I have a question about lathe alignment

[4GSR]

Mark and others out there, the taper in the 9" SBL is not a true MT3. The taper is off by a few thousandths per inch. So the indicator reading you were getting at 6" out is about right for a test mandrel not fitting the taper properly. Bump it around by hand until you get it running true out on the end.

Like I said in my post earlier in this thread, Leave the bolts loose on the tail end of the bed and somewhat tighten the bolts at the headstock end of the bed. This is the way my 9" SBL has been setup and running since 1949 when it was born. It cuts within .001" in two inches without using the tailstock. With the tailstock, I have not checked it since I recondition the lathe about 15 years ago.

 

[Mark_f]

Mark and others out there, the taper in the 9" SBL is not a true MT3. The taper is off by a few thousandths per inch. So the indicator reading you were getting at 6" out is about right for a test mandrel not fitting the taper properly. Bump it around by hand until you get it running true out on the end.

Like I said in my post earlier in this thread, Leave the bolts loose on the tail end of the bed and somewhat tighten the bolts at the headstock end of the bed. This is the way my 9" SBL has been setup and running since 1949 when it was born. It cuts within .001" in two inches without using the tailstock. With the tailstock, I have not checked it since I recondition the lathe about 15 years ago.

Well ....... I can now cut 2" without the tailstock and the taper is negligible. I set the tailstock and can cut 6" with less than .001" taper. I will see how long it stays. My lathe bench top is made of 1/8" steel plate. The sides are 1" high at a 45 degree angle. It was designed to run flood coolant.

If the spindle is not 3MT , it must be mighty close because the 3Mt tooling I have fits good, sucks in tight and doesn't move. It doesn't "bump" around.

 

[4GSR]

Mark, i eat my words, I was confusing myself with the no. 4MT and not the 3 MT. I went back and looked at the SBL book "How To Run A Lathe" in the back at the table of dimensional data and verified, it is the same as 3MT. Sorry.

 

[Mark_f]

Mark, i eat my words, I was confusing myself with the no. 4MT and not the 3 MT. I went back and looked at the SBL book "How To Run A Lathe" in the back at the table of dimensional data and verified, it is the same as 3MT. Sorry.

No problem. I thought it was a 3MT, but I been wrong before.

 

[4GSR]

What it was, the larger SB lathes, with 1" collet capacity, most of the spindles have a taper that is about 1.625" diameter at the face with a .603 TPF. This is not even close to the taper in my 15" Sheldon lathe. It measures 1.625" at the face, but the taper is equivalent to a 5MT which is .6315 TPF. This is what I was thinking was the difference on a 3MT. As the saying goes, "start brain before mouth!" I need to go eat some more brain food......

 

[Technical Ted]

You guys have probably seen this before, but I thought it might be useful for those who haven't. My 1935 15" SB is the same as the 14-1/2" with 3/4" collet in the attached. The taper is the same taper per foot as a #3 morse but is a larger diameter requiring a special adapter to actual morse taper sizes. You can buy an adapter, but I made my own and it works perfectly. It's nice that your 9" can use a #3 directly without the need for such adapter. The more adapters needed, the more room for error and mis-alignment.

Ted

 

[4GSR]

Yep, that is the same page that is in the SBL book "How To Run A Lathe".

 

[Mark_f]

I am putting this here in hopes it maybe useful to someone else.

I bought my South Bend 9 lathe in 2013. It was all original and I new the history of the lathe. It is a 1944 model B. It was a war surplus machine bought after the war by a guy I know and passed to his son and then I bought it. It was never dismantled , restored, or repaired. It was as original and setup and used "lightly" ( they are not machinists. When I moved it to my shop, I set it up and leveled it. I used it for the last 4 years but it always cut that 5 to 6 thousandths taper per 10 inches. I never could figure out why. Over the years I got all kinds of advice as to why and a lot of it made sense but wasn't the problem. The headstock is mounted on a V way and not adjustable. As you can read earlier in this thread, I was tired of fighting the taper. In desperation for a solution, I lifted the headstock. All looked good. There didn't seem to be anything under it. EXCEPT ....some very old oil that had dried and made a brown discoloration on the V way. This appeared as a stain as I could not feel it... just see it. I used some crocus cloth to shine the way and the bottom V on the headstock. Fine crocus cloth will not remove any material but will clean the surface if you rub enough. I remounted the headstock and checked the alignment and the taper is almost all gone. I put a dead center in the tail stock and the headstock to hold my alignment bar between centers,adjusted the tailstock and got the alignment to .0001" over 10 inches.

I have cut several parts since doing this and all parts are no more than .0001" taper and short parts up to 4 inches have no measurable taper. All alignments on this lathe are as perfect as I can possibly get them, and with the recent upgrades to large dials and a graduated dial on the tail stock, this lathe is a dream to use.


One note here. Before I set the tailstock alignment, I used a MT2 hand finishing reamer to "clean" the tailstock socket. At the most I didn't really remove any material. Just any high spots and to polish it a little. The tools don't go in any measurable distance farther. By doing this, it has greatly improved the grip on tools inserted. I also polished the tapers on my tooling with some very fine crocus cloth. I cant believe the improvement holding tooling.

The point here is, an old oil stain that I couldn't even feel, was enough to throw the alignment off.

 

[daveghil]

Hi all....I'm new to metal machining and recently picked up a Altas Clausing 6X24 Lathe. MT2 on headstock, MT1 on tail stock. Would like to do a tune up and align the tail stock. Shopping for test bars I see two types: 1) bar with center holes on each end to be placed between centers on the head and tail stock and 2) mandrel bar with morse taper on one end for headstock and center hole for tail stock. I figure #2 would be better since I wouldn't have to account for runout on my 3 jaw chuck. I have a MT1 dead center for the tail stock and I could borrow a MT2 live center from my wood lathe for the head stock so I could avoid the chuck with either option 1 or 2. Perhaps I'm splitting hairs but I wouldn't want to be half a hair off center! Any recommendations would be appreciated.

 

[woodchucker]

Hi all....I'm new to metal machining and recently picked up a Altas Clausing 6X24 Lathe. MT2 on headstock, MT1 on tail stock. Would like to do a tune up and align the tail stock. Shopping for test bars I see two types: 1) bar with center holes on each end to be placed between centers on the head and tail stock and 2) mandrel bar with morse taper on one end for headstock and center hole for tail stock. I figure #2 would be better since I wouldn't have to account for runout on my 3 jaw chuck. I have a MT1 dead center for the tail stock and I could borrow a MT2 live center from my wood lathe for the head stock so I could avoid the chuck with either option 1 or 2. Perhaps I'm splitting hairs but I wouldn't want to be half a hair off center! Any recommendations would be appreciated.

ok, forget that buying a bar.
Take a bar and put a center hole on each side.
next
take a piece of stock, and make a center for your chuck.
you'll use it many times later.
make it less diameter in the chuck, with a shoulder in front of the jaws. Put a 60 degree taper on it (30 degree swing of compound).
mount the bar between centers. use a dog to drive the bar on the chuck.
Take a cleanup pass on the bar to get it round.
Now take a 10 thou cut across the whole length. measure ..
if your tailstock end is wider, move the tailstock toward the front,
if the tailstock end is narrower move it toward the rear.
Rinse and repeat.

edit: please don't use a live center for this effort, if the live center is off a little you have wasted your effort.

When you are done you have a new test bar. Next time you can measure using a drop indicator first.. And only take light cuts if needed.
Mark headstock end and tailstock end (not necessary, but a good practice).

Anytime you use that center you will need to take a cleanup pass to make sure it's on center again (runnout causes it to move, so you true it each time)

Now you didn't spend anything (other than material) and made some tooling.