# South Bend 9b Spindle And Change Gears



## Alittlerusty (Dec 5, 2016)

3 change gears


	

		
			
		

		
	
 Rain/snow today Brrr!!and it's Monday ,perfect time to get out of the weather and do some figuring out.  Sorry about the pic orientation can't seem to get it right phone and I don't always agree. About a year ago more or less I bought a 1945ish sb9b from a somewhat unscrupulous character on Craigslist. So many lessons in such a short life lol. long story short I'm missing most of the change gears.  Skip to the bottom if u don't feel like reading  my venting I will summarize the questions I have at the bottom.  Since I've had the lathe Ive done lots of useful borings  and turnings such as repairing a snapped shaft in a pruner transmission, making some bucket cylinder pins for my mini excavator, tool holders like a Morse taper# 2 for a geometric head , some knobs and a bunch of other stuff I can't think of .  The geometric head I have will only go up to 5/16 but I do have a decent amount of chasers from 4 machine screw up to 5/16 but the most useful sizes for my little corner of the world are 1/4 " to 1".  Now that I'm more comfortable with thelathe I want to get set up to thread with it .So the gears I have are the 2-32t tumblers driving a 24t-16t compound gear, 72t-18t compound gear, 80t gear and a 60t gear. I am missing 2-32t, 36t, 40t, 44t, 46t, 48t, 52t, 54t, and a 56t. Quick interwebs search and lo and behold there they are!! except these ones are made of 24k gold by the price of them( not that bad but $200-$250 for a near complete set of the normal change gears old but look okay ) now comes the problem:  I decide to do some measuring on the gears, the spindle is 24t spline and badly worn but that's coming later. It measures 1.3"on the o.d.  so (24+2)/1.3=20 diametric pitch , measure tumblers 32t yadayada 20 dp rear stud gear same then front stud gear 16t 1" od so(16+2)/1=18 diametric pitch and the remaining 60t ,72-18t, and 80t gear are all 18dp. So someone made do with what they could find maybe atlas gears or whatever. Now there aren't any gears with different diametric pitch running tooth to tooth the change happens at the stud gear 24-16t compound one half is 20dp and the other is 18 dp. So if I buy the change gear sets online which don't have the 72-18 and the 60 or 80t gears that are 18 dp on mine I'll still be stuck. Pretty sure I'm going to buy a set of the import gear cutters and probably make an arbor for them to make a whole new set of gears tumblers and all.  Now I've been using the power feeds with the gears I do have and the spindle and the rest of the gears run fine even with the worn spindle spline and a broken tooth on the 72t gear(the gears I have can be set to about .0028 per rev on the longitudinal feed which is the second slowest feed for this lathe) I can take a deep enough cut to slow the chuck down with the belt running as tight as I think it should be without fear. So I need to buy a set of cutters that are 20dp with a pressure angle of 14 1/2 degrees. Does that sound correct??? Also my spindle is 1 1/2"-8 tpi. Eventually I'll have to replace that as well but want to get a threading first. And to be clear I won't be mass producing any threads but I have threaded 4-5 different things in the last month with hex and round dies but only have a few up to 1/2 " plus some power tapping on the mill that was cool!! I have the lathe and a Bridgeport with a 90 degree attachment for the head  a 12" horizontal rotary table with a small chuck ( no dividing plates  but  the table is a 90:1 ratio so each rev of the handle is 4 degrees and the handles  vernier has 80 divisions or 20 divisions per degree , kinda feel like I can get it close enough to work.  I plan on holding the gear blanks in an arbor  I made , I'll post more pics in a moment of the setup.  So 2 questions first diametric pitch of 20 with a 14.5 degree pressure angle based on spindle being 24 tooth and 1.3 " o.d. (24+2)/1.3= 20 DP  second question is 14.5 degree pressure angle correct kinda just assuming that  don't know or understand how to figure that .I'll ask my setup  questions in abit


----------



## Alittlerusty (Dec 5, 2016)




----------



## Alittlerusty (Dec 5, 2016)

First pic is the arbor I roughed out it's about .631" on the top where the gear blanks will go I'll bring it down closer after I make the blanks . I want a nice press fit if possible so how many thousands different do u think to keep it snug ( ill bolt them down with a washer and bolt too)? The arbor extends into the bore of the  chuck and is somewhat loose but a wrap of Teflon tape will tighten it up snug. The chuck bore is about .855" the thick part of the arbor is about 1.2" do u think this will be stiff enuff for light multiple cuts using the knee? Second pic I indicated the arbor by tapping the vise around and got it to less than a .001" as I said I'll be putting a 90 degree attachment on the mill and moving the table up and down . Also should I climb mill or conventional?


----------



## Alittlerusty (Dec 5, 2016)

I plan on making the largest gears first then turning the body of the arbor down some when I get to the smaller gears. And probably on the smaller gears the cutterwill be cutting into the arbor too . I also hope to shorten the body of the arbor mAybe an inch or so but have to get the cutters first so I can see how much room I'll really have


----------



## DSaul (Dec 6, 2016)

It was hard to make sense of that, but the South Bend 9 lathes all have 20DP spindles.  The A,B,C 9's use 18DP change gears and the double gear effects the change from 20DP to 18DP.  

(Off topic, but this was the reason I was able to change to a newer spindle in my 405 that has 20DP change gears.)


----------



## Alittlerusty (Dec 6, 2016)

Thanks for your patience  DSaul. So I will need 18dp-14 1/2pa cutter for the change gears unless I build all the gears then I could simply go with the 20 dp thruout


----------



## DSaul (Dec 7, 2016)

Sorry, I don't have any suggestions on how you should proceed.  I just wanted to let you know that your lathe having a 20DP spindle and 18DP change gears is not unusual.  The gears you currently have are probably correct and you can probably find and purchase only the gears you need on ebay.   On the other hand, there is nothing wrong with making them yourself.  That's kind of why we are all here, because we like to make things ourselves.


----------



## Alittlerusty (Dec 7, 2016)

Thanks for the clarification on the 2 different pitches on my lathe... thought I had a mutt.  Yeah I thoroughly enjoy making stuff out of nothing!  I'm not a purist nor am I restoring the lathe I'm just trying to get it fully functional so I've decided to make new gears and make them all 20 dp  then one cutter set will cover the whole gear train.  Not sure if changing from 18dp to 20dp is wise  but it will keep the cost lower. I'm going to try using some 6061 t6511 ($11 for 3/8"-3" -144") I got at the scrapyard cheap for some of the blanks. I saw a video someone did  and they seemed to holdup fine and if not I can always make them out of steel later.  Just ordered the above cutters and once they get here I'll make a holder for them.


----------



## silverhawk (Dec 11, 2016)

Alittlerusty said:


> View attachment 141002
> 
> 
> 
> ...


I would suggest using the 18DP gears, as they are standard for most 9" south bends you will find listed on ebay.  Back when you had a 9 heavy, or a junior, they were 16DP gears.  If you break one and need one quickly, you can easily find one in a pinch if you keep it at 18. Plus, you always know what will interchange, versus nonstandard. 

Sent from my SM-T217S using Tapatalk


----------



## Alittlerusty (Dec 11, 2016)

Although I agree with your recommendations etc I'm going with the 20dp for now and maybe I'll buy the 18dp cutters later to restore the lathe to original.  Meanwhile back in the bat cave the 20dp cutters arrived!  Once again apologize can't get the photos turned pretty much given up on that. I haven't figured out the formula for depth of cut yet if anyone knows offhand how to calculate that  would be much appreciated thanks for looking.


----------



## Alittlerusty (Dec 11, 2016)

That's a 32 tooth in the pics
Out of aluminum. The  arbor holding the gear blank is long enough for 2  blanks at a time , so  I'll make 2 sets at once . The arbor on the mill I made to fit a 1" end mill holder I had and the cutters are  a 16 mm keyed bore. I didn't put a key slot in the arbor just holding it with the bolt in tension seems fine in the aluminum but probably will add a key if I go for steel gears.


----------

