Back Gear Operation Atlas 10f

[navycwo]

I have been reading a few lathe books to get educated on lathe operation. The back gear operation and pin operation is easy to understand in the books. The books say that when the back gears are engaged a reduction of speed at which the mandrel is turned is obtained. It also states that when the back gear pin is engaged to the pulleys they also become locked to the mandrel thus giving a direct drive. I'm confused with the called back gear pin, isn't it the same as the indexing pin?? When I engage either on my machine one or the other or both together the mandrel becomes locked, can not turn chuck/mandrel by hand. At this point I'm afraid to turn lathe on because I'm afraid it would strip the gears.
My question; what is the problem, how to fix, should the back gears rotate on the shaft? Help

 

[kd4gij]

The indexing is just to lock the spindle. When you engage the back gear pin you have to take the lathe out of back gears. that is for the higher RPM's. That pin is disingaged while in back gear.So when you push that pin in move the back gear lever back to disingage it.

 

[RJSakowski]

I have a Craftsman (Atlas) 6" lathe and there is a pin mounted in the forward gear that engages the pulley for direct drive. For low speed, loosen the set screw and pull the pin out enough to permit the gear and spindle to rotate freely. To engage the back gears then rotate them into the spindle gears. Don't forget to retighten the set screw so the pin does not work back in or come completely out. There should be to detents on the pin to position correctly in either position. If the pin and the back gears are engaged, the spindle is locked. I use that position for locking the chuck when I am threading or similar hand operations. You can also use this to lock the spindle when changing chucks.

 

[navycwo]

The indexing is just to lock the spindle. When you engage the back gear pin you have to take the lathe out of back gears. that is for the higher RPM's. That pin is disingaged while in back gear.So when you push that pin in move the back gear lever back to disingage it.

So the index and back gear pins are two different pins, correct? Forward gear, which gear is this? Just looked in book, shows pin that is in headstock casting that engages holes in rear of pulley and calls it back gear pin. I can't find any mention of an indexing pin. Are we talking about two different pins?

 

[RJSakowski]

Your lathe may be different than the 6" lathe but here is a photo of the headstock. The pin for engaging/ disengaging the direct drive is circled in red. It is in the direct drive position in the photo. The indexing pin is circled in blue. The location of the setscrew which locks the direct drive in or out is circled in black. By forward gear, I meant the gear closest to the chuck.

When the drive pin is disengaged, the belt drives the pulley which is pinned to the rear gear (away from the chuck to the left of the belt). That gear engages the back gear set at the top of the photo which drives the forward gear at reduced rpm.

The lathe spindle cannot be rotating while the index pin is engaged.

 

[kd4gij]

The only differnce in the photo is the 10 and 12" lathes don't have the setscrew. Thay havea spring and ball that hold the pin in eather position.

 

[navycwo]

Your lathe may be different than the 6" lathe but here is a photo of the headstock. The pin for engaging/ disengaging the direct drive is circled in red. It is in the direct drive position in the photo. The indexing pin is circled in blue. The location of the setscrew which locks the direct drive in or out is circled in black. By forward gear, I meant the gear closest to the chuck.

When the drive pin is disengaged, the belt drives the pulley which is pinned to the rear gear (away from the chuck to the left of the belt). That gear engages the back gear set at the top of the photo which drives the forward gear at reduced rpm.

The lathe spindle cannot be rotating while the index pin is engaged.


View attachment 96156

Your explanation and pic clear it all up for me. I thank you for taking the time to reply a and post the pick. I went out to the shop and ran the lathe with the drive pin disengaged and back gears engaged. The back gears disengage by them self, must be a problem with wear.

 

[navycwo]

The only differnce in the photo is the 10 and 12" lathes don't have the setscrew. Thay havea spring and ball that hold the pin in eather position.

Went to shop and checked, you are correct no set screw. Thank You.

 

[RJSakowski]

Your explanation and pic clear it all up for me. I thank you for taking the time to reply a and post the pick. I went out to the shop and ran the lathe with the drive pin disengaged and back gears engaged. The back gears disengage by them self, must be a problem with wear.

I had that problem with my lathe. It was a long time ago, but I believe that I increased the spring pressure on the backgear detent. The gear teeth on the large gear were worn as well and I replaced that gear with one from a now defunct Boston Gear. I don't recall the process, but it appears that I used epoxy to hold the gear on. Not what I would do now but it has withstood the test of time.
On my lathe there is a collar with a set screw holding the back gear shaft in place. There is an internal cam which shifts the gears in and out. Loosening the set screw allows you to pull out shaft out. There is a ball and spring which provides the detent to hold the shaft in position. Either may be worn. The depression that the ball drops into may be worn as well and you may be able to rework that for a more solid detent. Worn gear teeth can also cause it to jump out of gear.

 

[navycwo]

I had that problem with my lathe. It was a long time ago, but I believe that I increased the spring pressure on the backgear detent. The gear teeth on the large gear were worn as well and I replaced that gear with one from a now defunct Boston Gear. I don't recall the process, but it appears that I used epoxy to hold the gear on. Not what I would do now but it has withstood the test of time.
On my lathe there is a collar with a set screw holding the back gear shaft in place. There is an internal cam which shifts the gears in and out. Loosening the set screw allows you to pull out shaft out. There is a ball and spring which provides the detent to hold the shaft in position. Either may be worn. The depression that the ball drops into may be worn as well and you may be able to rework that for a more solid detent. Worn gear teeth can also cause it to jump out of gear.

The gear teeth are in good shape. Where is the ball and spring located if you remember, Is the spring in the casting side or bottom pressing the ball against the shaft, and will it fall out when removing the shaft? Is it at the side with the big or small gear?