Aligning my old South Bend

Danshell

Danshell

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So I have watched several youtubers aligning lathes as I want to make sure my old SB10K is aligned and level.

There is one thing I dont understand. I have got myself a nice length of hard precision bar that I can use as an aligning bar but I need to drill both ends to hold it between centres.

So my question is, if I drill both ends on my lathe and my lathe is out of alignment then wouldn't i be putting the holes slightly off centre on the ends, so when i put the bar between centres it is going to be out of alignment anyway???

How do i get perfectly centred holes in my perfect length of bar? All the youtubers neglected to mention this part or they used bars that were already set up for aligning.

Sorry if this is a typical newbie question.
 
Hi Danshell,
There is no problem with this because when you drill the ends of the bar the bar will be held close to the chuck and drilled in the centre of rotation. You will however need to support the bar at the other end of the spindle with a spider or a plug.
Alternately if using a fixed steady you would dial true with an indicator.
There are options. There is Rollies Dad's method which takes a bit of thinking about but works really well: Rollie Dad Method - Spindle alignment on my mini Lathe from Micromark 7x14 - YouTube
From Build Something Cool: Metal Lathe 101, Tip #1: Leveling your lathe - YouTube How to leveling a Lathe - YouTube
Just a couple of thousands out there but cover just about everything you need to know.
Not everyone has machinist's levels but the above videos will show you don't need them. I'd leave the final checking to turning collers after going though the basics as are explained above.
Most importantly do not get frustrated and as Guy Martin would say "Always have a cup of tea handy".
 

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Danshell said:
So my question is, if I drill both ends on my lathe and my lathe is out of alignment then wouldn't i be putting the holes slightly off centre on the ends, so when i put the bar between centres it is going to be out of alignment anyway???

How do i get perfectly centred holes in my perfect length of bar? All the youtubers neglected to mention this part or they used bars that were already set up for aligning.
Click to expand...


I'd like to try and answer your question because it bears on a basic topic that different guys might have different views on.

In my opinion, and its just an opinion, the very first thing to be done when setting up a lathe is to align the headstock. There are a number of ways to do this and these are just the ones that I'm aware of:
  • Rollie's Dad's method as noted above. This one has a lot of adherents but also many detractors. Look into it.
  • Facing - basically, you take a rod at least 1-2" OD and face it, then use a dial indicator and sweep the face. You must sweep in front of center and in back of center. If the headstock is off, the front and rear will differ. Actually, what you'll find is that the front will read flat but the rear will read off. Then you need to adjust the alignment of the headstock until both read the zero deviation. This method actually works.
  • Morse taper test bar - you buy an alignment bar with one end having a taper to match your lathe. Lots of guys use this one. My problem with it is two fold. First, it relies on the Morse taper of the bar and the lathe being accurate, which is unlikely. Second, you have gravity acting on that bar all the way down its length and that is going to result in a tiny bit of sag.
  • Finally, you can cut a test bar. Put a piece of 1" mild steel, like 12L14, into your 3 jaw so that you have 4" sticking out. Use a sharp HSS tool to take a 0.010" deep cut all the way down the bar to take off the skin. Then take 0.003" off all the way down the bar, then repeat with a 0.001-0.002" deep cut all the way down the bar. Measure the end and up near the chuck. If there is a difference, move the headstock until the difference resolves with further test cuts. Of all the methods above, I prefer this one because it produces a cut using the cross slide that is riding on the actual ways of the lathe. If the headstock is off relative to the ways, this test will show it. Make whatever adjustments to the headstock that are necessary to resolve any deviation. It also follows that when the headstock and the ways are aligned the lathe will cut a true cylinder on a very short unsupported test piece like this.
Now, once your headstock is aligned, it is a simple matter to cut a test bar small enough to pass through the spindle bore of your lathe. You can use your 3 jaw for this. Choke up on rod so you have a very small amount of stick out and face it, then center drill it. Flip the rod around and center drill the other end. Voila, two ends drilled accurately. A test bar used between centers is only useful for aligning the tailstock after the lathe is leveled so do that first.

Hope this provides some food for thought.
 
I will be following this with interest as I will have the same issue once I get my 9A securely mounted to the floor.
Thanks for posting this!
 
Not to bust up your day, but if there is wear on your ways the lathe will always want to cut slight tapers on longer pieces, usually getting wider towards the tailstock. You can attempt to adjust this out for one length but will have problems elsewhere.
 
Thanks very much for all the replies. Ill do a proper leveling and alignment in the near future.

On the weekend I put a long piece of stock from one end of the lathe to the other, held it in the 3 jaw and supported it with a dead centre at the other end. It was 32mm stock. I ran a clean pass the whole length (I am practicing my tool grinding) and for a test I decided to measure it.

It was .2mm larger at the tail stock end. I am not sure what this really proves at this stage but until I need to machine something with any real accuracy I dont think the old girl is too bad.
 
I like to initially evaluate the headstock alignment separate from the tailstock alignment. I try to chuck it as flat to the jaws of the chuck as possible (spin the round stock as you tighten the jaws on the chuck). Then I do a light pass over the length (till smooth). Then I measure the rod for taper (take a micrometer to it and see if the diameter of the rod goes up/down/stays-the-same over the entire length). The rod growing more narrow or more wide is an indicator your headstock is out of alignment. Errors which are horizontal affect the diameter more than vertical errors (i.e. a 1/1000 error over 12 inches which is horizontal will cause more change in the rod stock size, than1/1000 error pointing up or down.

You can then put an indicator against the SIDE of the round stock, zero it, and slowly move the tail stock forward (with a center) into the drilled hole on the end... did it move? Withdraw the tail stock, move the indicator to the TOP of the round stock, once again slide the tail stock (with a center) into the drilled hole... did it move? If it didn't move, then the tailstock and the chuck/spindle is aligned with the tail stock. If it moved, then they spindle and tailstock are not aligned. Always align the headstock first, then the tailstock second.

Note, this is NOT a full alignment technique, this is the cliff notes version to see IF you have an alignment issue.
 
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