I have a question about lathe alignment

[Mark_f]

To be honest, I think an alignment is off. The lathe cuts consistent. It does not wander when I walk by it or anything. I leveled it 3 years ago and re-leveled it last fall. It still cuts consistently the same and always has. I cant wait to be well enough to go back to the shop and check it.

 

[george wilson]

FIRST,KNOW THIS: A 9" SB lathe is a very light lathe,and the bed is quite flexible under the load of a cut. This lathe cannot operate well sitting on a flimsy floor. Especially the longer bed models @ 32" between centers. This is not to say that it is not a good lathe. But it needs to be set up properly. You also need to know how to EXPERTLY grind your cutting tools to avoid chattering,uneven cuts,and other problems. What you NEED to do,is cut a rectangular hole in your particle board floor. Dig a hole 2 FEET DEEP to fit the hole you sawed out of your floor. FILL the hole(in the ground) with concrete. Make the surface of the concrete as smooth and even as you can ! Sit your lathe cabinet on that concrete foundation and it will not move about when you are walking on that flimsy floor. Make sure all 4 feet are sitting snugly on the concrete. If not,shim the leg that needs it with a tapered OAK wedge.Then,you can properly level your lathe.

I doubt that you can swivel the headstock on a 9" S.B. lathe. The V way goes all the way under the head stock. To get the lathe so it makes a true cylinder the same diameter its full length you do not need an expensive level. You need to first make sure the tailstock is perfectly centered on the bed. Put a NEW,sharp pointed #2 MT center in both the headstock and the tailstock. Bring the tailstock right up to the headstock. Get the 2 centers nose to nose. Look straight down on them with a 10X loupe. Adjust the tailstock sideways till you can see that the 2 points are dead aligned. Look sideways at the centers too. Tailstocks can easily get worn,and become LOWER than the headstock,from being slid about. NEVER SLIDE THE TAILSTOCK over DRY ways. It will wear both the tailstock and the SOFT ways on a 9" S.B. lathe. If the tailstock center is below the headstock center,you must loosen the bolts on the sides of the tailstock and lift it so you can put shims under the top half of the tailstock. DO THIS EVENLY EVERYWHERE,or you will end up with a tailstock that may be as high as the headstock,but may be pointing downwards(which is the usual problem). To check for a down pointing tailstock,after you get the points equal in height,with the tailstock quill nearly fully retracted into the tailstock,EXTEND the quill out ,lock it,and see if the points of the #2 MY centers are STILL the same height. If they are not,you need to add shims like you did before EQUALLY on both sides of the tailstock. Do this until you can be sure that the tailstock quill is PARALLEL.You keep checking the height of the 2 MT centers from a sideways view. THEN go back to viewing from above the lathe,and make sure that the centers are perfectly nose to nose.

NOW you are ready to "level" your lathe. Put a bar of steel or aluminum in the lathe. Have it about 18" long. It is a good idea to take sone fairly deep cuts in the center area of the bar,leaving both ends the original,full diameter. Then,take a LIGHT cut off both ends of the bar. If the lathe is aligned,the ends should be the same diameter. If the tailstock end is SMALLER,put a few shims under the FRONT side of the lathe's rear foot..If your bar is too large on the tailstock end,put shims under the back side of the lathe's rear foot. Experiment with shims,repeatedly cutting the test bar,until it is the same diameter on BOTH ends.

It does help a light lathe like the 9" SB,to mount it on a 1/2" thick steel plate. Much thicker than that,and you'll need MUCH HELP even lifting the plate!! I have plates of 1/2" bronze 1' x 4'. Each one weighs 100#. And,you'll have a terrible time drilling 4 holes through a thicker plate unless you can get it onto a drill press. If you have to use a hand drill,make a smaller hole first,then drill your larger hole. It will be INFINITELY EASIER to first drill a small hole first. 1/8" diameter is fine. Removes the pressure of the center of the larger drill. The centers do not cut very well.

If you get both ends of the test bar to cut to the same diameter,try cutting the FULL LENGTH of another test bar. If your test bar is the same diameter at each end,but LARGER (shaped like a wooden barrel) in places,your lathe's bed is WORN,and needs to be re cut,re scraped or re ground. That costs big money. But you can live with it by filing long pieces till they are equal diameter all over. Short parts will likely be o.k.,unless your lathe is really badly worn.

This is the straight dope on how to get the maximum accuracy out of your light lathe.

 

[Mark_f]

I "sneaked" (snuck?) out to the shop for a little bit today ( my new test bar came yesterday). I had to try it out.

The first thing I checked is the bed for level. It is still level from the last time I leveled it and there is no twist.

Also, even though I have a crappy foundation, I see no change when walking on the crappy floor.



I put the test bar in the spindle (yes, I cleaned the MT3 taper).


This is the indicator reading at the spindle.


This is 6 inches out and it is linear. I put a flat backed button on the indicator so in case the bar sags a little, it still reads on the high surface.

I was able to get it down to .003" by loosening and re- torquing the two headstock bolts and .002" using the tailstock (which may be off).

So ...... my next step is to take the headstock loose, clean under it, and put it back and see where I am. If good ..... then align the tailstock.

 

[Technical Ted]

Just curious... if you revolve the spindle, with the end unsupported (no tail stock) does the test bar run true concentrically both up near the head stock and on the far, unsupported end? This would tell you how good your tapers in your spindle and any adapters you might have to use are running.

Ted

 

[george wilson]

If your 9" SB is a short bed one( abt 18" between centers) ,it will be more rigid than the long bed model,and may stand up to being on a non rigid floor better.

 

[tertiaryjim]

Did you mark the position of the test bar in relation to the spindle and then after testing rotate the test bar position
180deg in the spindle to confirm whats running out?

 

[Mark_f]

I think I have it.

This is at the spindle. When I rotate the spindle, I get.0005 TIR.


The other photo won't upload for some reason, but the free end is exactly the same! This is with the test bar in the spindle and no tail stock. When I put the tailstock in, it moves the bar .001", but I know the tail stock is not set perfect.

I also checked the center of the bar and it matches the ends.

What did I do to fix this? I lifted the headstock, cleaned all the surfaces, and lightly stoned the dried oil off all the mounting surfaces and washed with brake cleaner.

I don't think it can get any better. I am going to make a test cut later today.

 

[Technical Ted]

That's great Mark! Sounds like you're getting it nailed down.

Ted

 

[Mark_f]

That's great Mark! Sounds like you're getting it nailed down.

Ted

No....... I got it nailed down. I just took a .005" cut on a 1" diameter bar and cut 6" long and there is .0005" taper over the 6".

And that is in the worn area of the bed.

I am happy, happy, happy.

 

[Technical Ted]

Fantastic!

Ted