside the spindle bore? I havne't bought one yet.

I'm finding a consistent change in diameter of .004 over 2.0 inches when turning a piece of 2.5" stock (unsupported/inserted full depth in the 3 jaw). I've checked the runout of my 3 jaw with a piece of drill rod and actually get about .0015 at 4 inches from the face of the chuck. This would seem to indicate that things are pretty good...without actually telling me if the spindle is parallel to the ways.

I guess the issue is between runout of the spindle and parallelism between the spindle and the ways. Haven't really thrown my brain at this one yet...guess I was hoping someone had already done the work for me!

thanks in advance

[pfarber]

Not a machinst by trade by mount some barstock using the tailstock (thick enough so you do not need a steady rest) and take a cut from tail to head, at least 6 -12 inches.

Measure the diameter at several points. You are looking to see if you are tapering the bar, if so then *something* is out of line. Your tailstock could be off center, a dirty ???.

If you adjust something just remount the bar, take another cut and check for taper.

[mxwrench]

I have had my el dorado for about 4 years now and I originally bought the complete cnc package with dro. Everything came installed. I have experienced all the same issues most of you have had and been able to solve them.

As for the lathe spindle alignment... I did the same check that pfarber is reccomending. I used a 1 1/2 aluminum barstock about 12 in long and made slow smooth passes to check taper. I was getting about .012 taper over 6 in. which was very unacceptable!

The actual problem is that the whole upright portion of the machine is not aligned with the ways very well. To make matters worse it is pined with tapered alignment pins from the factory. (remove the paint to see the pins).

The solution for me was to remove one of the pins (the one on the operator side) and loosen the bolts holding the main upright. Then move it slightly in the direction required with a big bar and tighten bolts down and recheck taper on barstock.

Lastly, I tapped the tapered pin back in until it lightly seated (with the upright bolts still very tight). The tapered pin sticks out about 1/8 in, after I achieved proper alignment with the ways! But now I can turn stock 10" and only get about .0015 taper! It took me 2 years of machining parts and pulling my hair out to figure out that this was the problem with the machine, but now all my projects seem to come out much closer to plan (using mach 3 cnc)

After this last mod I am finally in love with my machine again. The surface finish is MUCH better after fixing this problem. Still not the best finish mind you but much more acceptable than before.

I don't know if this problem was specific to my machine or if more of you are experiencing the same issues as I was, but it is an easy check to see if it is off. Just not so easy to correct!

Good luck and if you do have to correct the problem as I did, the tapered pin is quite difficult to remove (location) so try making a small puller (the pin has 5mm threads in its center) and draw the pin out with a jam nut.

BK

[dahui]

Now that's what I call a first post! Welcome to the boards.

Actually, I was turning 2" and 2.5" stock when I discovered that I was getting a taper, so I may in fact have an alignment problem. I need a close sliding fit over about 2" so missalignment would certainly explain my results.

As far as the "pin" in question, I looked at my machine and see two "thingys" (one on each side) between the mounting bolts for the lathe spindle. I checked the threads with a 5 x .8mm screw and it seems to be threaded but it tightens up real fast. Either the wrong pitch or just gunk in the threads...any idea what the pitch might be? Screwing up that thread would make more work than I'd like to put in.

Also, since you have been using your machine for a while, do you observe any rotation (of the table) when you move back and forth on the X axis?

Thanks much for the info! Right now I'm trying to tram the mill head so I'll have to get to the lathe next.

[mprotec]

If I may share my two cents,...I think the simpler way is to machine the flange that you lock your chuck to. Meddling with the pins and so forth might create other problelms... eg. strength of the spindle mount.. thicker cutting will be a problem later on.
Moreover getting it done properly is definitely a heavy task.. to achieve what max has done is an accomplishment...
Hope that helps...

[dahui]

I might try machining the flange but my table rotates and I'm not all that confident I can make a perpendicular cut over that large a radius. It's just hard to tell if it's the chuck or the spindle...might have to break out the 4 jaw. If that is "in" then there should only be the spindle left, in terms of error, right?

[cut more]

Dahui,
You did not mention whether your lathe bed has been levelled and checked for tru-ness after mounting on your bench or stand. Just placing the lathe on a stand & tightening the bolts can twist the bed enough to make it a tapering lathe.
Check out the 9x20 yahoo website. There is a lot of info there.
On the 9x202 web site there is a file called rebuilding the asian 9x20 lathe. read that also it may help.
Cutmore

[scbvideoboy]

I got mine in 2005 and tons of issues, I have a ongoing post here about excessive runout with the chuck and precision ground round SS stock.

I could actually push on the chuck and get major defection. I was told to take the spindle pully nuts off and tighten the lock rings to remove excess play. That helped a LOT on the chuck defection.

A while ago I started to do long stock and was seeing taper type cuts, I ended up moving the tailstock a hair to correct it, now it's within my tolerance of under 2 thous.

On this machine EXPECT to spend lots of time fiddleling with the machine to correct all those issues from assembly and shipping.

After spending a year with this machine, there are just too many design flaws that pop up that prevent any positive feedback.

I am not a professional, zero training, but I have never been happy with the finish cut as well.

My newbie advice is to see if you can hire a pro machinist to come over and go through the setup.

Oh NAPA has green 3/8 wide industrial type belts that work much better than stock.

One thing I REALLY hate is to have to buy tools and goodies everytime I start a different project, next up, the rotary table.

Dave

[dahui]

Dahui,
You did not mention whether your lathe bed has been levelled and checked for tru-ness after mounting on your bench or stand. Just placing the lathe on a stand & tightening the bolts can twist the bed enough to make it a tapering lathe.
Check out the 9x20 yahoo website. There is a lot of info there.
On the 9x202 web site there is a file called rebuilding the asian 9x20 lathe. read that also it may help.
Cutmore

That's an excellent point and no, I have not checked it. Now that you mention it, my chip tray is far from flat. It seems like the box sections should help keep the mounting points aligned, but I suppose even a tiny twist will be magnified. Now I have to build a new bench? That should be an adventure.

I'll try and find the yahoo group. Thanks a lot.