# Back Gears Setscrew



## MikeMc (Jun 15, 2015)

The problem with the setscrew in the back gear spindle is written about often and I found out last week that some PO of my lathe over tightened it scoring the shaft so that to replace the bushings I'll have to groove one just to get it apart.
    To keep me from doing the same one day when my mind is on other things I replaced that setscrew with a 1/8" panhead and was wondering if anyone else had done so on their lathe?
I plan on replacing the spindle pulley setscrew with a flathead screw but have to figure out how to hold it to turn the head down first.
Mike


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## RJSakowski (Jun 15, 2015)

MikeMc said:


> The problem with the setscrew in the back gear spindle is written about often and I found out last week that some PO of my lathe over tightened it scoring the shaft so that to replace the bushings I'll have to groove one just to get it apart.
> To keep me from doing the same one day when my mind is on other things I replaced that setscrew with a 1/8" panhead and was wondering if anyone else had done so on their lathe?
> I plan on replacing the spindle pulley setscrew with a flathead screw but have to figure out how to hold it to turn the head down first.
> Mike


What appears to be a set screw on my 6" Sears/Atlas is actually a lube port plug.  The back gear is meant to be free rotating held in place by the frame and spacers.  The screw should not contact the shaft.


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## wa5cab (Jun 15, 2015)

That is what he was explaining.  As with the oil plug/set screw in the spindle cone pulley, sometimes  PO's screwed them in too hard and gouged the spindles. 

The 10F parts list does not list or show the screw but the later 12" list does.  Perhaps some PO's, thinking that the screw was too short, deliberately installed a longer one.


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## RJSakowski (Jun 15, 2015)

wa5cab said:


> That is what he was explaining.  As with the oil plug/set screw in the spindle cone pulley, sometimes  PO's screwed them in too hard and gouged the spindles.
> 
> The 10F parts list does not list or show the screw but the later 12" list does.  Perhaps some PO's, thinking that the screw was too short, deliberately installed a longer one.


I assumed that a PO had put a longer screw in.  I believe that the 1/4"  long r. h. screw in my back gear is OEM but I can see where someone would mistake it for a set screw.  The Sears user manual makes no mention of the screw other than the parts list.


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## RJSakowski (Jun 15, 2015)

MikeMc said:


> I plan on replacing the spindle pulley setscrew with a flathead screw but have to figure out how to hold it to turn the head down first.
> Mike


Mike, drill and tap a short length of round stock  and mount your screw in that.


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## Round in circles (Jun 16, 2015)

Going on with the lube part of the thread . 
Can anyone tell me what the thread form & TPI  that there is on the USA's  Atlas lathes that have screw down grease cups caps to lube the head stock taper roller bearings .

 I ask because I want to replicate the thread on mine on a reasonable quality steel bar to make an extending shoulder so I can then  drill and tap the extender shoulder for it to take a metric grease nipple .

 This will be my first attempt at  thread cutting on the lathe for the grease cup thread on the extender , I have a metric  grease nipple tap for the other thread . 

Perhaps you'd also be kind enough to explain the breakdown of how you write the thread form and size details plus give the thread angle as I don't have a USA thread gauge .


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## louosten (Jun 17, 2015)

Greetings;
I know what the back gears are supposed to be used for...but who really uses them and for what purpose?
Thanks in advance for responses,
Lou O.


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## John Hasler (Jun 17, 2015)

louosten said:


> Greetings;
> I know what the back gears are supposed to be used for...but who really uses them and for what purpose?
> Thanks in advance for responses,
> Lou O.


I use them frequently on my Logan 400 to get lower speeds (which aren't slow enough, which is why I intend to convert to a DC motor some day soon).


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## JimDawson (Jun 17, 2015)

Many many years ago when I had my Craftsman Commercial 12x36, it pretty much spent it's entire life cutting Inconel, so it lived in back gear.  It was really not enough lathe to do what I was doing with it, and I pretty much wore it out in about 2 years.  It did make me enough money to to buy a new 14x40 gearhead and a new Bridgeport clone so I can't complain.


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## mattthemuppet2 (Jun 17, 2015)

back gears = lower speeds without losing torque. Very useful for turning large objects (like chuck back plates) or perhaps work hardening steels where the surface speed would exceed what is recommended for the cutter. I wiped the nose off an HSS cutter in an instant truing up a 4in back plate at 800rpm - put it in back gear (100rpm for that pulley?) and it cut just fine. Also recommended for threading to a shoulder so that you have more time to open the half nuts before crashing the tool into the shoulder.

To be honest, if there's room and you have the skills/ tools I'd replace that screw with a knurled knob. You're supposed to oil the back gear pulley every time it's used and for me at least it would be way easier to have a tool free way of doing so.


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## Ulma Doctor (Jun 17, 2015)

i use the back gears on all my lathes, especially when threading and boring large holes in larger work.


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## wa5cab (Jun 17, 2015)

Round in circles said:


> Going on with the lube part of the thread .
> Can anyone tell me what the thread form & TPI  that there is on the USA's  Atlas lathes that have screw down grease cups caps to lube the head stock taper roller bearings .
> 
> I ask because I want to replicate the thread on mine on a reasonable quality steel bar to make an extending shoulder so I can then  drill and tap the extender shoulder for it to take a metric grease nipple .
> ...



David,

The short answer is "none".  After some careful research, AFAIK no US built Atlas lathe ever used screw-down grease cups on the spindle bearings.  All of them, whether bronze sleeve, babbit, tapered roller or ball, used oil cups.  In later years (and recommended for retrofit), felt plugs were added to regulate the oil flow.

The only usage of grease cups that I can find on any Atlas lathe is on the 10" vertical and horizontal countershafts, where the bearings were straight roller and no seals were provided.

Most Atlas tapered roller spindle bearings have survived for anywhere from 35 to 80 years using oil applied every day.  Modifying something that works just fine is never a good idea.


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## Round in circles (Jun 18, 2015)

Thanks Robert,
I kind of guessed that the Atlas lubrication system would be oiler pots through out  as that's all that I've seen on the various video clips .

The reason I wanted  to convert the cups & grease arrangement to a simple once a day small shot of grease out of a hand held small grease gun into the grease nipples is that I have sugar diabetes & it is affecting my finger sensations amongst other things.   I can't always be sure I have hold of small things , so trying to put the grease filled brass cap back on the fine brass thread is difficult to say the least ,  on several  occasions I've dropped them  into the head stock casing .  The cups on my lathe are set at an angle of about 15 degrees to the vertical  facing outwards unlike the oilers which always appear on the videos to be in the vertical .

Are the Atlas Oilers  a parallel thread or are they a taper thread  ?
The threads in my  taper roller bearing caps where the grease cups are fitted on my Sphere  lathe appear to be fine parallel threads , not tapers as is usually found on old imperial British grease nipples of the 1940 's & 50's . Both the cups & the caps are made of brass.


I should be able to make simple oiler cups with a decent sized plastic push on cap . I can easily  make my own felt washers out of the felt that is used to protect wooden floors from dining chair legs or perhaps raid the first aid box and take a bit of medical grade felt from it etc. etc.

Are you able to tell me what thread form , depth and size I need to make to see if the threads are the same as the USA  Atlas lathe oilers ?

  Now for a laugh .
I had a bit of a scare this afternoon . I'd been turning some drawn steel pipe , stopped the lathe to check with the calipers to see if I was getting close and then do the maths for the final cuts .

I found I only had 8 thou to go so I set the cross slide reference dial to 3 thou to get things down ready for the final light fine finish cut .

For a while now I've always been starting the lathe whilst it is not engaged through to the chuck so as to keep the load on the motor light & reduce wear on the old worn phosphor bronze cross shaft bearings .
Replacing them with sealed for life high speed roller bearings is my next project of the day  ....hopefully .

The lathe motor started but the chuck would not rotate as I gently the lathe into drive . Puzzled I tried it again and realised that the headstock was rock solid .

Heart in mouth and hand on wallet,  I nigh on panicked ,  as over here a  pair of shouldered taper rollers are not the cheapest of bearings  .  Then as I looked for hot bearings or some obvious fault I realised that the locating  pin that locks the bull gear had been knocked in and was holding the the head stock spindle locked up solid.

After calling myself several delightful names and laughing at my own stupidity ,  I decided to have a look at the reason that the pin had engaged.

I rotated the pin ( discovered that  last year when I got the lathe ) to take it out  .  So that the bearing & spring were compressed , then carefully  slid the pin out as I covered the the top & inboard side holes with finger & thumb to retain both ball  bearing and spring .

I found that the 1/4 inch dia locating pin has a half inch segment milled out the middle to a depth of about 1/8 of an inch .  ( didn't think much about it last year when I took it out )
There are no grooved rings on the pin that would locate on the ball bearing under spring pressure so the pin cannot  slide in or out at the slightest  touch .

Is this milled out pin the correct one  or has someone made their own pin and messed up , that it should indeed have two locating grooves on it instead?


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## Round in circles (Jun 18, 2015)

mattthemuppet said:


> back gears = lower speeds without losing torque. Very useful for turning large objects (like chuck back plates) or perhaps work hardening steels where the surface speed would exceed what is recommended for the cutter. I wiped the nose off an HSS cutter in an instant truing up a 4in back plate at 800rpm - put it in back gear (100rpm for that pulley?) and it cut just fine. Also recommended for threading to a shoulder so that you have more time to open the half nuts before crashing the tool into the shoulder.
> 
> To be honest, if there's room and you have the skills/ tools I'd replace that screw with a knurled knob. You're supposed to oil the back gear pulley every time it's used and for me at least it would be way easier to have a tool free way of doing so.




 A somple har rubber plug that chan be pushed in 7 pulled out is  one way it can be done. 

I checked my Sphere lathe today it does not have anything over the hole nor is it threaded.

 Which made me think of the older pre 1960's bicycles .
On the spindles there was a dimpled spring clip that could be rotated or slid to one side to allow you to put a few drops of oil inside the spindle  so it could lubricate & clean the bearings as you rode your bicycle .  
When you reassembled these old type wheel bearings you were supposed to use white grease to lightly pack the balls into the cups & then the weekly put a light oil in the spindle hole which would clean them out by centrifugal force as you rode around.


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## wa5cab (Jun 18, 2015)

Round in circles said:


> Thanks Robert,
> I kind of guessed that the Atlas lubrication system would be oiler pots through out  as that's all that I've seen on the various video clips .
> 
> The reason I wanted  to convert the cups & grease arrangement to a simple once a day small shot of grease out of a hand held small grease gun into the grease nipples is that I have sugar diabetes & it is affecting my finger sensations amongst other things.   I can't always be sure I have hold of small things , so trying to put the grease filled brass cap back on the fine brass thread is difficult to say the least ,  on several  occasions I've dropped them  into the head stock casing .  The cups on my lathe are set at an angle of about 15 degrees to the vertical  facing outwards unlike the oilers which always appear on the videos to be in the vertical .
> ...



David,

All of the US Atlas lathes use press-in oil cups or oilers.  They were originally made by a company named "Gits", and are or were often referred to as "Gits Oilers".  This includes both straight and right angle oil cups with spring-loaded cap and spring-loaded ball oilers.  The holes are unthreaded and parallel sided.

The threads on your Sphere are probably "British Standard Pipe Threads for Non-Pressure Tight Joints".  This was primarily intended for mechanical assemblies (frames and the like) using pipe as a structural member.  The thread form is Whitworth (55 deg.).  1/16" and 1/8" are both 28 TPI.  Major diameters are 0.3041" and 0.3830".

If the grease cups on the Atlas countershaft are screw-in, they are most likely 1/8" NPT but could be 1/16".  These are tapered threads and both are 27 TPI.  The pipe OD's are 0.405" and 0.3125".  You can buy hand dies in these small sizes which is what I would recommend you do.





> After calling myself several delightful names and laughing at my own stupidity ,  I decided to have a look at the reason that the pin had engaged.
> 
> I rotated the pin ( discovered that  last year when I got the lathe ) to take it out  .  So that the bearing & spring were compressed , then carefully  slid the pin out as I covered the the top & inboard side holes with finger & thumb to retain both ball  bearing and spring .
> 
> ...



As just discussed yesterday and today in another thread, the 6" lathes have a direct drive lock pin with two circumferential grooves for a spring loaded ball to drop down in.  The 10" and 12" have a round pin with a flat milled on one side.  Instead of a spring loaded ball bearing, they have a spring loaded ball nose pin.  You rotate the lock pin until the ball pin is clear of the flat in order to remove the lock pin.  The lock pin is held in either of the two operating positions by friction.  The ends of the flat provide a hard stop or position indication.  So I would have to assume that your lock pin is probably original.


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## Round in circles (Jun 18, 2015)

Thanks Robert ,
I've just posted on the bother thread how I did things with the lock pin .

I've decided I will however be modifying it so it has two fairly deep positive locating annular grooves  ,one for pin in & one for pin out.   It  will also have a shoulder with fair sized knurled knob on it so it is easier to pull out and also maybe a spring " U " type small tool clip or an " R " clip on a few links of very small chain so it wont get " accidently "  pushed in so easily again .


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## wa5cab (Jun 18, 2015)

David,

The problem with your fix appears to be two-fold.  One, you used a spring and ball smaller in diameter that the original and a spring longer than the original.  Two, you used a ball instead of a round nosed pin.  All of these changes result in less holding power than the original.  And the first one results in very easy movement of the spring around in the hole.  

You should not ruin the lock pin by drilling dimples in it.  You should find the pieces of the original spring and reconstruct the original length and number of turns, and find an equivalent replacement.  You should also find the original ball nose pin and make a replacement the same diameter and length.  Once you have done those things, you will have a lock pin that behaves according to plan.  And which in 30+ years has never misbehaved.


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