Newbie needs help with Logan 200 spindle runout

[SuperTroye]

Don't be afraid to do this !! This is the very first thing I ever did on any machine tool in my life, and it came out perfect, thanks of coarse, to the great guys on this forum who talked me through every step. JUST REMEMBER, make sure that both ends of the spacer you make are true to each other, as you can't trust the threads to hold the plate true.

JR, thanks for the info and sharing your experience. The issue is I don't have a proper working chuck to make a spacer. Sort of a chicken-and-egg, catch-22 scenario. Maybe I'll just turn down the spindle a few thou, that'll solve the problem

 

[Terrywerm]

Troye, I will get you dimensions of my spindle yet this evening. I don't think yours is special or anything like that, but rather that you ended up with a back plate that is not machined for a Logan despite having the correct thread. I will get pics of my spindle and of one of my chucks and post them in the next little while. I've got a couple of other things that need my attention first, but I will get this info for you as well.

 

[Terrywerm]

Okay, here are the photos and dimensions that I promised you. You will see that my spindle looks just like yours and that the chuck backplate has a relief section where the thread is cut away.



Photo 1: Not the best photo I've ever seen of a spindle.




Photo 2: Photo of the back side of the backing plate on my 6" three jaw chuck. The ring where the backplate butts up against the spindle is clearly visible.




Figure 1: Drawing of Logan 200 spindle with dimensions on my lathe.


Since the drawing saved at such a small size, here are the dimensions listed:
Diameter of spindle threads and area without threads: 1.504"
Length of spindle at thread diameter: 1.009"
Distance from registration boss to first thread: 0.217"

 

[Briney Eye]

The serpentine belt that I put on mine is marked 6PK1015 400K6. I think I picked it up at Auto Zone. It's a perfect fit and works extremely well.

 

[SuperTroye]

The serpentine belt that I put on mine is marked 6PK1015 400K6. I think I picked it up at Auto Zone. It's a perfect fit and works extremely well.

Thanks Briney Eye, I see the consensus is a 40" belt. I got the one Terry recommended with 8 ribs and it really makes things quiet.

 

[SuperTroye]

Since the drawing saved at such a small size, here are the dimensions listed:
Diameter of spindle threads and area without threads: 1.504"
Length of spindle at thread diameter: 1.009"
Distance from registration boss to first thread: 0.217"

Terry, thanks so much for the measurements. I measured mine and the spindle register is 1.529" and the thread is 1.490". So, comparing that to yours and T.J.'s I would say it's a lot bigger. See video. Without machining, I would assume at this point no chuck will fit. The Buck/Logan chuck is 1.511"

I am seriously considering turning it down. Bad choice?

 

[Terrywerm]

Don't machine the spindle, it is fine. You need to machine your chuck backplates to fit your spindle, which is standard procedure. You always fit the tooling to the machine, not the other way around. If you machine the spindle to where one chuck fits properly, you might have a faceplate or something else that will not fit properly. Look at the back of your chucks, they should have a recess in the back like the photo I posted. That recess is machined to fit a specific lathe, in the case of the chuck in the photo, it is machined to fit mine. Contrary to what some believe, threaded mount chucks do not all interchange perfectly with just any old machine that has the correct thread.

 

[Terrywerm]

If you plan to keep those chucks to use with a lathe other than your Logan, do not machine them to fit the Logan.

 

[Terrywerm]

Okay, I went back through this thread and looked at your video of your chuck backplate. There is a relief cut in your backplate, but it appears that it is not large enough in diameter. What you need to do is:

1. Remove the backplate from the chuck again.
2. Mount the backplate onto the spindle backwards - with the register counterbore towards the tailstock. You will also need a spacer sleeve with parallel faces between the spindle boss and the front face of the backplate.
3. Bore out the counterbore just large enough that it will fit onto your spindle.
4. Once it fits properly on your spindle, you can mount the backplate onto your chuck again.When you mount the chuck to the backplate, barely snug the bolts
5. Mount the whole thing on the lathe, getting the backplate snugly tightened up against the spindle. Snug, not tight!
6. Set up your dial indicator to run on the outside of the chuck body.
7. Rotate the chuck by hand to find out where you are off.
8. Try lightly tapping the chuck body at the appropriate 'high points' to get it centered with the spindle.
9. Once you have it properly positioned, tighten the bolts that hold the chuck to the backplate.

Keep in mind that backplates also have a registration land on them for centering the chuck body. In many cases the registration land is a poor or slightly loose fit to the chuck body and you will have a little bit of room available to try to center the chuck on the backplate.

Another way to center the chuck body on the backplate is to mount a truly round rod in the chuck jaws and indicate off of that instead of the chuck body. This is generally a more accurate method, but due to the way that scroll chucks wear, it is only accurate for the diameter of the rod that you used to indicate with.

 

[JR49]

Mount the backplate onto the spindle backwards - with the register counterbore towards the tailstock.

TerryWerm, I agree with your entire process, except one thing. 99.9% of the time, I will certainly defer to your expertise over my very limited experience, but I am sure he needs to have a spacer with parallel (true?) ends to span the distance between the spindle register and the front (which is backwards) of the backplate. Unless of course, you think the backplate will screw on far enough to mate up to the register without the spacer. Otherwise, you're depending on the threads alone to hold the backplate true, which aint gonna happen. Please correct me if i'm wrong

The issue is I don't have a proper working chuck to make a spacer

SuperTroye, When I made my spacer, I had no other chuck, like you. I found a piece of iron pipe that would slide over the spindle threads and hit up against the register, and cut it long enough fill the gap between register and how far I could screw on the backplate without damaging the threads. then I used a file to trim the two sawcut ends until I could put a machinist square all around the circumference of the pipe,and see that the ends were square?, parallel?, true? (whichever word fits). It took a little time to get it perfect, but was worth it in the runout reduction of the chuck. Oh, should have said, leave some extra length in the spacer for filing it true. Good luck, JR49