new to a 50's south bend 9". Have some questions

[GK1918]

Mine before a paint job. I finnally got a quick change tool post. 100% better. As already said above the thread dial
being in syc. Many times we will disengauge this dial (like to disengauge the feed screw) when doing a lot of
drilling facing why have all this stuff turning and wearing. Ok so I am to thread, engauge thread dial, run machine
with half nut engauged a little bit, turn off power, now sometimes the hash marks dont line up. real quick what I did,
was I fit a large washer over the thread dial with a witness mark and simply dial in the washer to line up with the
hash marks. I really like my SB its a long bed. Too bad it doesnt have twin feed screws. My big heavy 20" has
twin feeds which means its feeding and cross feeding at the same time for doing tapers like boat shafts really just
an automatic taper attachment. Well thought of 100 yrs ago. Another good thing that works great is to put a black
sharpie in your tool post for practice (slightly under center) cheap pvc pipe. You must get a pitch gauge they are
cheap. Master left hand threading, master acme threads. Years ago always wanted to do this stuff in being just
a play thingy. No clue I could not read a yd stick. Absolutly horrible in math. All started years ago being a cop on
3rd shift maybe a loose cow call. (cops go in a lot of places) anyways I was given a SB9A on some call. Then I use
to do some details good size flea market and bought more than my pay buying stuff that looked like machiny things.
How about a taper att. for $5 try Ebay now for one I thought it was cool. All these years gone by by. I kind of mastered
this thing. Idea! why not a cheap add in the news paper. Machining emergency room for cheap. So I get involved
with a lot of left hand & right (big stuff) threading cant be found in local stores. I think I wrote this in some other
site already, bolts as big as a beer can way cheaper than Cat and no wait. Another avenue Craftsman mower deck
spindles which are totally junk. I make them for $25 with grease fittings Sears wants $60-80 and not in stock. Thats
the powers of a South Bend good luck!

 

[GK1918]

I forgot to also add

Maybe as I wrote some may not know about twin feed screws see if this photo shows notice the two clutch hand
wheels that engauge the carriage and cross feeds both forward and backward this machine made in 1918 has
change gears so it is set for 8tpi acme threads.

 

[overkill engineering]

ScrapMetal,

Thank you so much. I can't fathom how anyone could have explained it better. Much appreciated.

So a follow up question. Lets saw I am turning a piece of 2" steel and want to have a section neck down to 1.5" with a 90degree shoulder. I understand now the right way to do this is with the clutch. So I tighten the clutch and the carriage starts moving toward the shoulder. As I approach it, it doesn't seem like the clutch knob is very "quick", so is there a trick to not crashing the bit into the shoulder I am cutting? Or do you just undo the clutch well in advance and cut it in by hand?

Check out this Tubal Cain video on the apron parts...

http://www.youtube.com/watch?v=UfnZd16QXP8

This should clear up some things for you.

-Ron

 

[ScrapMetal]

Or do you just undo the clutch well in advance and cut it in by hand?

That is pretty much how it is done. There is another little item that, combined with hand advancing, allows you to stop at a consistent point for making a shoulder. You may already have one that came with your lathe. Here is one design that I found with google on the web:



Again, you would release the clutch in advance and then advance the carriage by hand until it hits the stop.

Hope that helps,

-Ron

 

[Hawkeye]

Overkill, if you refer to the second photo you posted, take a look at the picture of the headstock of the lathe. The upper left lever selects the direction of rotation of the lead screw. The center position is neutral, or disengaged. The upper position will move the carriage toward the headstock (Apron selector lever up or half-nuts engaged), or the toolholder away from the work (Apron selector lever down). The lower position will move the carriage away from the headstock (Apron selector lever up or half-nuts engaged), or the toolholder toward the work (Apron selector lever down). There is an interlock so you can't engage half-nuts if the selector lever isn't in neutral.

I used to wonder why they didn't have the feed direction lever in the same position to feed into the work for both carriage and toolholder feeds. When you think about it, it's a stroke of genius to have them opposite. If you accidentally set the apron lever to the wrong setting, the tool will move away from the work, instead of causing a crash.

Now, check out the table at the bottom of that photo. You will see a whole number over a decimal fraction in each square of the table. The whole number is the number of threads per inch that the carriage will move when the half-nuts are engaged (obviously for threading). The fraction is the distance the carriage will move for each revolution of the spindle (for turning).

When the clutch is engaged (by tightening the little star wheel) it is possible for it to slip if the going gets too tough. This is a good thing. The tool bit can't keep trying to move into the work if bad things might happen. The half-nuts, on the other hand, will NOT slip if you go too far. Always keep your hand on the half-nut lever when it is engaged and be ready to open the nuts when needed.

Crank the carriage to the middle of the ways and try out all the positions and adjustments with nothing in the chuck. Be ready to release the clutch or half-nuts before anything crashes. Learn by doing. Have fun. Count fingers regularly.